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Vegetative top dry weight (DW), leaf DW, stem DW, and stem diameter of mature eggplant plants as affected by irrigation rate. Irrigation rate was applied as percentage of crop evapotranspiration. Curve was fit by linear regression. Fall of 2010, Tifton, GA.

Seasonal volumetric soil water content (measured at 12- and 30-cm depth) as influenced by irrigation rate. Irrigation rate was applied as percentage of crop evapotranspiration. Line was fit by linear regression. Fall of 2010, Tifton, GA.

Effect of irrigation rate and soil depth on the concentration of nitrate-nitrogen in the soil (0 to 60 cm) in drip-irrigated eggplant grown on raised beds and plastic film mulch. Irrigation rate was applied as percentage of crop evapotranspiration. Line was fit by linear regression. Fall of 2010, Tifton, GA.

Cumulative number of fruit and fruit yields as affected by irrigation rate in drip-irrigated eggplant grown on raised beds and plastic film mulch. Irrigation rate was applied as percentage of crop evapotranspiration. Line was fit by linear regression. Fall of 2010, Tifton, GA.

Individual fruit weight as influenced by irrigation rate in drip-irrigated eggplant grown on raised beds and plastic film mulch. Irrigation rate was applied as percentage of crop evapotranspiration. Line was fit by linear regression. Fall of 2010, Tifton, GA.

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Eggplant ( Solanum melongena L.) Plant Growth and Fruit Yield as Affected by Drip Irrigation Rate

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Eggplant ( Solanum melongena L.) is an increasingly popular crop in the United States. In the southeastern United States, eggplant is often produced with high levels of irrigation water [above the rate of crop evapotranspiration (ETc)], resulting in water waste and nitrogen (N) leaching. The objective of this research was to assess the effects of irrigation rate on plant growth and fruit yield in eggplant. The study was conducted in Tifton, GA, in the fall of 2010 and 2011. Eggplant plants cv. Santana were grown on raised beds (1.8 m centers) covered with white plastic film mulch. There was a single drip tape along the center of the bed. The design was a randomized complete block with five treatments and four replications. Treatments consisted of irrigation rates based on ETc (33%, 67%, 100%, 133%, and 167% ETc). Plant growth, chlorophyll index (CI), and volumetric soil water content (SWC) were monitored over the season. In 2010, SWC (0–30 cm deep) increased and soil nitrate levels decreased with increasing irrigation rates. Foliar N and potassium (K), and CI decreased with increasing irrigation rate, probably due to a dilution effect. Stem diameter, leaf dry weight (DW), and vegetative top DW increased with increasing irrigation rate. Net photosynthesis and stomatal conductance ( g S ) were lowest at 33% ETc. Fruit number and fruit yields (marketable and total) were also lowest at 33% ETc and there were little yield differences among irrigation rates higher than 33% ETc. In 2011, irrigation rate had minor or no effect on SWC, plant growth of mature plants, leaf gas exchange, and fruit number and yield. The no treatment effect observed for eggplant in 2011 was likely because study was conducted in a low field that remained moist most of the time, nullifying the treatment effects. Results suggested that eggplant may tolerate mild water stress, since plants irrigated at 67% ETc produced fruit yields similar to those of plants irrigated at 100% ETc or higher rates. Thus, there is a potential to save water by reducing current irrigation rates without negatively impacting fruit yields.

Eggplant, also known as aubergine and brinjal, is widely grown and consumed in southern and southeast Asia and has increased in popularity in the United States as a specialty vegetable. In 2001, U.S. eggplant production was valued at $42.5 million, and Georgia, Florida, California, New Jersey, and New York were the top five producers. The U.S. Department of Agriculture has not collected complete domestic production statistics for eggplants since 2001. In 2012, farm gate value in the state of Georgia was $17 million ( CAED, 2013 ). Average eggplant yield in Florida is ≈30 t·ha −1 ( Ozores-Hampton, 2014 ).

Eggplant is in the Solanaceae family, as are tomato ( Solanum lycopersicon ) and pepper ( Capsicum annum ) and shares similar environmental and cultural requirements as those crops. However, in contrast to tomato and pepper, eggplant crop can tolerate greater levels of drought stress ( Behboudian, 1977 ). There are several studies on eggplant irrigation carried out in Asia, Africa, and Europe ( Aujla et al., 2007 ; Behboudian, 1977 ; Chartzoulakis and Drosos, 1995 ; Gaveh et al., 2011 ; Karam et al., 2011 ) showing that eggplant can be produced at moderate levels of drought stress without major impact on fruit yield.

In southeastern United States, eggplant is often produced with high levels of irrigation water (above the rate of ETc) and N fertilizer, resulting in water waste and N leaching. Excessive irrigation rate not only wastes water, but may also result in reduced yields in bell pepper ( Díaz-Pérez et al., 2004 ; Sezen et al., 2006 ) and tomato ( Locascio et al., 1989 ; Ngouajio et al., 2007 ). To our knowledge, there are no published studies in the United States on the effect of irrigation rate on the yield and plant growth of drip-irrigated eggplants. Irrigation studies, intended to optimize use of irrigation water, are necessary to enable the protection of water resources in the United States. Therefore, the objective of this research was to assess the effects of irrigation rate on plant growth and fruit yield in eggplant.

Study site.

The study was carried out at the Horticulture Farm, University of Georgia, Tifton, GA, during the fall of 2010 and 2011. The farm is located at an altitude of 108 m above mean sea level, 31°28′ N latitude and 83°31′ W longitude. The soil of the farm is a Tifton sandy loam (a fine loamy-siliceous, thermic Plinthic Kandiudults) with pH 6.5. Available water capacity is 18 to 36 mm in the top 30 cm of soil profile ( Calhoun, 1983 ). In 2010, field had a gentle sloping (slope ≈3%); in 2011, field had a nearly level slope. The distance between the 2010 and 2011 fields was ≈70 m.

Land preparation and planting.

Eggplant plants were grown on plastic film mulch on raised beds (6 × 0.76 m, formed on 1.8-m centers). Before laying mulch, the soil was fertilized with N, phosphorous (P), and K at 60, 26, and 50 kg·ha −1 , respectively, using 10–10–10 granular fertilizer. At the same time, plastic film mulch [white on black, low-density polyethylene with a slick surface texture, 1.52 m wide and 25 µm thick (RepelGro, ReflecTek Foils, Inc., Lake Zurich, IL)] was laid with a mulch-laying machine, drip irrigation tape [20.3 cm emitter spacing and a 8.3 mL·min −1 emitter flow (Ro-Drip, Roberts Irrigation Products, Inc., San Marcos, CA)] was placed 5 cm deep in the center of the bed.

Eggplant transplants were produced in a greenhouse using peat-based medium (Pro-Mix, Quakertown, PA) and polystyrene 200-cell (2.5 × 2.5 cm cell) trays. Six-week-old eggplant transplants were planted with a mechanical transplanter on 6 Aug. 2010 and 5 Aug. 2011 in one row per bed, with a 60 cm separation between plants. About 250 mL of starter fertilizer solution (555 mg·L −1 N; 821·mg·L −1 P; 0 mg·L −1 K) was applied directly to the base of each transplant. The length of the experimental plot was 6.1 m. Starting 3 weeks after transplanting, plants were fertilized weekly through the drip system with N and K. Fertilization rates of N and K after transplanting were 0.7, 1.0, 1.5, and 2 kg·ha −1 ·d −1 in week 5, week 6; week 7; and weeks 13–15, respectively. Total N–P–K applied in the season was 218 kg·ha −1 N, 30 kg·ha −1 P, and 181 kg·ha −1 K.

Experimental design and treatments.

The design was a randomized complete block with five treatments and four replications. Treatments consisted of irrigation rates based on ETc (33%, 67%, 100%, 133%, and 167% the rate of ETc). ETc was calculated by multiplying the reference evapotranspiration (ETo) by a crop coefficient (Kc), which is dependent on the crop stage of development. Available Kc values for eggplant were developed for bare soil (unmulched) production. These Kc values, however, are not recommended for crops under plasticulture systems since plastic mulches reduce soil evaporation and ETc ( Allen et al., 1998 ; Pereira et al., 2015 ; Simonne et al., 2006 ). The Kc values used in this study were modified relative to those proposed for bell pepper in Florida ( Simonne et al., 2006 ). The Kc values used were 0.25 (week 1 after transplanting), 0.40 (week 2), 0.55 (week 3), 0.70 (week 4), 0.85 (week 5), 1.0 (week 6–11), and 0.8 (week 12–14).

All treatments received equal volumes of irrigation water (88 and 49 mm in 2010 and 2011, respectively) during the crop establishment period (first 4 weeks after transplanting). Irrigation treatments were initiated on week 5. Water was applied when cumulative ETc was ≈12 mm, which corresponded to about every 2 to 3 d in mature plants (mean ETo was 5 to 6 mm·d −1 ). Thus, amounts of water per irrigation event were ≈4 mm (33% ETc), 8 mm (67% ETc), 12 mm (100% ETc), 16 mm (133% ETc), and 20 mm (167% ETc).

Soil water content.

Soil water content (volumetric) in the 0–12 cm of soil profile over the season was measured manually once every 2–3 d (three readings per experimental plot) with a portable time-domain reflectometry (TDR) sensor (CS-620; Campbell Scientific, Logan, UT). The two metallic 12-cm rods of the TDR sensor were inserted vertically within the row between two plants. Soil water content (volumetric) in the 0–30 cm of soil profile was periodically (every 10 min) monitored with TDR sensors (CS-610; Campbell Scientific) connected to a datalogger (CR-10X; Campbell Scientific). The moisture sensors had three metallic 30-cm rods and were inserted vertically within the row between two plants.

Soil nitrate.

Soil samples were taken from each plot at 0- to 20-cm, 20- to 40-cm, and 40- to 60-cm depths on 8 Nov. 2010. Samples were taken at least 0.5 m away from the borders of the plots and from the previous sampling holes. Samples were air-dried and analyzed for nitrate-nitrogen using standard QuickChem Methods (Lachat Quick-Chem 8000 FIA; Zellweger Analytics, Milwaukee, WI).

Plant growth.

Eggplant plant height and stem diameter were measured weekly in three mature plants per plot. Plant samples obtained at the end of the season were dried at 70 °C for several days until constant weight was obtained. Leaf, stem, and vegetative top (leaf + stem) DW of individual plants were determined.

Chlorophyll indices were determined twice a week over the season on six mature, well-exposed, and healthy leaves per plot using a chlorophyll meter (Chlorophyll Meter SPAD-502; Minolta Co., Ltd., Ramsey, NJ).

Leaf gas exchange and PSII efficiency.

Simultaneous measurements of leaf gas exchange (net photosynthesis, g S , transpiration, and internal CO 2 concentration), and fluorescence were determined as PSII efficiency were made with an infrared gas analyzer (LI-COR 6400 IRGA with an integrated 6400-40 leaf chamber fluorometer; LI-COR, Inc., Lincoln, NE). PSII efficiency is the fraction of absorbed PSII photons used in photochemistry and is measured with a light-adapted leaf. Water use efficiency (WUE) was calculated as the ratio between leaf net photosynthesis and leaf transpiration. Air flow rate was set at 300 µmol·m −2 ·s −1 on the reference side. The CO 2 concentration was set at 400 µmol·mol −1 with a CO 2 mixer and a CO 2 tank. Measurements were conducted in developed plants on clear days (photosynthetically active radiation ≈2000 µmol·m −2 ·s −1 ) at 1200–1500 hr Eastern Standard Time in 2010 (6 and 20 Oct. and 9 Nov.) and 2011 (5 Oct.), using two developed and fully exposed leaves per experimental plot.

Leaf mineral nutrients.

Leaf samples (20 fully developed leaves from new growth) from developed plants were dried at 70 °C for 2 d and analyzed for mineral nutrient concentration at the University of Georgia, Agricultural & Environmental Services Laboratories, Athens, GA.

Weather data (air temperature, ETo, and rainfall) were obtained from a nearby University of Georgia weather station (within 300 m).

The harvest lasted from 28 Sept. to 23 Nov. in 2010 and from 23 Sept. to 4 Nov. in 2011. Eggplant fruit were harvested twice per week at commercial stage. Harvested section consisted of 10 plants per plot. Fruit were graded according to U.S. Department of Agriculture standards ( USDA, 2013 ) as marketable or cull and number and weight of marketable and cull fruit were determined. Average fruit weight was derived mathematically from the total weight and the total number of fruits.

Irrigation water use efficiency.

Irrigation water use efficiency (IWUE) was calculated by dividing fruit weight (kg·ha −1 ) by irrigation water received by the crop (in mm) for each irrigation treatment.

Agronomic efficiency of nitrogen.

Agronomic efficiency of nitrogen was calculated by dividing total eggplant fresh fruit weight (kg·ha −1 ) by the amount of N (kg·ha −1 ) applied to the crop.

Fruit DW content and harvest index (HI).

Statistical analysis..

Data were analyzed using the General Linear Model and Regression Procedures from SAS (SAS version 9.3, SAS Institute Inc., Cary, NC). Data means were separated by Fisher’s protected least significant difference test at 95% confidence and response curves determined by orthogonal contrasts. Percentages were transformed to arcsin values before analysis. For clarity, nontransformed percentage means were used for presentation in tables and figures. Data from all years were pooled if no year × treatment interactions were found.

In 2010, average maximal, mean, and average minimum air temperature for the season were 28.8, 22.6, and 16.4 °C, respectively. Cumulative ETo and rainfall for the season were 370 and 184 mm, respectively. In 2011, average maximal, mean, and average minimum air temperature were 28.6, 22.5, and 16.4 °C, respectively. Cumulative ETo and rainfall for the season were 344 and 256 mm, respectively.

In 2010, vegetative top DW, leaf DW, stem DW, and stem diameter increased with increasing irrigation rate ( Fig. 1 ). Leaf weight ratio (LWR) [leaf biomass as a fraction of vegetative aboveground biomass (mean = 0.529)] decreased with increasing irrigation rate ( r 2 = 0.92; P ≤ 0.05) from LWR of 0.543 at 33% ETc to LWR of 0.493 at 167% ETc, which indicates that plants allocated less biomass to leaves as irrigation rate increased. Bell pepper leaves have reduced leaf thickness at low light and low water stress conditions ( Díaz-Pérez, 2013 ). In 2011, over the season, mean stem diameter was lowest at 33% ETc ( P < 0.05), although final stem diameter was unaffected by irrigation rate ( Table 1 ). Mean seasonal plant height increased with irrigation rate, ranging from 66 cm (33% ETc) to 93 cm (167% ETc); final plant height (4 Nov.) was unaffected by irrigation rate. Mature plant DW (mean = 1.70 kg) was also unaffected by irrigation rate. Growth differences during midseason but not at the end of the season were probably because of high evaporative demand conditions that impacted plant growth at low irrigation rates during midseason. Late in the season, when evaporative demand was reduced, the effect of irrigation rate on plant growth was less detectable. The no treatment effect observed for eggplant in 2011 was likely because study was conducted in a low field that remained moist most of the time, nullifying the treatment effects.

Citation: HortScience horts 50, 11; 10.21273/HORTSCI.50.11.1709

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Plant growth, leaf chlorophyll index (CI), and soil water content (SWC) as affected by irrigation rate in eggplant. Fall of 2011, Tifton, GA.

Reduced eggplant plant growth at irrigation rates below 100% ETo has been previously reported. Eggplant irrigated at 80% pan evaporation, every 8 d, and 70% pan evaporation, every 12 d, had reduction of 18% and 27% in plant height, and 13% and 21% in stem diameter, respectively ( Kirnak et al., 2002 ). In bell pepper exposed to different soil water levels by varying drip emitter spacing, plant height and canopy diameter increased with decreasing emitter spacing (i.e., with increased soil water levels) ( Madramootoo and Rigby, 1991 ).

In 2010, CIs decreased with increased irrigation rate ( P = 0.006), from 60.8 at 33% ETc to 59.0 at 167% ETc. In 2011, CI decreased from 55.8 at 33% ETc to 53.7 at 167% ETc ( Table 1 ). Decreased CI values with increased irrigation rates were likely due to dilution effect of nutrients, since plant growth was enhanced with increased irrigation rates. Decreased CI with increased irrigation rates may also be associated with increased nitrate leaching under high irrigation rates.

In 2010, the effect of irrigation rate on SWC varied with soil depth. At 0- to 30-cm depth, SWC increased with increasing irrigation rates ( Fig. 2 ), whereas at 0- to 12-cm depth SWC was unaffected by irrigation rate. Differences in soil moisture in the different soil depths indicate a higher soil water uptake by plants, because of greater presence of roots at 0–12 cm than at 0- to 30-cm depth; they also indicate that high rates of irrigation (>100% ETc) result in wasted water because much water at 0- to 30-cm depth was not taken up by the crop; and they suggest that soil moisture measurement at 0- to 30-cm depth was more sensitive to detect changes in soil moisture than measurement at 0- to 12-cm depth.

As in 2010, seasonal SWC at 0- to 12-cm depth was also similar among irrigation rates (mean = 13.4%) in 2011. In addition to the high presence of roots at 0- to 12-cm depth, SWC values were similar among treatments in 2011 probably because the study was conducted in a low field, with a nearly level slope, where soil was commonly moist throughout the season, likely due to lateral water movement from upper sections of the field. There was an impermeable clay layer 30- to 40-cm deep in the soil profile that probably allowed water to flow from upper to lower areas within the farm.

Leaf gas exchange.

In 2010, the effect of irrigation rate on leaf gas exchange varied by date ( Table 2 ). Net photosynthesis, g S , and photosynthetic WUE were unaffected by irrigation rate on 6 Oct. 2010. Lack of treatment differences on 6 Oct. was probably attributable to relatively low temperatures on day of measurement (mean temperature = 16.4 °C), resulting in low crop evaporative demand and low crop water stress. Net photosynthesis and g S were lowest at 33% ETc on 20 Oct. and 9 Nov. Water use efficiency was highest and PSII efficiency was lowest at 33% ETc on 20 Oct. The fact that gas exchange variables were not reduced at 67% ETc compared with higher irrigation rates suggests that plants at 67% ETc were likely unaffected by water stress. However, since gas exchange measurements were conducted only in mature plants, late in the season, when evaporative demand was reduced, it is possible that earlier in the season plants may have had experienced increased water stress at reduced irrigation rates, as suggested by the reduced plant growth at reduced irrigation rates. In 2011, leaf net photosynthesis (mean = 28.3 µmol·m −2 ·s −1 ), g S (mean = 0.248 mol·m −2 ·s −1 ), WUE (mean = 4.24 µmol·mmol −1 ), and PSII (mean = 0.189 µmol·mmol −1 ) were unaffected by irrigation rate. Air maximal and minimal temperature on the day of measurement were 27.5 and 11.0 °C, respectively. Lack of differences in gas exchange are consistent with the lack of differences in plant growth among irrigation rates observed in 2011.

Leaf gas exchange and fluorescence as affected by irrigation rate and date in eggplant. Fall of 2010, Tifton, GA.

Irrigation at 33% ETc was probably insufficient to satisfy eggplant water requirements, as suggested by the reduced leaf gas exchange values ( Table 2 ). Reduced irrigation rates can result in decreased gas exchange in solanaceous crops. Transpiration, leaf g S , and leaf net photosynthesis in eggplant were reduced with water stress and effects varied depending on stress severity and duration ( Sarker et al., 2005 ). In habanero pepper ( Capsicum chinense Jacq.), there was reduced g S and net photosynthesis with increased time between irrigations ( Jaimez et al., 1999 ).

Soil nitrate concentration decreased with increasing irrigation rate ( P = 0.002) and soil depth ( P = 0.003), indicating that nitrate leaching to the deepest parts of the soil was enhanced with increased irrigation rates ( Fig. 3 ). Decreased soil nitrate concentration may also be due to high N uptake by the crop, as suggested by augmented vegetative growth with increasing irrigation rate. Nitrate present at 40–60 depth is usually lost as it is not recovered by plants’ roots. Decreased nitrate in 40- to 60-cm zone is thus solely due to leaching.

Foliar mineral nutrient concentrations and CI.

In 2010, foliar N and K concentrations decreased and P increased with increasing irrigation rate ( Table 3 ). Other foliar nutrients concentrations were unaffected by irrigation rate. Nitrogen, K, and CI decreased with irrigation rate, possibly as a result of a dilution effect associated with increased aboveground plant growth. In addition, at high irrigation rates plants likely had reduced access to soil N due to increased nitrate leaching. Plant water stress in eggplant can reduce foliar N, P, and K concentrations compared with well-irrigated plants ( Kirnak et al., 2002 ). In the present study, however, only foliar P was reduced at low irrigation rate.

Foliar mineral nutrient concentrations in eggplant as affected by several irrigation rates. Fall of 2010, Tifton, GA. z

Chlorophyll indices have been used as indirect estimators of chlorophyll and leaf N concentrations ( Liu et al., 2006 ). Crop drought stress may influence leaf morphology (e.g., increased specific leaf weight) in plants ( Larcher, 1995 ); these variations in leaf morphology may also influence CI, making difficult to use CI to estimate leaf N ( Díaz-Pérez, 2013 ). In our study, CI values increased with increasing leaf N ( R 2 = 0.921; P = 0.001), supporting the use of chlorophyll meter to estimate leaf N.

In 2010, fruit number and fruit yields (marketable and total) were lowest at 33% ETc and there were little yield differences among irrigation rates higher than 33% ETc ( Fig. 4 ). Individual fruit weight was also reduced at 33% ETc ( Fig. 5 ). There was a higher correlation between fruit number and fruit yield ( R 2 = 0.94; P < 0.0001) than between individual fruit weight and fruit yield ( R 2 = 0.15; P = 0.027), suggesting that marketable yield was determined more by fruit number than individual fruit weight. In greenhouse-grown eggplant, soil water deficit decreased fruit number but not fruit size ( Chartzoulakis and Drosos, 1995 ). In a study with different levels of irrigation and N fertilizer, eggplant fruit yield was more related with fruit number than with fruit size ( Aujla et al., 2007 ). In another study, soil water deficits also reduced eggplant fruit size, but the effect of drought stress on fruit number was not evaluated ( Kirnak et al., 2002 ). In 2011, irrigation rate had no effect on the number or yields of marketable, cull, and total fruit, or on individual fruit weight ( Table 4 ). There were no significant interactions between harvest dates and irrigation rates. There was also a higher correlation between fruit number and fruit yield ( R 2 = 0.92; P < 0.0001) than between individual fruit weight and fruit yield ( R 2 = 0.185; P = 0.001). Results suggest that eggplant may tolerate moderate water stress, since plants irrigated at 67% ETc produced fruit yields similar to those of plants irrigated at 100% ETc or higher rates. Thus, there is a potential to reduce irrigation rates below 100% ETc without negatively impacting fruit yields.

Fruit yield of eggplant as affected by irrigation rate. Fall of 2011, Tifton, GA.

Irrigation water use efficiency and agronomic efficiency of nitrogen.

Plants received more irrigation water in 2010 than in 2011 as a result of reduced rainfall in 2010 ( Table 5 ). In both years, IWUE decreased with increasing irrigation rate. IWUE was greatly reduced and there were significant effects of irrigation rates on several variables in 2010, but not in 2011. Increased IWUE and increased SWC in 2011 (mean = 13.4% at 0- to 12-cm depth) relative to SWC in 2010 (mean = 7.5% at 0- to 12-cm depth) are probably associated with increased contribution of soil water from rainfall and drainage water from upper areas of the field; in 2011, field used was low and nearly flat.

Irrigation, cumulative rainfall, IWUE, and AEN of eggplant crop grown on plastic film mulch. Fall of 2010 and 2011, Tifton, GA.

Although there were differences in leaf N among irrigation treatments, fruit yield was likely more related to irrigation rate than to leaf N. Total yield showed a quadratic relationship with leaf N ( R 2 = 0.185; P = 0.013); total yield was unaffected by leaf N below 5.1% and was lowest at the highest leaf N (5.3%) occurred at the lowest irrigation rate (33% ETc).

Agronomic efficiency of N increased with irrigation rate in 2010 likely as a result of increased fruit yield associated with improved plant water status; AEN was unaffected by irrigation rate in 2011. AEN values in this study (range 92 to 187 kg·kg −1 N) were lower compared with values of other studies on eggplant (range = 324 to 859 kg·kg −1 N) ( Aujla et al., 2007 ), probably because the harvest period in this study was reduced. Low AEN values may also mean that eggplant crop in this study made inefficient use of N fertilizer, probably in part due to overfertilization. Aujla et al. (2007) reported that irrigation rate and N fertilization rate interacted in drip-irrigated eggplants; they also found that irrigation at 75% pan evaporation and 120 kg·ha −1 N produced the greatest yields, and that AEN increased with increased N fertilization rate.

Fruit DW content and HI.

In year 2010, fruit DW content (mean = 6.2%) was unaffected by irrigation rate. In a study under semiarid conditions, soluble DW or soluble solids in eggplant decreased with increased irrigation rates ( Kirnak et al., 2002 ). In greenhouse-grown eggplant, increased irrigation rates also decreased fruit DW content ( Chartzoulakis and Drosos, 1995 ).

Harvest index was unaffected by irrigation rate (mean HI = 0.32). These data suggest that eggplant is more tolerant to drought than other solanaceous crops ( Behboudian, 1977 ). Our measurements of HI did not include root biomass. However, under water stress, eggplants possibly allocated increased amounts of assimilates for root growth as occurs in other plants ( Larcher, 1995 ). In habanero pepper, an irrigation rate of 20% of available water produced reduced values of HI ( Quintal Ortiz et al., 2012 ). In tomato, there was no difference in total dry biomass and HI between the control and a partial irrigation treatment, but total dry biomass and HI significantly decreased under regulated deficit irrigation ( Lei et al., 2009 ); moderate water stress–induced osmotic regulation under partial root drying conditions, leading to normal water status and the same level of biomass. Eggplant in our study was also able to maintain high fruit yields at moderate levels of water stress, suggesting that, as tomato, eggplant is also able to develop mechanisms to deal with water stress such as osmoregulation.

In conclusion, the results from this research indicate that eggplant may tolerate moderate water stress, since plants irrigated at 67% ETc had no detrimental effects on plant growth and leaf gas exchange and produced fruit yields similar to those of plants irrigated at 100% ETc. Thus, there is a potential to reduce current irrigation rates without negatively impacting fruit yields or quality.

Literature Cited

Allen, R.G. , Pereira, L.S. , Raes, D. & Smith, M. 1998 Crop evapotranspiration: Guidelines for computing crop water requirements. Food and Agriculture Organization of the United Nations, Rome

Aujla, M.S. , Thind, H.S. & Buttar, G.S. 2007 Fruit yield and water use efficiency of eggplant ( Solanum melongema L.) as influenced by different quantities of nitrogen and water applied through drip and furrow irrigation Sci. Hort. 112 142 148

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Behboudian, M.H. 1977 Responses of eggplant to drought. I. Plant water balance Sci. Hort. 7 303 310

CAED 2013 2012 Georgia farm gate value report. CAES, Univ. of Georgia, Athens, GA

Calhoun, J.W. 1983 Soil survey of Tift County, Georgia. United States Department of Agriculture, Soil Conservation Service, University of Georgia, GA

Chartzoulakis, K. & Drosos, N. 1995 Water use and yield of greenhouse grown eggplant under drip irrigation Agr. Water Mgt. 28 113 120

Díaz-Pérez, J.C. 2013 Bell pepper ( Capsicum annum L.) crop as affected by shade level: Microenvironment, plant growth, leaf gas exchange, and leaf mineral nutrient concentration HortScience 48 175 182

Díaz-Pérez, J.C. , Granberry, D. , Seebold, K. , Giddings, D. & Bertrand, D. 2004 Irrigation levels affect plant growth and fruit yield of drip-irrigated bell pepper HortScience 39 748

Gaveh, E.A. , Timpo, G.M. , Agodzo, S.K. & Shin, D.H. 2011 Effect of Irrigation, transplant age and season on growth, yield and irrigation water use efficiency of the African eggplant J. Hort. Environ. Biotechnol. 52 13 28

Jaimez, R.E. , Rada, F. & Garcia-Nunez, C. 1999 The effect of irrigation frequency on water and carbon relations in three cultivars of sweet pepper ( Capsicum chinense Jacq), in a tropical semiarid region Sci. Hort. 81 301 308

Karam, F. , Saliba, R. , Skaf, S. , Breidy, J. , Rouphael, Y. & Balendonck, J. 2011 Yield and water use of eggplants ( Solanum melongena L.) under full and deficit irrigation regimes Agr. Water Mgt. 98 1307 1316

Kirnak, H. , Tas, I. , Kaya, C. & Higgs, D. 2002 Effects of deficit irrigation on growth, yield, and fruit quality of eggplant under semi-arid conditions Austral. J. Agr. Res. 53 1367 1373

Larcher, W. 1995 Physiological plant ecology: Ecophysiological and stress physiology of functional groups. Springer, Berlin, Germany

Lei, S. , Yunzhou, Q. , Fengchao, J. , Changhai, S. , Chao, Y. , Yuxin, L. , Mengyu, L. & Baodi, D. 2009 Physiological mechanism contributing to efficient use of water in field tomato under different irrigation Plant Soil Environ. 55 128 133

Liu, Y.J. , Tong, Y.P. , Zhu, Y.G. , Ding, H. & Smith, E.A. 2006 Leaf chlorophyll readings as an indicator for spinach yield and nutritional quality with different nitrogen fertilizer applications J. Plant Nutr. 29 1207 1217

Locascio, S.J. , Olson, S.M. & Rhoads, F.M. 1989 Water quantity and time of N and K application for trickle-irrigated tomatoes J. Amer. Soc. Hort. Sci. 114 265 268

Madramootoo, C.A. & Rigby, M. 1991 Effects of trickle irrigation on the growth and sunscald of bell peppers ( Capsicum annuum L.) in southern Quebec Agr. Water Mgt. 19 181 189

Ngouajio, M. , Wang, G.Y. & Goldy, R. 2007 Withholding of drip irrigation between transplanting and flowering increases the yield of field-grown tomato under plastic mulch Agr. Water Mgt. 87 285 291

Ozores-Hampton, M. 2014 Conventional and specialty eggplant varieties in Florida. Horticultural Sciences Department, Univ. of Florida/Institute of Food and Agricultural Sciences. Document HS1243. 12 June 2015. < http://edis.ifas.ufl.edu/hs1243 >.

Pereira, L.S. , Allen, R.G. , Smith, M. & Raes, D. 2015 Crop evapotranspiration estimation with FAO56: Past and future Agr. Water Mgt. 147 4 20

Quintal Ortiz, W.C. , Perez-Gutierrez, A. , Latournerie Moreno, L. , May-Lara, C. , Ruiz Sanchez, E. & Martinez Chacon, A.J. 2012 Water use, water potential, and yield of habanero pepper ( Capsicum chinense Jacq.) Rev. Fitotec. Mex. 35 155 160

Sarker, B.C. , Hara, M. & Uemura, M. 2005 Proline synthesis, physiological responses and biomass yield of eggplants during and after repetitive soil moisture stress Sci. Hort. 103 387 402

Sezen, S.M. , Yazar, A. & Eker, S. 2006 Effect of drip irrigation regimes on yield and quality of field grown bell pepper Agr. Water Mgt. 81 115 131

Simonne, E.H. , Dukes, M.D. , Hochmuth, R.C. , Studstill, D.W. , Avezou, G. & Jarry, D. 2006 Scheduling drip irrigation for bell pepper grown with plasticulture J. Plant Nutr. 29 1729 1739

USDA 2013 United States standards for grades of eggplant. United States Department of Agriculture

Contributor Notes

Financial support was provided by the Georgia Agricultural Experiment Stations.

We thank John Silvoy, Jesús Bautista, and Nélida Bautista for their invaluable technical support. We also thank Peter Germishuizen from Lewis Taylor Farms, Ty Ty, GA, for donation of eggplant transplants. We appreciate the thorough review of the manuscript by Pat Conner, Tim Coolong, Erick Smith, and the anonymous reviewers.

Mention of trade names in this publication does not imply endorsement by the University of Georgia of products named, nor criticism of similar ones not mentioned. The cost of publishing this paper was defrayed in part by payment of page charges. Under postal regulations, this paper therefore must hereby be marked advertisement solely to indicate this fact.

1 Corresponding author. E-mail: [email protected] .

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Biochemical composition of eggplant fruits: a review.

1. Introduction

2. material and methods, 3. proteins in eggplant, 4. vitamins in eggplant, 5. minerals in eggplant, 6. carbohydrates in eggplant, 7. phenolics in eggplant, 8. phenolic acids in eggplant, 9. anthocyanins in eggplant, 10. flavonoids in eggplant, 11. dry matter content of eggplant, 12. conclusions and future directions, author contributions, institutional review board statement, informed consent statement, data availability statement, acknowledgments, conflicts of interest.

• Rotino, G.L.; Sala, T.; Toppino, L. Eggplant. In Alien Gene Transfer in Crop Plants, Volume 2 ; Springer: Berlin/Heidelberg, Germany, 2014; pp. 381–409. [ Google Scholar ]
• Mwinuka, P.R.; Mbilinyi, B.P.; Mbungu, W.B.; Mourice, S.K.; Mahoo, H.F.; Schmitter, P. Optimizing water and nitrogen application for neglected horticultural species in tropical sub-humid climate areas: A case of African eggplant ( Solanum aethiopicum L.). Sci. Hortic. 2021 , 276 , 109756. [ Google Scholar ] [ CrossRef ]
• Braga, P.C.; Scalzo, R.L.; Sasso, M.D.; Lattuada, N.; Greco, V.; Fibiani, M. Characterization and antioxidant activity of semi-purified extracts and pure delphinidin-glycosides from eggplant peel ( Solanum melongena L.). J. Funct. Foods 2016 , 20 , 411–421. [ Google Scholar ] [ CrossRef ]
• Blando, F.; Calabriso, N.; Berland, H.; Maiorano, G.; Gerardi, C.; Carluccio, M.A.; Andersen, Ø.M. Radical scavenging and anti-inflammatory activities of representative anthocyanin groupings from pigment-rich fruits and vegetables. Int. J. Mol. Sci. 2018 , 19 , 169. [ Google Scholar ] [ CrossRef ] [ Green Version ]
• Niño-Medina, G.; Urías-Orona, V.; Muy-Rangel, M.D.; Heredia, J.B. Structure and content of phenolics in eggplant ( Solanum melongena )—A review. S. Afr. J. Bot. 2017 , 111 , 161–169. [ Google Scholar ] [ CrossRef ]
• Kaushik, P.; Saini, D.K. Sequence analysis and homology modelling of SmHQT protein, a key player in chlorogenic acid pathway of eggplant. bioRxiv 2019 , 599282. [ Google Scholar ] [ CrossRef ]
• Cárdenas, P.D.; Sonawane, P.; Heinig, U.; Bocobza, S.; Burdman, S.; Aharoni, A. The bitter side of the nightshades: Genomics drives discovery in Solanaceae steroidal alkaloid metabolism. Phytochemistry 2015 , 113 , 24–32. [ Google Scholar ] [ CrossRef ]
• Toppino, L.; Barchi, L.; Scalzo, R.L.; Palazzolo, E.; Francese, G.; Fibiani, M.; D’Alessandro, A.; Papa, V.; Laudicina, V.A.; Sabatino, L.; et al. Mapping quantitative trait loci affecting biochemical and morphological fruit properties in eggplant ( Solanum melongena L.). Front. Plant Sci. 2016 , 7 , 256. [ Google Scholar ] [ CrossRef ] [ PubMed ] [ Green Version ]
• Zhang, Y.-J.; Gan, R.-Y.; Li, S.; Zhou, Y.; Li, A.-N.; Xu, D.-P.; Li, H.-B. Antioxidant phytochemicals for the prevention and treatment of chronic diseases. Molecules 2015 , 20 , 21138–21156. [ Google Scholar ] [ PubMed ]
• Kaushik, P.; Gramazio, P.; Vilanova, S.; Raigón, M.D.; Prohens, J.; Plazas, M. Phenolics Content, Fruit Flesh Colour and Browning in Cultivated Eggplant, Wild Relatives and Interspecific Hybrids and Implications for Fruit Quality Breeding. Food Research International 2017 , 102 , 392–401. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Yadav, V.K.; Singh, R.; Jha, R.K.; Kaushik, P. Biochemical variability of eggplant peel among Indian cultivars. Indian J. Biochem. Biophys. (IJBB) 2020 , 57 , 634–637. [ Google Scholar ]
• Singh, S.; Devi, M.B. Vegetables as a potential source of nutraceuticals and phytochemicals: A review. Int. J. Med. Pharm. Sci. 2015 , 5 , 1–14. [ Google Scholar ]
• Gürbüz, N.; Uluişik, S.; Frary, A.; Frary, A.; Doğanlar, S. Health benefits and bioactive compounds of eggplant. Food Chem. 2018 , 268 , 602–610. [ Google Scholar ] [ CrossRef ]
• Valenzuela, J.L.; Manzano, S.; Palma, F.; Carvajal, F.; Garrido, D.; Jamilena, M. Oxidative stress associated with chilling injury in immature fruit: Postharvest technological and biotechnological solutions. Int. J. Mol. Sci. 2017 , 18 , 1467. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Rodriguez-Jimenez, J.R.; Amaya-Guerra, C.A.; Baez-Gonzalez, J.G.; Aguilera-Gonzalez, C.; Urias-Orona, V.; Nino-Medina, G. Physicochemical, functional, and nutraceutical properties of eggplant flours obtained by different drying methods. Molecules 2018 , 23 , 3210. [ Google Scholar ] [ CrossRef ] [ PubMed ] [ Green Version ]
• Scorsatto, M.; Pimentel, A.D.C.; Da Silva, A.J.R.; Sabally, K.; Rosa, G.; De Oliveira, G.M.M. Assessment of bioactive compounds, physicochemical composition, and in vitro antioxidant activity of eggplant flour. Int. J. Cardiovasc. Sci. 2017 , 30 , 235–242. [ Google Scholar ] [ CrossRef ]
• Samtiya, M.; Aluko, R.E.; Dhewa, T.; Moreno-Rojas, J.M. Potential Health Benefits of Plant Food-Derived Bioactive Components: An Overview. Foods 2021 , 10 , 839. [ Google Scholar ] [ CrossRef ]
• Guillermo, N.M.; Dolores, M.R.; Gardea-Bejar, A.; Gonzalez-Aguilar, G.; Heredia, B.; Manuel, B.S.; Siller-Cepeda, J.; De La Rocha, R.V. Nutritional and nutraceutical components of commercial eggplant types grown in Sinaloa, Mexico. Not. Bot. Horti Agrobot. Cluj-Napoca 2014 , 42 , 538–544. [ Google Scholar ]
• Siasos, G.; Tousoulis, D.; Tsigkou, V.; Kokkou, E.; Oikonomou, E.; Vavuranakis, M.; Basdra, E.; Papavassiliou, A.; Stefanadis, C. Flavonoids in atherosclerosis: An overview of their mechanisms of action. Curr. Med. Chem. 2013 , 20 , 2641–2660. [ Google Scholar ] [ CrossRef ]
• Naeem, M.Y.; Ugur, S. Nutritional Content and Health Benefits of Eggplant. Turk. J. Agric. Food Sci. Technol. 2019 , 7 , 31–36. [ Google Scholar ]
• Ekweogu, C.N.; Ude, V.C.; Nwankpa, P.; Emmanuel, O.; Ugbogu, E.A. Ameliorative effect of aqueous leaf extract of Solanum aethiopicum on phenylhydrazine-induced anaemia and toxicity in rats. Toxicol. Res. 2020 , 36 , 227–238. [ Google Scholar ] [ CrossRef ]
• Friedman, M. Chemistry and anticarcinogenic mechanisms of glycoalkaloids produced by eggplants, potatoes, and tomatoes. J. Agric. Food Chem. 2015 , 63 , 3323–3337. [ Google Scholar ] [ CrossRef ]
• Seraj, H.; Afshari, F.; Hashemi, Z.S.; Timajchi, M.; Olamafar, E.; Ghotbi, L. Effect of Eggplant Skin in the Process of Apoptosis in Cancer Cells. STEM Fellowsh. J. 2017 , 3 , 7–14. [ Google Scholar ] [ CrossRef ] [ Green Version ]
• S Panickar, K.; Jang, S. Dietary and plant polyphenols exert neuroprotective effects and improve cognitive function in cerebral ischemia. Recent Pat. Food Nutr. Agric. 2013 , 5 , 128–143. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Gramazio, P.; Yan, H.; Hasing, T.; Vilanova, S.; Prohens, J.; Bombarely, A. Whole-genome resequencing of seven eggplant ( Solanum melongena ) and one wild relative ( S. incanum ) accessions provides new insights and breeding tools for eggplant enhancement. Front. Plant Sci. 2019 , 10 , 1220. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Kaushik, P. Characterization of Cultivated Eggplant and its Wild Relatives Based on Important Fruit Biochemical Traits. Pak. J. Biol. Sci. PJBS 2020 , 23 , 1220–1226. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Kaushik, P. Line× Tester analysis for morphological and fruit biochemical traits in eggplant ( Solanum melongena L.) using wild relatives as testers. Agronomy 2019 , 9 , 185. [ Google Scholar ] [ CrossRef ] [ Green Version ]
• Fonseka, R.M.; Fonseka, H.H.D.; Abhyapala, K. Crop Wild Relatives: An Underutilized Genetic Resource for Improving Agricultural Productivity and Food Security. In Agricultural Research for Sustainable Food Systems in Sri Lanka ; Springer: Berlin/Heidelberg, Germany, 2020; pp. 11–38. [ Google Scholar ]
• Plazas, M.; Prohens, J.; Cuñat, A.N.; Vilanova, S.; Gramazio, P.; Herraiz, F.J.; Andújar, I. Reducing capacity, chlorogenic acid content and biological activity in a collection of scarlet ( Solanum aethiopicum ) and gboma ( S. macrocarpon ) eggplants. Int. J. Mol. Sci. 2014 , 15 , 17221–17241. [ Google Scholar ] [ CrossRef ] [ Green Version ]
• Shamseer, L.; Moher, D.; Clarke, M.; Ghersi, D.; Liberati, A.; Petticrew, M.; Shekelle, P.; Stewart, L.A. Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-P) 2015: Elaboration and Explanation. BMJ 2015 , 349 , g7647. [ Google Scholar ] [ CrossRef ] [ Green Version ]
• Raigon, M.D.; Rodriguez-Burruezo, A.; Prohens, J. Effects of organic and conventional cultivation methods on composition of eggplant fruits. J. Agric. Food Chem. 2010 , 58 , 6833–6840. [ Google Scholar ] [ CrossRef ]
• Raigón, M.D.; Prohens, J.; Muñoz-Falcón, J.E.; Nuez, F. Comparison of eggplant landraces and commercial varieties for fruit content of phenolics, minerals, dry matter and protein. J. Food Compos. Anal. 2008 , 21 , 370–376. [ Google Scholar ] [ CrossRef ]
• Kandoliya, U.K.; Bajaniya, V.K.; Bhadja, N.K.; Bodar, N.P.; Golakiya, B.A. Antioxidant and nutritional components of eggplant ( Solanum melongena L.) fruit grown in Saurastra region. Int. J. Curr. Microbiol. Appl. Sci. 2015 , 4 , 806–813. [ Google Scholar ]
• Das, S.; Raychaudhuri, U.; Falchi, M.; Bertelli, A.; Braga, P.C.; Das, D.K. Cardioprotective properties of raw and cooked eggplant ( Solanum melongena L). Food Funct. 2011 , 2 , 395–399. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Al Nachar, K. Investigation and Measurement of Some Mineral and Vitamins in Eggplant Fruit Calyx, and the Possibility of Being Used As Food Supplements and Alternative Medicine. J. Food Nutr. 2019 , 5 , 1–10. [ Google Scholar ]
• Edeke, A.; Uchendu, N.; Omeje, K.; Odiba, A.S. Nutritional and Pharmacological Potentials of Solanum melongena and Solanum aethiopicum Fruits. J. Phytopharm. 2021 , 10 , 61–67. [ Google Scholar ] [ CrossRef ]
• Evans, M.; Rumberger, J.A.; Azumano, I.; Napolitano, J.J.; Citrolo, D.; Kamiya, T. Pantethine, a Derivative of Vitamin B5, Favorably Alters Total, LDL and Non-HDL Cholesterol in Low to Moderate Cardiovascular Risk Subjects Eligible for Statin Therapy: A Triple-Blinded Placebo and Diet-Controlled Investigation. Vasc. Health Risk Manag. 2014 , 10 , 89–100. [ Google Scholar ] [ CrossRef ] [ Green Version ]
• Shabetya, O.N.; Kotsareva, N.V.; Nasser, A.M.; Katskaya, A.G.; Al-Maidi, A.A. Biochemical Composition of Eggplant and Its Change during Storage. Plant Arch. 2020 , 20 , 385–388. [ Google Scholar ]
• Arivalagan, M.; Gangopadhyay, K.; Kumar, G.; Bhardwaj, R.; Prasad, T.; Sarkar, S.; Roy, A. Variability in mineral composition of Indian eggplant ( Solanum melongena L.) genotypes. J. Food Compos. Anal. 2012 , 26 , 173–176. [ Google Scholar ] [ CrossRef ]
• Davidson, G.I.; Monulu, A.G. Vitamins and Minerals Composition of Eggplant (Solanum macrocarpon) and ‘Ukazi’(Gnetum africanum) leaves as affected by boiling and steaming. J. Sci. Res. Rep. 2018 , 21 , 1–8. [ Google Scholar ] [ CrossRef ]
• San José, R.; Plazas, M.; Sánchez-Mata, M.C.; Cámara, M.; Prohens, J. Diversity in composition of scarlet ( S. aethiopicum ) and gboma ( S. macrocarpon ) eggplants and of interspecific hybrids between S. aethiopicum and common eggplant ( S. melongena ). J. Food Compos. Anal. 2016 , 45 , 130–140. [ Google Scholar ] [ CrossRef ]
• Boo, H.; Kim, H.; Lee, H. Changes in sugar content and sucrose synthase enzymes during fruit growth in eggplant ( Solanum melongena L.) grown on different polyethylene mulches. HortScience 2010 , 45 , 775–777. [ Google Scholar ] [ CrossRef ] [ Green Version ]
• Meenakshi, S.; Kamal, D.; Malhotra, S.P. Carbohydrate metabolism in tomato ( Lycopersicon esculentum L. Mill) fruits during ripening. J. Food Sci. Technol. (Mysore) 2000 , 37 , 222–226. [ Google Scholar ]
• San José, R.; Sánchez, M.C.; Cámara, M.M.; Prohens, J. Composition of eggplant cultivars of the O ccidental type and implications for the improvement of nutritional and functional quality. Int. J. Food Sci. Technol. 2013 , 48 , 2490–2499. [ Google Scholar ] [ CrossRef ]
• Okmen, B.; Sigva, H.O.; Mutlu, S.; Doganlar, S.; Yemenicioglu, A.; Frary, A. Total antioxidant activity and total phenolic contents in different Turkish eggplant ( Solanum melongena L.) cultivars. Int. J. Food Prop. 2009 , 12 , 616–624. [ Google Scholar ] [ CrossRef ] [ Green Version ]
• Ninfali, P.; Mea, G.; Giorgini, S.; Rocchi, M.; Bacchiocca, M. Antioxidant capacity of vegetables, spices and dressings relevant to nutrition. Br. J. Nutr. 2005 , 93 , 257–266. [ Google Scholar ] [ CrossRef ] [ Green Version ]
• Hanson, P.M.; Yang, R.-Y.; Tsou, S.C.; Ledesma, D.; Engle, L.; Lee, T.-C. Diversity in eggplant ( Solanum melongena ) for superoxide scavenging activity, total phenolics, and ascorbic acid. J. Food Compos. Anal. 2006 , 19 , 594–600. [ Google Scholar ] [ CrossRef ]
• Kaur, C.; Nagal, S.; Nishad, J.; Kumar, R. Evaluating eggplant ( Solanum melongena L.) genotypes for bioactive properties: A chemometric approach. Food Res. Int. 2014 , 60 , 205–211. [ Google Scholar ] [ CrossRef ]
• Plazas, M.; Andújar, I.; Vilanova, S.; Hurtado, M.; Gramazio, P.; Herráiz, F.J.; Prohens, J. Breeding for chlorogenic acid content in eggplant: Interest and prospects. Not. Bot. Horti Agrobot. Cluj-Napoca 2013 , 41 , 26–35. [ Google Scholar ] [ CrossRef ] [ Green Version ]
• Whitaker, B.D.; Stommel, J.R. Distribution of hydroxycinnamic acid conjugates in fruit of commercial eggplant ( Solanum melongena L.) cultivars. J. Agric. Food Chem. 2003 , 51 , 3448–3454. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Plazas, M.; López-Gresa, M.P.; Vilanova, S.; Torres, C.; Hurtado, M.; Gramazio, P.; Andújar, I.; Herráiz, F.J.; Bellés, J.M.; Prohens, J. Diversity and relationships in key traits for functional and apparent quality in a collection of eggplant: Fruit phenolics content, antioxidant activity, polyphenol oxidase activity, and browning. J. Agric. Food Chem. 2013 , 61 , 8871–8879. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Zaro, M.J.; Keunchkarian, S.; Chaves, A.R.; Vicente, A.R.; Concellón, A. Changes in bioactive compounds and response to postharvest storage conditions in purple eggplants as affected by fruit developmental stage. Postharvest Biol. Technol. 2014 , 96 , 110–117. [ Google Scholar ] [ CrossRef ]
• Luthria, D.L. A simplified UV spectral scan method for the estimation of phenolic acids and antioxidant capacity in eggplant pulp extracts. J. Funct. Foods 2012 , 4 , 238–242. [ Google Scholar ] [ CrossRef ]
• Yousuf, B.; Gul, K.; Wani, A.A.; Singh, P. Health benefits of anthocyanins and their encapsulation for potential use in food systems: A review. Crit. Rev. Food Sci. Nutr. 2016 , 56 , 2223–2230. [ Google Scholar ] [ CrossRef ]
• Mazza, G.J. Anthocyanins and Heart Health. Ann. Ist. Super. Sanita 2007 , 43 , 369–374. [ Google Scholar ]
• Lin, B.-W.; Gong, C.-C.; Song, H.-F.; Cui, Y.-Y. Effects of Anthocyanins on the Prevention and Treatment of Cancer. Br. J. Pharmacol. 2017 , 174 , 1226–1243. [ Google Scholar ] [ CrossRef ] [ Green Version ]
• Casati, L.; Pagani, F.; Braga, P.C.; Scalzo, R.L.; Sibilia, V. Nasunin, a new player in the field of osteoblast protection against oxidative stress. J. Funct. Foods 2016 , 23 , 474–484. [ Google Scholar ] [ CrossRef ]
• Seeram, N.P.; Bourquin, L.D.; Nair, M.G. Degradation products of cyanidin glycosides from tart cherries and their bioactivities. J. Agric. Food Chem. 2001 , 49 , 4924–4929. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Ghosh, D.; Konishi, T. Anthocyanins and anthocyanin-rich extracts: Role in diabetes and eye function. Asia Pac. J. Clin. Nutr. 2007 , 16 , 200–208. [ Google Scholar ] [ PubMed ]
• Nisha, P.; Nazar, P.A.; Jayamurthy, P. A comparative study on antioxidant activities of different varieties of Solanum melongena. Food Chem. Toxicol. 2009 , 47 , 2640–2644. [ Google Scholar ] [ CrossRef ]
• Boulekbache-Makhlouf, L.; Medouni, L.; Medouni-Adrar, S.; Arkoub, L.; Madani, K. Effect of solvents extraction on phenolic content and antioxidant activity of the byproduct of eggplant. Ind. Crop. Prod. 2013 , 49 , 668–674. [ Google Scholar ] [ CrossRef ]
• Dranca, F.; Oroian, M. Optimization of ultrasound-assisted extraction of total monomeric anthocyanin (TMA) and total phenolic content (TPC) from eggplant ( Solanum melongena L.) peel. Ultrason. Sonochem. 2016 , 31 , 637–646. [ Google Scholar ] [ CrossRef ]
• Scalzo, R.L.; Fibiani, M.; Francese, G.; D’Alessandro, A.; Rotino, G.L.; Conte, P.; Mennella, G. Cooking influence on physico-chemical fruit characteristics of eggplant ( Solanum melongena L.). Food Chem. 2016 , 194 , 835–842. [ Google Scholar ] [ CrossRef ] [ PubMed ] [ Green Version ]
• Wu, X.; Beecher, G.R.; Holden, J.M.; Haytowitz, D.B.; Gebhardt, A.S.E.; Prior, R.L. Concentrations of anthocyanins in common foods in the United States and estimation of normal consumption. J. Agric. Food Chem. 2006 , 54 , 4069–4075. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Bor, J.-Y.; Chen, H.-Y.; Yen, G. Evaluation of antioxidant activity and inhibitory effect on nitric oxide production of some common vegetables. J. Agric. Food Chem. 2006 , 54 , 1680–1686. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Nayanathara, A.R.; Mathews, A.; Aalolam, K.P.; Reshma, J.K. Evaluation of total phenol, flavonoid and anthocyanin content in different varieties of eggplant. Emergent Life Sci. Res. 2016 , 2 , 63–65. [ Google Scholar ]
• Akanitapichat, P.; Phraibung, K.; Nuchklang, K.; Prompitakkul, S. Antioxidant and hepatoprotective activities of five eggplant varieties. Food Chem. Toxicol. 2010 , 48 , 3017–3021. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Piao, X.-M.; Chung, J.-W.; Lee, G.-A.; Lee, J.-R.; Cho, G.-T.; Lee, H.-S.; Ma, K.-H.; Guo, J.; Kim, H.S.; Lee, A.S.-Y. Variation in antioxidant activity and flavonoid aglycones in eggplant ( Solanum melongena L.) germplasm. Plant Breed. Biotechnol. 2014 , 2 , 396–403. [ Google Scholar ] [ CrossRef ] [ Green Version ]
• Plazas, M.; Nguyen-Huu, T.; Orenga, S.G.; Fita, A.; Vicente, O.; Prohens, J.; Boscaiu, M. Comparative analysis of the responses to water stress in eggplant ( Solanum melongena ) cultivars. Plant Physiol. Biochem. 2019 , 143 , 72–82. [ Google Scholar ] [ CrossRef ]

Share and Cite

Sharma, M.; Kaushik, P. Biochemical Composition of Eggplant Fruits: A Review. Appl. Sci. 2021 , 11 , 7078. https://doi.org/10.3390/app11157078

Sharma M, Kaushik P. Biochemical Composition of Eggplant Fruits: A Review. Applied Sciences . 2021; 11(15):7078. https://doi.org/10.3390/app11157078

Sharma, Meenakshi, and Prashant Kaushik. 2021. "Biochemical Composition of Eggplant Fruits: A Review" Applied Sciences 11, no. 15: 7078. https://doi.org/10.3390/app11157078

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Open Access

Peer-reviewed

Research Article

Field Performance of Bt Eggplants ( Solanum melongena L.) in the Philippines: Cry1Ac Expression and Control of the Eggplant Fruit and Shoot Borer ( Leucinodes orbonalis Guenée)

* E-mail: [email protected] ; [email protected]

Affiliation Institute of Plant Breeding/CSC, College of Agriculture, University of the Philippines Los Baños, College, Laguna, 4031, Philippines

Current address: Bioprotection Research Centre, Lincoln University, Lincoln, 7647 Christchurch, New Zealand

Affiliation International Service for the Acquisition of Agri-Biotech Applications, Los Baños, Laguna, 4030, Philippines

Affiliation International Programs, Cornell University, Ithaca, New York, 14853, United States of America

Affiliation Department of Entomology, Cornell/NYSAES, Geneva, New York, 14456, United States of America

• Desiree M. Hautea, 
• Lourdes D. Taylo, 
• Anna Pauleen L. Masanga, 
• Maria Luz J. Sison, 
• Josefina O. Narciso, 
• Reynaldo B. Quilloy, 
• Randy A. Hautea, 
• Frank A. Shotkoski, 
• Anthony M. Shelton

• Published: June 20, 2016
• https://doi.org/10.1371/journal.pone.0157498
• Reader Comments

Plants expressing Cry proteins from the bacterium, Bacillus thuringiensis (Bt), have become a major tactic for controlling insect pests in maize and cotton globally. However, there are few Bt vegetable crops. Eggplant ( Solanum melongena ) is a popular vegetable grown throughout Asia that is heavily treated with insecticides to control the eggplant fruit and shoot borer, Leucinodes orbonalis (EFSB). Herein we provide the first publicly available data on field performance in Asia of eggplant engineered to produce the Cry1Ac protein. Replicated field trials with five Bt eggplant open-pollinated (OP) lines from transformation event EE-1 and their non-Bt comparators were conducted over three cropping seasons in the Philippines from 2010–2012. Field trials documented levels of Cry1Ac protein expressed in plants and evaluated their efficacy against the primary target pest, EFSB. Cry1Ac concentrations ranged from 0.75–24.7 ppm dry weight with the highest in the terminal leaves (or shoots) and the lowest in the roots. Cry1Ac levels significantly increased from the vegetative to the reproductive stage. Bt eggplant lines demonstrated excellent control of EFSB. Pairwise analysis of means detected highly significant differences between Bt eggplant lines and their non-Bt comparators for all field efficacy parameters tested. Bt eggplant lines demonstrated high levels of control of EFSB shoot damage (98.6–100%) and fruit damage (98.1–99.7%) and reduced EFSB larval infestation (95.8–99.3%) under the most severe pest pressure during trial 2. Moths that emerged from larvae collected from Bt plants in the field and reared in their Bt eggplant hosts did not produce viable eggs or offspring. These results demonstrate that Bt eggplant lines containing Cry1Ac event EE-1 provide outstanding control of EFSB and can dramatically reduce the need for conventional insecticides.

Citation: Hautea DM, Taylo LD, Masanga APL, Sison MLJ, Narciso JO, Quilloy RB, et al. (2016) Field Performance of Bt Eggplants ( Solanum melongena L.) in the Philippines: Cry1Ac Expression and Control of the Eggplant Fruit and Shoot Borer ( Leucinodes orbonalis Guenée). PLoS ONE 11(6): e0157498. https://doi.org/10.1371/journal.pone.0157498

Editor: Juan Luis Jurat-Fuentes, University of Tennessee, UNITED STATES

Received: March 17, 2016; Accepted: May 31, 2016; Published: June 20, 2016

This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.

Data Availability: Data are available from Dryad (doi: 10.5061/dryad.ks131 ).

Funding: This research was funded through the United States Agency for International Development (USAID Cooperative Agreement GDG-A-00-02-00017-00) to Cornell University Agricultural Biotechnology Support Project II (ABSPII), and matching funds from the Republic of the Philippines Department of Agriculture- Biotechnology Program Office (DA- Biotech BPO) and the University of the Philippine Los Banos (UPLB). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

Introduction

Since their introduction in 1996, maize and cotton expressing insecticidal proteins derived from the soil bacterium Bacillus thuringiensis (Bt) have been widely adopted and in 2014 were planted on 78.8 million ha in 28 countries predominantly by resource-poor farmers [ 1 ]. Bt crops are another form of host plant resistance, the foundation for integrated pest management (IPM) programs [ 2 ]. Several major maize and cotton pests have been successfully controlled, and insecticide use on them has been substantially reduced throughout most adopting countries [ 3 ]. Unfortunately, the development of Bt crops has been limited to major commodity crops (maize, cotton, and soybean) and not fruit and vegetables, except sweet corn. This situation is especially unfortunate since fruit and vegetables, when taken together, receive more insecticides than maize, cotton and rice combined [ 4 ].

Eggplant, Solanum melongena L. (also known as brinjal and aubergine) is one of the most important, inexpensive and popular vegetable crops grown and consumed in Asia. In the Philippines, eggplant production accounts for more than 30.0% of the total volume of production of the most important vegetables in the country [ 5 ]. Eggplant production provides an important source of cash income, particularly for small, resource-poor farmers. The biggest constraint to eggplant production throughout Asia is the chronic and widespread infestation by the eggplant fruit-and-shoot borer (EFSB), Leucinodes orbonalis Guenée [ 6 ]. The larvae damage eggplant by boring into the petiole and midrib of leaves and tender shoots resulting in wilting and desiccation of stems. Flowers are also fed upon resulting in flower drop or misshapen fruits. The most serious economic damage caused by EFSB is to the fruit by producing holes, feeding tunnels and frass (or larval excrement) that make the fruit unmarketable and unfit for human consumption. At high pest pressure, EFSB damage in the Philippines results in yield loss of up to 80.0% of the crop [ 7 ]. Surveys of eggplant farmers in the major eggplant growing provinces of the Philippines [ 7 – 11 ] revealed that almost all of them use chemical insecticides to control EFSB because other control measures such as manual removal of EFSB-damaged fruits and wilted shoots, use of biological control arthropods and pheromone traps [ 12 ] have proven ineffective, impractical and expensive. Eggplant farmers in the Philippines employ frequent applications (20–72 times for 5–6 months/season) of mixtures of insecticides to control EFSB, which increase production costs and pose risks to human health and the environment. Studies conducted in Sta. Maria, Pangasinan [ 8 , 13 , 14 ] showed frequent use of broad-spectrum insecticides including profenofos, triazophos, chlorpyrifos, cypermethrin, and malathion. Residues of these insecticides were detected in the soil of eggplant farms and in harvested fruits [ 14 ]. Farmers and farm workers in the study attributed various ailments such as skin irritation, redness of the eyes, muscle pains and headaches to exposure to these pesticides.

After more than 40 years, conventional breeding has not produced any commercial variety of eggplant conferring high level of resistance to the EFSB [ 15 ]. Therefore, efforts became focused on developing Bt eggplant that expresses the same Cry1Ac protein as the cotton event MON531, which has been approved by regulatory agencies in many countries [ 16 – 18 ]. MON531 has been bred into cotton varieties that have been on the global market for almost 20 years with no verifiable report of any adverse effect on human health or the environment. The modified gene used in MON531 encodes an amino acid sequence that is 99.4% identical to the naturally occurring microbial Cry1Ac protein [ 19 , 20 ].

Maharashtra Hybrid Seeds Co. Pvt. Ltd. (Mahyco) inserted the cry1Ac gene under the control of the constitutive 35S CaMV promoter into eggplant to control feeding damage caused by EFSB [ 21 ]. The transformation event designated as 'EE-1' was introgressed into eggplant varieties and hybrids in India, Bangladesh and the Philippines [ 22 , 23 ]. In 2009, although the Indian biosafety regulatory agency gave biosafety approval to Mahyco event EE-1, the Ministry of the Environment and Forests placed a moratorium on its cultivation in India [ 24 ] that remains in effect as of May 2016. In 2013, four Bt eggplant varieties containing the same EE-1 event were conditionally approved for cultivation in Bangladesh. These were grown on 20 fields in 2014 and the number increased to 108 farms in 2015 ( https://bteggplant.wordpress.com/2015/08/11/speech-by-dr-md-rafiqul-islam-mondal-director-general-bari/ ). In the Philippines, event EE-1 was introgressed into selected EFSB-susceptible eggplant open-pollinated (OP) varieties through conventional backcrossing coupled with diagnostic EE-1 event-specific PCR and a cry1Ac gene strip assay [ 25 ]. Five promising advanced Bt OP lines, developed by the University of the Philippines Los Baños, were selected for Confined Field Trial testing in selected eggplant growing areas of the country.

The studies presented in this report contain the first data on Bt eggplant for control of EFSB in Asia to be submitted to a peer-reviewed journal. The studies were conducted with the following objectives: (1) to determine the expression levels of Cry1Ac protein in Bt eggplant OP lines; and (2) to evaluate the field efficacy of the EE-1 event in Bt eggplant OP lines against field populations of EFSB. Results of these studies will be used to generate crucial information for selecting the best EFSB-resistant Bt eggplant OP lines for market release in the Philippines.

Bt Cry1Ac protein expression in different plant parts in Bt Eggplant OP lines

Significant differences were detected in Cry1Ac protein expression among the different plant parts in all Bt eggplant OP lines grown for two seasons ( Fig 1 , S1 Table ). The highest levels of Cry1Ac protein were detected in the terminal leaves, with decreasing levels of expression in the flowers, fruits, stem and roots. Results of the gene strip test of the non-Bt eggplant comparators (near-isoline counterparts and check) were negative and the quantitative ELISA values were below the limit of quantitation (LOQ = 0.125) of the assay used.

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Mean ± SEM Cry1Ac protein concentration in terminal leaves, flowers, fruits, stem, and roots of five (5) Bt eggplant OP lines. n = 4 per plant part/Bt line with 5–10 sample plants per replicate plot. Confined field trial1 (wet/off season) and trial 2 (dry season), CY 2010–2011, Pangasinan, Philippines.

https://doi.org/10.1371/journal.pone.0157498.g001

Terminal Leaves.

The Cry1Ac protein expressed in terminal leaves ranged from 18.32–24.87 ppm dry weight (DW) in trial 1, and 20.40–21.83 ppm DW in trial 2. Line M4 expressed significantly less Cry1Ac protein than line D2 in trial 1; however there were no other significant differences in expression levels among the Bt eggplant lines in either trial.

There were no significant differences detected in Cry1Ac protein content among the Bt eggplant lines in both trials. Cry1Ac protein content in the flowers ranged from 10.17–16.33 ppm DW in trial 1, and from 14.34–17.57 ppm DW in trial 2.

Fruits (flesh and skin).

There were no significant differences in Cry1Ac protein expression in either the fruit flesh or the skin among the Bt eggplant lines tested in both trials. However, the widest range of variation was observed between the two trials. In trial 1, the fruit flesh contained higher levels of Cry1Ac protein at 9.00–16.23 ppm DW and the fruit skin ranged from 8.82–13.42 ppm DW, but much lower levels of Cry1Ac protein were detected in both the flesh and skin in trial 2 (3.02–9.47 and 2.61–7.18 ppm DW, respectively).

There were no significant differences in Cry1Ac protein expression in the stem among all Bt eggplant lines tested. The stem contained Cry1Ac protein concentration of 2.75–5.22 ppm DW in trial 1 and 5.00–7.02 ppm DW in trial 2.

The roots contained the lowest levels of Cry1Ac protein. The mean Cry1Ac protein concentration (1.8 ppm DW) was similar in both trials. There were no significant differences in Cry1Ac protein expression in the roots among the Bt eggplant lines tested. The highest level of Cry1Ac protein expressed in the roots was 2.64 ppm DW.

Cry1Ac protein expression in terminal leaves at different growth stages in Bt Eggplant OP lines

Significant differences in Cry1Ac protein expression were detected in terminal leaves across three growth stages of eggplant development in all Bt eggplant OP lines in both trials ( Fig 2 , S2 Table ). The observed pattern of Cry1Ac protein expression generally increased from the vegetative stage to the reproductive stage; then at the late reproductive stage the levels slightly decreased in trial 1 but increased in trial 2. Higher concentrations of Cry1Ac protein were detected in trial 2 at the vegetative stage (18.69–19.22 ppm DW) and late reproductive stage (22.32–23.54 ppm DW) compared with amounts detected at the same growth stages during trial 1. Significant differences were observed among the Bt eggplant lines in the amount of Cry1Ac protein expressed during the vegetative and reproductive stages in trial 1. Bt eggplant line M4 showed the lowest level of Cry1Ac protein expression among the lines tested. However, no significant differences were observed among the Bt eggplant lines at all growth stages in trial 2.

Mean ± SEM Cry1Ac protein concentration in the terminal leaves of 5 Bt eggplant OP lines at the vegetative, reproductive and late reproductive stages. n = 4 per growth stage/line with 5–10 plants per replicate plot. Confined field trial 1 (wet/off season) and trial 2 (dry season), CY 2010–2011, Pangasinan, Philippines.

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Control of EFSB by Bt Eggplant OP lines

Under natural field infestations, the efficacy against EFSB of Bt eggplant lines and the non-Bt comparators (near-isoline counterparts and check variety) were evaluated for three seasons (trials 1–3) based on the following parameters: % EFSB-damaged shoots, % EFSB-damaged fruits and number of EFSB larvae in fruits. Throughout the sampling/harvest periods, Bt eggplant lines consistently demonstrated a lower percentage of EFSB-damaged shoots ( Fig 3 , S3 Table ), % EFSB- damaged fruits ( Fig 4 , S4A to S4C Table ) and number of EFSB larvae in fruits ( Fig 5 , S4A to S4C Table ) compared to the conventionally-bred non-Bt eggplant comparators.

Mean ± SEM percentage (%) EFSB-damaged shoots in Bt lines and their non-Bt eggplant comparators at different sampling periods. n = 4 per entry with 16 plants per replicate plot. Confined field trials 1 and 3 (wet/off season) and trial 2 (dry season), CY 2010–2012, Pangasinan, Philippines.

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Mean ± SEM percentage (%) EFSB-damaged fruits in Bt lines and their non-Bt eggplant comparators at different harvest periods. n = 4 per entry with 16 plants per replicate plot. Confined field trials 1 and 3 (wet/off season) and trial 2 (dry season), CY 2010–2012, Pangasinan, Philippines.

https://doi.org/10.1371/journal.pone.0157498.g004

Mean ± SEM number of EFSB larvae in damaged fruits of Bt lines and their non-Bt eggplant comparators at different harvest periods. n = 4 per entry with 16 plants per replicate plot. Confined field trials 1 and 3 (wet/off season) and trial 2 (dry season), CY 2010–2012, Pangasinan, Philippines.

https://doi.org/10.1371/journal.pone.0157498.g005

Significant differences among entries ( P = <0 . 0001 ) were detected in all parameters measured in the three trials. Results of paired mean comparison by contrast for all parameters and corresponding level of control (% efficacy) relative to non-Bt eggplant are presented in Table 1 . Highly significant differences were consistently detected between Bt eggplant lines and their corresponding non-Bt eggplant comparators for all parameters in every trial. Comparisons between Bt eggplant lines and non-Bt eggplant comparators showed significantly lower shoot and fruit damage and fewer surviving EFSB larvae in fruits in the Bt eggplant lines tested. Bt eggplant demonstrated 97.7–100% and 96.0–100% control of EFSB shoot and fruit damage, respectively, except in Bt line M4 in trial 1. This line had slightly lower % efficacy for shoot damage (95.3%) and fruit damage (94.1%) but these levels were significanly much better than any of the the non-Bt comparators. Control of EFSB larval infestation in Bt eggplant lines ranged from 88.4–100%, with most lines showing > 96.0% control, except for Bt M1 and M8 in trial 1. Nevertheless, the levels of control of EFSB larval infestation in M1 and M8 were still far better compared to any of the non-Bt comparators tested.

https://doi.org/10.1371/journal.pone.0157498.t001

Seasonal variation in field damage was also observed between Bt eggplant lines and their non-Bt comparators ( Table 1 ). Trials 1 and 3 were conducted during the wet/off planting season when most of the surrounding annual crop was rice. Trial 2 was conducted during the dry season, when eggplants are more widely grown in Pangasinan. Of the three trials conducted, the highest pest pressure was recorded during trial 2 as evidenced by the highest percentages of plant damage and number of insects observed. During trial 2, the highest mean % EFSB-damaged shoots (41.58%), % EFSB-damaged fruits (93.08%), and number of surviving EFSB larvae (16.15 larvae/plot/harvest) were recorded in the non-Bt eggplant comparators. Under such severe pest pressure, the Bt eggplant lines showed <1% EFSB shoot damage, <2% fruit damage and fewer EFSB larvae (<1 larva/plot/harvest).

Survival and Fecundity of EFSB in Bt Eggplant OP lines

EFSB larvae were collected from plants of Bt eggplant lines and non-Bt comparators and brought to the Entomology laboratory and reared continuously in their respective hosts. The results showed that very few EFSB larvae were collected in all Bt eggplant compared with the non-Bt eggplant plants sampled ( Table 2 ). Of the total (27) EFSB larvae reared from Bt eggplant plants, less than half (11/27) emerged as adults and almost half (5/11) of the moths were weak and died before mating. Only six adults were able to mate successfully. However, no viable eggs and offspring resulted from any paired matings involving either male or female EFSB adults collected and reared in the Bt eggplants ( Table 3 ). In contrast, a high percentage (97.3%) of EFSB larvae collected from the non-Bt plants successfully emerged as adults, mated and produced many viable eggs and young larvae.

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https://doi.org/10.1371/journal.pone.0157498.t003

Spatio-Temporal Expression of Cry1Ac Protein in Bt Eggplant Lines

Recent reviews [ 18 , 26 , 27 ] of Bt crops engineered to express δ-endotoxin proteins cited numerous reports indicating that the expression of Cry proteins vary with plant parts, plant age, genotypes and environmental conditions. To provide the greatest benefits, Cry proteins should be expressed in sufficient quantities to provide high levels of protection to appropriate plant parts and at the stage of growth when the target insect pest pressure is most severe. In this study, significant differences were detected in the amount of Cry1Ac expressed in different plant parts: terminal leaves > flowers > fruits > stem > roots. Cry1Ac expression in the pollen was below the limit of quantitation (LOQ) of the assay used (LOQ = 0.125) (unpublished greenhouse data). It is noteworthy that higher amounts were detected in plant parts preferably attacked by the primary target pest, EFSB. The level of expression of Cry1Ac in Bt eggplant lines tested varied between 0.75±0.33 to 24.87±0.56 ppm DW. These findings are consistent with previous studies conducted in the Philippines [ 25 ] and India [ 21 , 28 ] showing that Bt eggplants have higher levels of Cry1Ac protein expressed in the terminal leaves, flowers and fruits than in the stem and roots. Similarly, a number of studies conducted in other countries also reported variability in Cry protein expression in plant parts in other Bt crops including cotton [ 29 – 31 ], corn [ 32 – 34 ] and rice [ 35 ].

Many researchers have also reported variation in Cry1Ac protein expression in Bt cotton during the growth and development of the plant [ 36 – 42 ]. In Bt cotton, Cry1Ac protein levels were generally high at early stages and then declined as the plant grew to maturity [ 31 , 43 ]. In this study, seasonal variation was also detected in the level of Cry1Ac protein expression in the terminal leaves of Bt eggplant lines. However, the amount of Cry1Ac protein expressed varied only up to 1.7-fold throughout the growing season of 120 days required for profitable eggplant production. Contrary to the results in Bt cotton, in this study the level of Cry1Ac protein expression significantly increased from the vegetative stage to the reproductive stage and either slightly declined or increased at the late reproductive stage depending on the trial. It is important to note that the amount of Cry1Ac protein expressed in Bt eggplant OP lines peaked during the fruit-bearing stage and remained high with the average at 20–23 ppm DW as EFSB pest pressure became more severe.

Factors Affecting Variability in Cry1Ac Protein Expression in Bt Eggplant Lines

Data from other crops also suggest that factors inherent to the variety and the environment affect the variability of Cry1Ac expression. These factors include among others, transgene promoter, parental background, and environmental stressors such as high temperature, heavy drought, waterlogging, and insect damage [ 38 , 44 , 45 ]. In this study, variability in Cry1Ac protein expression in the Bt eggplant lines could also be attributed to using the constitutive 35S CaMV promoter in the EE-1 gene construct, as suggested in studies with Bt cotton which used the same promoter. Parental background has also been reported to affect Cry1Ac protein variability in Bt cotton [ 30 , 31 ]. In this study, the parental background (‘Mara’ and ‘DLP’) of the Bt eggplant OP lines may have influenced, but only to a limited extent, the spatio-temporal variability in Cry1Ac expression. Finally, environmental factors could have contributed to the spatio-temporal expression of the Cry1Ac protein in Bt eggplant lines. Results showed that the levels of Cry1Ac detected during the entire growing season during trial 2 were different compared to results from trial 1. Trial 1 was conducted during the off-season eggplant planting, while trial 2 was conducted during the regular dry season planting. During trial 2, there were more eggplant planted, hence the level of EFSB pest pressure was higher during this season resulting in more damage as shown in the field efficacy data. Weather data obtained during the duration of the two trials indicated that the average daily temperature was similar but the amount of rainfall was much higher in trial 1 than trial 2. A previous report [ 46 ] suggested that environmental factors such as temperature and insect damage could influence expression of a Cry protein.

Variation in Cry1Ac Protein Expression and its Effects on Field Efficacy of Bt Eggplant Lines

It has been a key concern for developers of Bt crops whether variation in Cry protein expression may cause variation in control of the target insect pest. A number of studies in Bt cotton showed that concentration of Cry1Ac correlates well with the efficacy against the target insect pests and that, as the amount of Cry1Ac declines when the crop matures, there is a concomitant decrease in % mortality of the target pest, bollworm ( Helicoverpa armigera or Helicoverpa zea ) [ 29 , 37 , 39 , 47 – 49 ]. In this study, the highest concentration of Cry1Ac protein was expressed in the terminal leaves (24.87± 0.56 ppm DW) and remained high as the Bt eggplant crop matured. The field efficacy of Bt eggplant lines, measured as % EFSB-damaged shoots, also remained very high (95.4–100% reduction) during the entire 10 weeks of evaluation. These results suggest that the high level of expression of Cry1Ac protein results in high field efficacy in Bt eggplant lines. The reduced EFSB-damaged shoots indicate that the effective control of EFSB starting at the vegetative stage will help reduce the field population of EFSB during the fruit-bearing stage resulting in much reduced EFSB damage. Among the plant parts, the level of Cry1Ac protein expressed in the fruits (flesh and skin) was intermediate (2.61±0.36–12.52±3.41 ppm DW). Nevertheless, the % EFSB-damaged fruits in Bt eggplants were effectively reduced (94.1–100% control) throughout the reproductive period of the plants. It should be noted that the lowest concentrations of Cry1Ac detected in the shoots (18.32±2.45 ppm DW) and fruits (2.61±0.36 ppm DW) in the Bt eggplant lines were well above the baseline susceptibility benchmark values of L . orbonalis for Cry1Ac previously reported from India. The average moult inhibitory concentration, MIC 95 , from 29 L . orbonalis populations tested for Cry1Ac was 0.059 ppm [ 21 , 28 ]. More recent work reported the baseline limits for MIC 50 = 0.003 to 0.014 ppm and MIC 95 = 0.028 to 0.145 ppm [ 50 ]. The median lethal concentrations reported were LC 50 = 0.020 and 0.042 ppm [ 50 ] and LC 50 = 0.0326 to 0.0369 mg/mL and LC 90 = 0.0458 to 0.0483 mg/mL of diet [ 51 ]. MIC values have been used in corn as the best estimator of "functional mortality" and predictor of potential effectiveness of Bt corn [ 52 ].

Field Efficacy of Bt Eggplant Lines Containing Event EE-1 Against the Primary Target Pest, ESFB

Efficacy is the capacity of the host plant to affect the survival of the insect pest. Host plant resistance can be measured as a percentage of damage to the foliage or fruiting parts, reduced crop stand, yield and vigor [ 53 ]. It can also be measured based on insect characteristics which include number of eggs laid, aggregation, food preference, growth rate, food utilization, mortality and longevity. In this study, the field efficacy of Bt eggplants against EFSB was evaluated based on the following parameters: (1) percentage of EFSB-damaged shoots; (2) percentage of EFSB-damaged fruits; (3) EFSB larval counts; and (4) survival and fecundity of field collected larvae.

The results of the three season trials indicated consistent, high field efficacy in all Bt eggplant lines tested relative to their non-Bt eggplant comparators i.e. non- Bt near-isoline counterparts and check variety. Even under the most severe pest pressure during trial 2, the Bt eggplant lines demonstrated high level of control of EFSB shoot damage (98.6–100%) and fruit damage (98.1–99.7%) and reduced EFSB larvae infestation (95.8–99.3%). Among the lines tested, Bt M4 showed the lowest % efficacy in shoot (95.3%) and fruit damage (94.1%) and M8 the lowest % efficacy for EFSB larval count (88.4%). However, these lower results were not consistently observed in every trial and their efficacy levels were always much better compared to any of the non-Bt comparators tested.

In addition to Cry1Ac expression and plant damage, we assessed the effect of Bt eggplants on EFSB survivorship and fecundity. This was done to assess the potential for evolution of resistance of EFSB to Bt eggplant. Resistance among insects occur when genetic variation in a population enables a subset of individuals to survive on doses lethal to the majority of the population when feeding on the Bt plant and subsequently produce viable offspring [ 54 , 55 ]. It is noteworthy that results showed few adults emerged and no eggs and viable offspring were produced in mating adults from larvae collected in Bt eggplant lines lending further evidence of very high field efficacy against EFSB. Furthermore, the diminished capacity for normal insect development and reproduction suggest the Bt eggplant lines tested in these trials express a high dose, a key component in the high dose-refuge management strategy [ 56 ].

Taken together, the results obtained from the two-year field testing in Pangasinan support the conclusion that Bt eggplant OP lines developed by the University of the Philippines Los Baños and containing event EE-1 possess a novel trait that provides outstanding control of EFSB making them superior to the conventional counterparts and the check, particularly when the pest pressure is high. Commercial production of Bt eggplant has great potential to reduce yield losses to EFSB while dramatically reducing the reliance of growers on synthetic insecticides to control this pest, reducing risks to the environment, to worker's health, and to the consumer [ 7 , 8 , 10 , 57 ].

Before Bt eggplant seeds are made available for commercial propagation, it is essential to develop an insect resistance management (IRM) plan to manage the risk of resistance evolution in the target pest. The use of high-dose/refuge strategy has been postulated to delay the potential evolution of insect resistance to the Bt crops by maintaining insect susceptibility [ 56 ]. This has been implemented for Bt cotton and Bt corn and the same needs to be extended to Bt eggplants. Some of the key elements in an IRM strategy include information on the expression profile of an insecticidal protein in the Bt crop, the inherent susceptibility of the insect, the number and dominance of genes involved, and the availability of susceptible plants as refuge. Results of the studies presented in this paper indicate that Bt eggplant OP lines expressed the Cry1Ac protein in relevant plant parts primarily attacked by EFSB at the appropriate growth stages throughout the productive life of the crop. More importantly, the amount of Cry1Ac detected in the Bt eggplant shoots and fruits remained sufficiently high to have significant activity against EFSB when compared to the baseline limits previously reported [ 21 , 28 , 50 , 51 ]. Furthermore, the Bt eggplant OP lines exhibited very high levels of field efficacy against EFSB and severely diminished the capacity of EFSB to reproduce successfully.

Prior to the commercial production of Bt eggplant in the Philippines, a structured refuge management strategy will be required. In addition to a structured refuge, the presence of many conventional non-Bt eggplant varieties and alternate wild Solanum hosts commonly present in uncultivated peripheral lands (i.e., unstructured refuges) will serve as a source of susceptible EFSB alleles in the population to slow the evolution of resistance in EFSB. Collectively, the results of this study suggest the possibility of a high-dose/refuge strategy for Bt eggplants. A stringent implementation of high-dose/refuge IRM plan within the context of integrated pest management (IPM) could help delay the potential development of resistance of EFSB to the Bt protein in UPLB Bt eggplant lines.

Materials and Methods

Confined field trials were conducted in the Philippines to evaluate product performance and assess potential environmental risks of UPLB Bt eggplants compared to their non-Bt comparators i.e. non-Bt near-isoline counterparts and the commercial check or reference variety. The field testing site located in the province of Pangasinan, the Philippines, best represented the agro-climatic conditions and production practices in the largest eggplant growing region (Region I or the Ilocos Region) in the country. Pangasinan has Type 1 climate characterized by two pronounced growing seasons: dry, from November to April; wet, during the rest of the year. Eggplant cultivation in Pangasinan is higher during the dry season (DS). Farmers in Pangasinan plant eggplant after rice starting in the months of September to October (planting season) and harvest during the months of December to April. Some farmers also plant during the off-season, which starts at the end of the dry season and harvest during the early wet-season. The province of Pangasinan alone has the widest production area (18.4%) and contributes the largest volume (31.9%) of eggplant produced in the country (2005–2014) [ 5 ]. The Pangasinan field trial site represented the conditions in small-holder farmer’s fields that experience very high natural incidence of EFSB pressure compared with other trial sites.

Three replicated confined field experiments were conducted in Bgy. Paitan, Sta. Maria, for three seasons from March 2010- October 2012. These trials were conducted under natural field infestation of EFSB and without application of lepidopteran-specific insecticide sprays. The studies were conducted in a comparative manner. Bt eggplant lines were evaluated in comparison with the conventional non-Bt comparators consisting of the corresponding non-Bt counterparts with similar genetic backgrounds (recurrent parents/near-isolines) and a National Seed Industry Council (NSIC)-approved commercial open-pollinated variety (OPV) as check or reference genotype. OPVs are standard varieties, which have stable characteristics and produce seeds that will grow into plants more or less identical to their parent plants.

Plant Materials, Experimental Design and Regulatory Conditions

The experimental materials used in the series of three confined field experiments are listed in Table 4 .

https://doi.org/10.1371/journal.pone.0157498.t004

Plant materials.

The Bt eggplant OP lines (D2, D3, M1, M4, M8) used as test entries in the field trials are advanced breeding lines (BC 3 F 4 to BC 3 F 6 ) derived from initial crosses of Mara selection x Mahyco elite line, ‘EE-1’ and DLP selection x Mahyco elite line, ‘EE-1’. The non-Bt comparators were: (1) DLP as the non-Bt counterpart genotype of Bt D2 and D3 OP lines; (2) Mara, Mara 1 or Mara S2 as the counterpart genotypes for M1, M4 and M8; and (3) Mamburao, a non-Bt eggplant OP variety approved by the NSIC [ 58 ] as the check or reference genotype.

Experimental Design and Field Layout.

Each field experiment was planted in randomized complete block design (RCBD) with four replications, 4–6 rows/plot and 10 plants per row. The perimeters of each field experiment were surrounded by five rows (1 m between rows) of conventional non-Bt eggplant OP as pollen-trap plants. The experimental set up was conducted in a fenced facility with restricted access. A 200-meter radial distance isolated the field trial site from the nearest eggplants in the area.

Permissions.

All field trials were conducted in accordance with the Department of Agriculture Administrative Order No. 8 Series of 2002 for field testing ( www.biotech.da.gov.ph ). The Bureau of Plant Industry (BPI) issued the corresponding Biosafety Permit for Field Testing in Bgy. Paitan, Sta. Maria, Pangasinan. The biosafety permit conditions were complied with throughout the conduct of every field experiment and associated greenhouse and laboratory activities. All sample collection and transport of materials were done under the supervision of the duly designated biosafety trial inspectors following the prescribed biosafety procedure for sample collection, handling and transport.

Crop Establishment, Management, Harvesting and Termination

Seedling establishment..

Seeds of UPLB Bt and non-Bt eggplant entries (treatments) were sown in pots with sterilized soil 30–34 days before transplanting. The germinated seeds were pricked (transferred individually in seedling trays), 7–8 days after sowing (DAS) and maintained inside the BL2 greenhouse at UP Los Baños. At 28–30 DAS, representative seedlings for the seed lot of each entry were tested for presence or absence of Cry1Ac using immunoassay or gene strip test kit, DesiGen Xpresstrip (DesiGen, Maharashtra, India), as described in Ripalda et al . [ 25 ]. Excess transgenic seedlings were disposed of properly in a disposal site inside the BL2 greenhouse. Seedlings of Bt and non-Bt eggplant test entries, check varieties and pollen traps were transported from UP Los Baños to the confined field testing site in Bgy. Paitan, Sta. Maria, Pangasinan for transplanting.

Cultural management.

The confined field trials were managed based on the national cooperative trial guidelines for eggplant [ 59 ] and prevalent agronomic practices for eggplant growing in the region, including site preparation, tillage, and nutrient applications. Manual watering of plants was done during the first month after transplanting and shifted to overhead and/or furrow irrigation as plants grew and required greater amounts of water. At times of continuous heavy rain during the trial period, trenches or canals were dug to keep the soil near the roots from being waterlogged and to reduce the incidence of bacterial wilt infection. Staking of plants was done to provide additional support as the number and size of fruits increase and during periods of strong winds and rain. Branches were kept off the ground to prevent the fruit from becoming deformed.

Pest management.

No lepidopteran-specific insecticide sprays were applied during the entire duration of the trials. Management of other arthropod pests and diseases was done by application of recommended IPM practices, primarily sanitation and withholding of pesticide use as long as possible to enable the proliferation of natural enemies. Whenever populations of leafhoppers and mites rose to very high level, they were controlled with the application of insecticides with reduced risk and without activity against EFSB (a.i. thiamethoxam) and sulphur, respectively.

Termination, disposal and fallow period.

After the final harvest, each field experiment was terminated. All above- and below- ground plant parts were removed from the field and disposed of properly following the prescribed procedure indicated in the Biosafety permit. The field was plowed, irrigated and observed for volunteer plants 7, 14 and 30 and 60 days after termination. The field was kept fallow for at least 60 days after termination.

Data Collection and Analysis

Determination of cry1ac protein expression..

Cry1Ac protein expression study was conducted in trial 1 and trial 2, which represented the two eggplant growing seasons in Pangasinan, i.e. wet/off-season and regular dry season planting, respectively. Because trial 3 was also planted during the same season as trial 1 (wet/off-season) and for cost consideration, Cry1Ac protein analysis was not performed from samples obtained in this trial.

Sample collection used was based on the protocol previously described in Ripalda et al . [ 25 ]. Different plant parts from at least five plants from among the 16 plants in the two inner rows/replicate plot were collected. Terminal leaves were collected at the vegetative (up to 25 days after transplanting, DAT), reproductive (25–60 DAT) and late reproductive (60–80 DAT) stages of the crop. Flowers and immature fruits were collected during reproductive and late reproductive stages. Fruit samples were collected during the harvest period. Stem and roots were collected at termination (around 150 DAT). All samples collected were kept in an icebox and transported to the laboratory. Flesh and skin of immature fruits, but avoiding seeds, were separated in thin slices. Stems and roots were washed prior to storage. The woody portion of the stems was used for analysis. All samples were kept in a -80°C biofreezer until further processing and then freeze-dried at -60°C for 1–5 days until crisp. Dried samples from three plants per plot per plant part were bulked and placed in a 2.0 mL microfuge tube. Bulked samples were homogenized using two 6-mm steel beads and the ground samples were put in sealed containers and stored at 4°C until use.

Quantification of Cry1Ac was done through an enzyme-linked immunosorbent assay (ELISA). Commercially available quantitative ELISA kits (DesiGen Cry1Ac QuanT) specific for the Cry1Ac protein were procured from Mahyco (Maharashtra, India). Five milligrams of the powdered samples were weighed and analyzed. Chilled extraction buffer prepared as specified in the kit was added to the weighed samples. A dilute (up to 1:8) trypsinized protein extract was loaded to the pre-coated plates. Positive and negative controls and standards were prepared and loaded according to the instructions in the kit. Antibodies, wash buffer and substrate for detection (pNPP) used were also from the kit. Absorbance readings of the samples were made at 405 nm. According to the manufacturer’s instruction, the assay is considered valid when the mean absorbance reading of the blank is ≤0.246, mean absorbance reading of the standards with the highest concentration of Cry1Ac is ≥1.305, % residual of back calculated concentration of standards are 20 ng/ml– 125 ng/ml standards: ≤15%; 0.625 ng/ml standard ≤25% and R 2 of the standard curve is ≥0.98.

Data on Cry1Ac concentrations from different plant parts and different developmental stages of the Bt eggplant lines were analyzed by one-way analysis of variance using PROC MIXED in SAS v.9.1.3 [ 60 ]. Means were separated using Tukey’s HSD at α = 0.05. Data available from the Dryad Digital repository: http://dx.doi.org/10.5061/dryad.ks131 [ 61 ]

Evaluation of Field Damage by EFSB.

Fruits were harvested from the 16 plants located in the inner two rows (12 m 2 ) of each plot. During each harvest period, the harvested fruits per plot were carefully cut open and examined for the presence of EFSB larvae or signs of EFSB damage and tunneling, sorted as with or without EFSB-damage, counted and weighed separately.

Data gathered:

• Percentage (%) damaged shoots per plot–calculated from the number of damaged shoots due to EFSB recorded from five shoots per plant from 16 inner row plants per plot at weekly intervals starting at two weeks after transplanting (WAT) for 10 observation periods.
• Percentage (%) damaged fruits per plot—calculated from the total number of EFSB-damaged fruits over the total number of fruits harvested from 16 inner row plants per plot. Harvesting was done every 3–4 days. Data were collected from 10–17 harvest periods prior to the termination of the experiment.
• EFSB larval counts (no. larvae/plot)–All harvested fruits from the 16 inner row plants per were cut open to check for the presence of EFSB larvae. The number of surviving EFSB larvae found inside the fruits per replicate plot were recorded every harvest period.
• % Efficacy (or Level of control)–calculated based on the formula (1- Bt/nonBt)*100% for % EFSB-damaged shoots, damaged fruits and EFSB larval counts
• Survivorship and fecundity–All surviving larvae collected per plot per harvest period were transferred to individual plastic cups and labeled. Each cup was provided with a slice of eggplant fruit from which the larva was collected. The cups were then brought to the UPLB-IPB Entomology P2 Laboratory and reared continuously in their respective hosts (Bt or non-Bt) until the adult stage. The number of individuals that successfully reached pupal and adult stages was recorded. Pairs of surviving adults from Bt and from conventional non-Bt lines were mated, placed in oviposition chambers and observed for egg deposition and hatching of offspring.

Data transformation was used to improve the normality of variables due to markedly skewed data or heterogeneous variances of Bt and conventional non-Bt entries. Data collected were transformed to sqrt (Y+0.5), arcsin (sqrt(Y/100)) or log 10 (Y+1) as appropriate. Transformed data on percentages damaged shoots and fruits, larval counts and feeding tunnel lengths were subjected to one-way analysis of variance and analyzed using PROC MIXED in SAS v.9.1.3 [ 60 ] and means were separated using Tukey’s HSD at α = 0.05. Pairwise mean comparisons by contrast between each Bt and its respective non-Bt counterpart and check variety were done for all parameters gathered using PROC MIXED. Data available from the Dryad Digital repository: http://dx.doi.org/10.5061/dryad.ks131 [ 61 ]

Supporting Information

S1 table. mean ± sem concentration of cry1ac in different plant parts of bt eggplant op lines..

Trials 1 to 2. CY 2010–11, Sta Maria, Pangasinan, Philippines.

https://doi.org/10.1371/journal.pone.0157498.s001

S2 Table. Mean ± SEM concentration of Cry1Ac in the terminal leaves of Bt eggplant OP lines at three different growth stages.

https://doi.org/10.1371/journal.pone.0157498.s002

S3 Table. Mean ± SEM of percentage EFSB shoot damage of Bt OP lines and non-Bt eggplants comparators.

Trials 1 to 3. CY 2010–12, Sta. Maria, Pangasinan, Philippines.

https://doi.org/10.1371/journal.pone.0157498.s003

S4 Table. Mean ± SEM of percentage EFSB fruit damage of Bt OP lines and non-Bt eggplants comparators.

A: Trial 1; B: Trial 2; C: Trial 3. CY 2010–12, Sta. Maria, Pangasinan, Philippines.

https://doi.org/10.1371/journal.pone.0157498.s004

S5 Table. Mean ± SEM EFSB larval counts in fruits of Bt OP lines and non-Bt eggplants comparators.

https://doi.org/10.1371/journal.pone.0157498.s005

Acknowledgments

We gratefully acknowledge the critical support and valuable contributions of these institutions. This research was co-funded by the United States Agency for International Development (USAID) through Cornell University Agricultural Biotechnology Support Project II (ABSPII), the Republic of the Philippines Department of Agriculture- Biotechnology Program Office (DA- Biotech BPO) and the Instiute of the Plant Breeding, College of Agriculture, University of the Philippine Los Baños (UPLB). We thank the Maharashtra Hybrid Seeds Co. Pvt. Ltd. (Mahyco) for providing access to eggplant event EE-1 and regulatory-related information, and for various technical assistance/advice in the conduct of laboratory and field activities; and Cornell University and Sathguru Management Consultants for facilitating the technology transfer. We also acknowledge the assistance of UPLB Foundation Inc., the executing agency for the ABSPII project in the Philippines.

We sincerely thank the following Bt eggplant staff for their various valuable contributions: OO Silvestre, MMM Abustan, RN Candano, RP Urriza, ER Maligalig, SA Baldo and MM Marin for field establishment and management and lab/field data collection; RR Ripalda, RB Frankie, ML de Vera and AD Austral for sampling and Cry1Ac analysis; and ZJ Bugnosen for assistance in regulatory-related and administrative activities. We thank B. Bartolome for statistical advice and JA Estrella and RN Candano for assistance in statistical analyses; and N. Storer for reviewing an earlier draft of the manuscript. Special thanks to the people of Sta. Maria, Pangasinan especially Ret. Gen. M Blando, Dr. R Segui for all forms of assistance during the conduct of the trials.

Author Contributions

Conceived and designed the experiments: DMH RAH JON LDT MLJS FAS AMS. Performed the experiments: JON RBQ LDT MLJS APLM DMH RAH. Analyzed the data: LDT APLM DMH RAH. Wrote the paper: DMH LDT APLM RAH FAS AMS. Developed the breeding materials: JON LDT RBQ DMH RAH. Supervised the field trials: DMH RAH RBQ LDT FAS. Prepared application and obtained all relevant permits for confined field trials: DMH JON LDT RAH.

• 1. James C. Global Status of commercialized biotech/GM crops. Ithaca, NY: International Service for the Acquisition of Agri-biotesh Applications; 2014.
• 2. Kennedy GG. Integration of insect-resistant genetically modified crops within IPM programs. In: Romeis J, Shelton AM, Kennedy GG, editors. Integration of Insect-Resistant, Genetically Modified Crops within IPM Programs. Dordrecht, The Netherlands: Springer; 2008. pp. 1–26.
• View Article
• PubMed/NCBI
• Google Scholar
• 5. Philippines Statistics Authority-Bureau of Agricultural Statistics. CropStat for 2005–2014. Available: http://countrystat.psa.gov.ph/
• 6. Talekar NS. Controlling Eggplant Fruit and Shoot Borer: A Simple, Safe and Economical Approach. Taiwan: Asian Vegetable Research and Development Center; 4p. International Cooperators’ Guide. May 2002. AVRDC Publication No. 02–534.
• 7. Francisco SR. Costs and benefits of UPLB Bt Eggplant with Resistance to Fruit and Shoot Borer in the Philippines. In: Norton GW, Hautea DM, editors. Projected Impacts of Agricultural Biotechnologies for Fruits and Vegetables in the Philippines and Indonesia. Ithaca, NY and Los Banos, Laguna: International Services for the Acquisition of Agri-Biotech Applications and the Southeast Asian Ministers of Education Organization-Southeast Asia Regional Center for Graduate Study and Research in Agriculture; 2009. pp. 35–54.
• 8. Francisco SR. Socioeconomic Impacts of Bt Eggplant: Evidence from Multi-location Field Trials. In: Gerpacio RV, Aquino AP, editors. Socioeconomic Impacts of Bt Eggplant: Ex-ante Case Studies in the Philippines. Ithaca, NY and Los Banos, Laguna: International Services for the Acquisition of Agri-Biotech Applications and the Southeast Asian Ministers of Education Organization-Southeast Asia Regional Center for Graduate Study and Research in Agriculture; 2014. pp 205–232.
• 9. Quicoy C. Productivity and technical efficiency of eggplant production in selected provinces in the Philippines: Stochastic production function approach. 2010. Presentation available: http://www.ajad.searca.org/phocadownload/ADSS 2010/ADSS_Aug24_PRODUCTIVITY AND TECHNICAL EFFICIENCY OF EGGPLANT.pdf
• 10. Quicoy C. The Eggplant Subsector in Davao Region, North Cotabato, Iloilo and Southern Leyte. In: Gerpacio RV, Aquino AP, editors. Socioeconomic Impacts of Bt Eggplant: Ex-ante Case Studies in the Philippines. Ithaca, NY and Los Banos, Laguna: International Services for the Acquisition of Agri-Biotech Applications and the Southeast Asian Ministers of Education Organization-Southeast Asia Regional Center for Graduate Study and Research in Agriculture; 2014. pp 97–125.
• 15. Alam SN, Rashid MA, Rouf MFA, Jhala RC, Patel JR, Satpathy S, et al. Development of an integrated pest management strategy for eggplant fruit and shoot borer in South Asia. Shanhua, Taiwan: AVRDC—the World Vegetable Center. 54p. Technical Bulletin No. 28. 2003. AVRDC Publication No. 03–548.
• 16. Naranjo SE, Ruberson JR, Sharma HC, Wilson L, Wu KM. The present and future role of insect-resistant GM cotton in IPM. In: Romeis J, Shelton AM, Kennedy GG, editors. Integration of Insect-Resistant, Genetically Modified Crops within IPM Programs.Dordrecht, The Netherlands: Springer; 2008. pp. 159–194.
• 17. Center for Environmental Risk Assessment (CERA). GM Crop Database. 2013. Available: http://cera-gmc.org .
• 19. Hammond BG,Koch MS. A review on the food safety of Bt Crops. Dordrecht Netherlands: Springer Science+Business Media B.V.; 2012; pp 305–325.
• 20. Organization for Economic Cooperation and Development. Consensus document on safety information on transgenic plants expressing Bacillus thuringiensis —derived insect control protein. Paris: Organization for Economic Co-operation and Development; 2007. Series on Harmonization of Regulatory Oversight in Biotechnology, No. 42. Available: http://www.olis.oecd.org/olis/2007doc.nsf/LinkTo/NT00002DF6/ $FILE/JT03230592.PDF. Accessed 12 March 2016.
• 21. Choudhary B, Gaur K. Development and regulation of Bt brinjal in India. Ithaca, NY: International Service for the Acquisition of Agribiotech Applications; 2009. ISAAA Brief No. 38.
• 23. Hautea DM, Cruz VM, Hautea RA, Vijayaraghavan V. Transgenic horticultural crops in Asia, pp. 155–174, In: Transgenic Horticultural Crops Challenges and Opportunities. Mou B, Scorza R, editors. Boca Raton, London, New York: CRC Press Taylor and Francis Group. 2011. pp 144–174.
• 28. M/s Mahyco, University of Agricultural Sciences and Tamil Nadu Agricultural University. Report of the Expert Committee (EC-II) on Bt Brinjal Event EE-1. Submitted to Genetic Engineering Approval Committee. New Delhi, India: Ministry of Environment and Forests. October 2009. Available: http://www.moef.nic.in/sites/default/files/Report on Bt brinjal_2.pdf
• 45. Rao CK. Transgenic Bt Technology: 3. Expression of transgenes. In: Foundation for Biotechnology Awareness and Education. Available: http://www.fbae.org/2009/FBAE/website/special-topics_views_transgenic_bt_technology3.html
• 47. Fitt G, Daly JC, Mares CL, Olsen K. Changing efficacy of transgenic Bt cotton—patterns and consequences pp 189–196 In: Pest Management—Future Challenges Volumes 1 and 2. Brisbane, Australia: University of Queensland Printery; 1998. pp 189–196.
• 48. Holt, H (1998). Season-long monitoring of transgenic cotton plants—development of an assay for the quantification of Bacillus thuringiensis insecticidal protein. Proceedings of the 9th Australian Cotton Conference, 12–14 August 1998, Broadbeach, Queensland, 1998. pp 331–335
• 53. Panda N, Khush GS. Host plant resistance to insects. Wallingford: CAB International in association with the International Rice Research Institute. 1995.
• 59. National Seed Industry Council—Vegetable Technical Working Group. Policies and Guidelines for testing vegetable crop varieties. Available: www.nseedcouncil.bpinsicpvpo.com.ph/downloadables/nctveg.pdf
• 60. SAS INSTITUTE. SAS/STAT 9 user’s guide. Cary, NC: SAS Institute, Cary, NC; 2001.

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GROWTH AND YIELD OF EGGPLANT (Solanum melongena L.) ON VARIOUS COMBINATIONS OF N-SOURCE AND NUMBER OF MAIN BRANCH

This research was conducted to increase production of eggplants through combination of N-source and number of main branch has done onthe field of andosol in Poncokusumo - Malang, 600 m asl, pH 5.4, from August to December 2013. The experiment used a Randomized Complete Block Design with 2 factors and 3 replications. Factor 1 was proportion of inorganic - organic N fertilizer (138 kg N ha -1 ): 100% Urea, 75% Urea + 25% goat manure, 50% Urea + 50% goat manure, and 25% Urea + 75% goat manure. Factor 2 was number of main branches: 1, 2 and 3 main branches. Results showed that there was no interaction effect between treatment combinations of organic-inorganic sources of N and the number of main branches to all observed variables. Treatment using the combination of 75% Urea + 25% goat manure increased the plant growth and gave the highest fruit yield (49.20 t ha -1 ) in comparison with combination using other fertilizers and 100% Urea. The lowest was derived from the application of 100% Urea, 35.61 t ha -1 . Cultivation of eggplant with 3 main branches has resulted better growth and fruit yield than 1 and 2 main branches, 50.85, 47.91 and 30.79 t ha -1 , respectively.

Keywords: eggplant, goat manure, main branch, urea

Agbo, C.U., P.U. Chukwudi and A.N. Ogbu. 2012. Effects of rates and frequency of application of organic manure on gowth, yield and biochemical composition of Solanum melongena L. (cv. ‘Ngwa Local’) Fruits. Journal of Animal and Plant Sciences. 14 (2): 1952-1960.

BPS. 2013. Vegetable production in Indonesia 2009-2013. (in Indonesian).Central Bureau of Statistic and the Directorate General of Horticulture.

Cerny, J., J. Balik, M. Kulhanek, F. Vasak., L. Peklova and O. Sedlar. 2012. The effect of mineral n fertilizer and sewage sludge on yield and nitrogen efficiency of silage maize. Plant Soil Environ. 58 (2): 76-83.

Gandhi and U.S. Sundari. 2012. Effect of vermicompost prepared from aquatic weeds on growth and yield of eggplant (Solanum melongena L.). J. Biofertil Biopesticide. 3 (5): 1-4.

Gardner, F.P., R.B. Pearce and R.L. Mitchell. 1991. Physiology of crops plants. Universitas Indonesia. Jakarta. .(in Indonesian). pp. 355-378

Gulshan, A.B., H.M. Saeed., S. Javidi., T. Meryem., M.I. Atta and M. Aminuddin. 2013. Effects of animal manure on the growth and development of okra (Abelmoschus esculentus L.). Journal of Agricultural and Biological Science. 8 (3): 213-219.

Jagatheeswari, D. 2013. Effect of vermicompost on growth and yield of eggplant (Solanum melongena L.). Indian Streams Research Journal. 3 (4): 1-6.

Jumini and A. Marliah. 2009. Growth and yield of eggplant due to application of leaf fertilizer Gandasil D and Harmonik growth regulators (in Indonesian). J. Floratek. 4 (1): 73-80.

Lakitan, B. 1996. Physiology of plant growth and develpment. (in Indonesian). Grafindo. Persada. Jakarta. p. 217.

Nafiu, A. K., A.O. Togun., M.O. Abiodun and V. O. Chude. 2011. Effects of NPK fertilizer on growth, drymatter production and yield of eggplant in Southwestern Nigeria. Agric. Biol. J. N. Am. 2 (7): 1117-1125.

Palm, C.A., R.J.K. Myers and S.M. Nandwa. 1997. Combined use of organic and inorganic nutrient sources for soil fertility maintenance and replenishment. ASA and SSSA. pp. 193-217.

Raden, I., B.S. Purwoko., Hariadi, M. Ghulamahdi and E. Santosa. 2009. Effect of pruning high and number of primary branches maintained on jatropha oil production (Jatropha curcas L.). (in Indonesian). J. Agron. Indonesia. 37 (2): 159-166.

Ridho, C. and R. Yuliana. 2007. Assessment giving some Saputra nutrition concentration on growth and yield of two varieties of eggplant (Solanum melongena L.). (in Indonesian). Jurnal Pertanian Mapeta. 10 (1): 24 – 30.

Sanchez, A.P. 1976. Properties and management of soil in the tropics. John Wiley and Sons. Inc. New York. p. 618.

Sharma, S.P and J.S. Brar. 2008. Nutritional requirements of brinjal (Solanum melongena L.) - A review. Agric. Rev. 29 (2): 79 – 88.

Sowinska, K.A and M. Krygier. 2013. Yield quantity and quality of field cultivated and the degree of fruit maturity. Acta Sci. Pol. Holturum Cultus. 12 (2): 13-23.

Sutanto, R. 2002. Towards organic farming

as alternative and sustainable agriculture. (in Indonesian). Kanisius. Yogyakarta. p.218.

Suwandi. 2009. Measuring of plant nutrient needs in development of innovation sustainable vegetable cultivation. (in Indonesian). Development of Agricultural Innovation. 2 (2): 133-147.

Taiz, L. and E. Zeiger. 2010. Plant physiology. Fifth Edition. Sinauer Associates Inc., Publishers. Sunderland, Massachusetts, USA. p. 782.

Ullah, M.S., M.S. Islam, M.A. Islam and T. Haque. 2008. Effects of organic manures and chemical fertilizers on the yield of brinjal and soil properties. J. Bangladesh Agril. Univ. 6 (2): 271–276.

Wartapa, A., Y. Effendi and Sukadi. 2009. The impacts of primary branch number arrangement and crop reduction on yield and seed quality of Kaliurang tomato variety (Lycopersicum esculentum Mill). (in Indonesian) Jurnal Ilmu-ilmu Pertanian. 5 (2): 150 – 163.

Waseem, K., A. Hussain., M. S. Jilani., M. Kiran., Ghazanfarullah, S. Javeria and A. Hamid. 2013. Nutritional management in brinjal (Solanum melongena L.) using different growing media. Pakistan Journal of Science. 65 (1): 21-25.

Effect of edible coatings on the postharvest quality of eggplant (solanum aethiopicum l.) Fruits during low temperature storage

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Domestication of Eggplants: A Phenotypic and Genomic Insight

• First Online: 31 May 2019

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• Anna M. L. Page 3 ,
• Marie-Christine Daunay 4 ,
• Xavier Aubriot 5 &
• Mark A. Chapman 3  

Part of the book series: Compendium of Plant Genomes ((CPG))

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Agriculture, and in particular systematic and repeated cultivation of plants, is one of the main characteristics of post-Neolithic sedentary human societies. Deciphering the domestication pathways that have allowed for extensive cultivation of crops is of great scientific importance: first, because it can reveal the patterns and processes of human-induced selection and contribute to the knowledge of the genetic basis of adaptive traits, and second, because identifying the times and locations of domestication is crucial to the understanding of our own evolutionary history, in particular for the last ca. 12,000 years. Finally, the identification of genes involved in domestication could offer potential for future crop improvement. In some instances, knowledge from one crop can be transferred to another to reveal broad patterns, as well as the extent to which parallel evolution has given rise to the crops we rely on today. There have been a number of studies into eggplant domestication, but clarifying the routes and even the number of domestications has until today been limited. This is due to (1) partial knowledge on the identity of eggplant wild relatives, (2) sparse sampling (both in terms of species/accessions and types of data), and (3) inadequacy of the statistical tools used for phylogenetic/demographic inferences. However, the most recent analyses of Solanum melongena point to a single domestication and significant crop-wild-weedy gene flow, which likely hampered earlier phylogenetic attempts. Here, we provide an overview of the current understanding of the domestication frameworks for the three eggplants, Solanum melongena , S. aethiopicum and S. macrocarpon . First, we detail the phenotypical traits of the crops and of their wild progenitors. Then, we detail the historical hypotheses on domestication of eggplants and, when possible, we re-evaluate them in the light of the genomic data generated within the last couple of years.

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Aubriot X, Knapp S, Syfert MM, Poczai P, Buerki S (2018) Shedding new light on the origin and spread of the brinjal eggplant ( Solanum melongena L.) and its relatives. Am J Bot 105(7):1175–1187. https://doi.org/10.1002/ajb2.1133

Article   Google Scholar  

Aubriot X, Singh P, Knapp S (2016) Tropical Asian species show that the old world clade of ‘spiny solanums’ ( Solanum subgenus Leptostemonum pro parte : Solanaceae) is not monophyletic. Bot J Linn Soc 181(2):199–223. https://doi.org/10.1111/boj.12412

Barchi L, Lanteri S, Portis E, Vale G, Volante A, Pulcini L, Ciriaci T, Acciarri N, Barbierato V, Toppino L, Rotino GL (2012) A RAD tag derived marker based eggplant linkage map and the location of QTLs determining anthocyanin pigmentation. PLoS ONE 7(8):e43740. https://doi.org/10.1371/journal.pone.0043740

Article   CAS   PubMed   PubMed Central   Google Scholar  

Barker G (2011) The cost of cultivation. Nature 473:163–164

Article   CAS   Google Scholar  

Bukenya-Ziraba R (2004) Solanum anguivi . In: Grubben GJH, Denton OA (eds) PROTA, plant resources of tropical Africa, vol 2-vegetables. pp 480–482

Google Scholar  

Bukenya-Ziraba R, Bonsu KO (2004) Solanum macrocarpon . In: Grubben GJH, Denton OA (eds) Plants resources of tropical Africa vol 2-vegetables. Backhuys, Leiden, Netherlands, pp 484–488

Bukenya ZR, Carasco JF (1994) Biosystematic study of Solanum macrocarpon — S. dasyphyllum complex in Uganda and relations with Solanum linnaeanum . East African Agric For J 59(3):187–204

Bukenya ZR, Carasco JF (1995) Crossability and cytological studies in Solanum macrocarpon and Solanum linnaeanum (Solanaceae). Euphytica 86(1):5–13. https://doi.org/10.1007/bf00035933

Bukenya ZR, Carasco JF (1999) Ethnobotanical aspects of Solanum L. (Solanaceae) in Uganda. In: Nee M, Symon DE, Lester RN, Jessop JP (eds) Solanaceae IV, advances in biology and utilization. The royal botanic gardens, Kew, pp 345–360

Burke JM, Burger JC, Chapman MA (2007) Crop evolution: from genetics to genomics. Curr Opin Genet Dev 17(6):525–532

Cericola F, Portis E, Toppino L, Barchi L, Acciarri N, Ciriaci T, Sala T, Rotino GL, Lanteri S (2013) The population structure and diversity of eggplant from Asia and the Mediterranean basin. PLoS ONE 8(9). https://doi.org/10.1371/journal.pone.0073702

Chakrabarti M, Zhang N, Sauvage C, Munos S, Blanca J, Canizares J, Jose Diez M, Schneider R, Mazourek M, McClead J, Causse M, van der Knaap E (2013) A cytochrome P450 regulates a domestication trait in cultivated tomato. Proc Natl Acad Sci USA 110(42):17125–17130. https://doi.org/10.1073/pnas.1307313110

Article   CAS   PubMed   Google Scholar  

Cong B, Barrero LS, Tanksley SD (2008) Regulatory change in YABBY-like transcription factor led to evolution of extreme fruit size during tomato domestication. Nat Genet 40(6):800–804. https://doi.org/10.1038/ng.144

Daunay M-C, Lester RN, Ano G (2001a) Eggplant. In: Charrier A, Jacquot M, Hamon S, Nicolas D (eds) Tropical plant breeding. Science Publishers, Montpellier, pp 199–222

Daunay MC (2008) Eggplant. In: Prohens J, Nuez F (eds) Vegetables II: Fabaceae, Liliaceae, Solanaceae, and Umbelliferae. Springer, New York, pp 163–220

Chapter   Google Scholar  

Daunay MC, Aubert S, Frary A, Doganlar S, Lester RN, Barendse G, van der Weerden G, Hennart JW, Haanstra J, Dauphin F, Jullian E (2004) Eggplant ( Solanum melongena ) fruit colour: pigments, measurements and genetics. In: Voorrips RE (ed) Proceedings of the XIIth EUCARPIA meeting on genetics and breeding of Capsicum and eggplant, 17–19 May 2004. Noordwijkerhout, The Netherlands. pp 108–116

Daunay MC, Dalmon A, Lester RN (1999) Management of a collection of Solanum species for eggplant ( Solanum melongena L.) breeding purposes. In: Nee M, Symon DE, Lester RN, Jessop JP (eds) Solanaceae IV: advances in biology and utilization. The Royal Botanic Gardens, Kew, pp 369–383

Daunay MC, Hazra P (2012) Eggplant. In: Peter KV, Hazra P (ed) Handbook of vegetables. Studium Press LLC, pp 258–322

Daunay MC, Lester RN, Ano G (2001b) Eggplant. In: Charrier A, Jacquot M, Hamon S, Nicolas D (ed) Tropical plant breeding. CIRAD and Science Publishers, Inc., pp 199–222

Daunay MC, Lester RN, Laterrot H (1991) The use of wild species for the genetic improvement of Brinjal eggplant ( Solanum melongena ) and tomato ( Lycopersicum esculentum ). In: Hawkes JG, Lester RN, Nee M, Estrada N (eds) Solanaceae III: taxonomy, chemistry, and evolution. Kew: Royal Botanic Gardens. Royal Botanic Gardens, Kew

Davidar P, Snow AA, Rajkumar M, Pasquet R, Daunay MC, Mutegi E (2015) The potential for crop to wild hybridization in eggplant ( Solanum melongena ; Solanaceae) in southern India. Am J Bot 102(1):129–139. https://doi.org/10.3732/ajb.1400404

Article   PubMed   Google Scholar  

Deb DB (1979) Solanaceae in India. In: Hawkes JG, Lester RN, Skelding AD (eds) The biology and taxonomy of the Solanaceae, vol 7 Linnean Society Symposium. Academic Press for the Linnaean Society of London, pp 87–112

Decker DS (1985) Numerical analysis of allozyme variation in Cucurbita pepo . Econ Bot 39(3):300–309. https://doi.org/10.1007/bf02858800

De-Queiroz K (2007) Species concepts and species delimitation. Syst Biol 56(6):879–886

Diamond J (2002) Evolution, consequences and future of plant and animal domestication. Nature 418(6898):700–707

Doebley JF, Goodman MM, Stuber CW (1984) Isoenzymatic variation in Zea (Gramineae). Syst Bot 9:203–218

Doganlar S, Frary A, Daunay MC, Lester RN, Tanksley SD (2002) Conservation of gene function in the Solanaceae as revealed by comparative mapping of domestication traits in eggplant. Genetics 161(4):1713–1726

CAS   PubMed   PubMed Central   Google Scholar  

Frary A, Frary A, Daunay M-C, Huvenaars K, Mank R, Doğanlar S (2014) QTL hotspots in eggplant ( Solanum melongena ) detected with a high resolution map and CIM analysis. Euphytica 197(2):211–228. https://doi.org/10.1007/s10681-013-1060-6

Frary A, Nesbitt TC, Frary A, Grandillo S, van der Knaap E, Cong B, Liu J, Meller J, Elber R, Alpert KB, Tanksley SD (2000) fw2.2 : a quantitative trait locus key to the evolution of tomato fruit size. Science 289:85–88

Fu YB (2015) Understanding crop genetic diversity under modern plant breeding. Theor Appl Genet 128(11):2131–2142

Gramazio P, Prohens J, Plazas M, Mangino G, Herraiz FJ, Vilanova S (2017) Development and genetic characterization of advanced backcross materials and an introgression line population of Solanum incanum in a S. melongena background. Front Plant Sci 8:(1477). https://doi.org/10.3389/fpls.2017.01477

Harris DR (1990) Vavilov’s concept of centres of origin of cultivated plants: its genesis and its influence on the study of agricultural origins. Biol J Linn Soc 39:7–16

Hurtado M, Vilanova S, Plazas M, Gramazio P, Fonseka HH, Fonseka R, Prohens J (2012) Diversity and relationships of eggplants from three geographically distant secondary centers of diversity. Plos One 7(7). https://doi.org/10.1371/journal.pone.0041748

Jayakumar K, Murugan K (2016) Solanum alkaloids and their pharmaceutical roles: a review. J Anal Pharm Res 3(6):00075. https://doi.org/10.15406/japlr.2016.03.00075

Karihaloo JL, Brauner S, Gottlieb LD (1995) Random amplified polymorphic DNA variation in the eggplant, Solanum melongena L. (Solanaceae). Theor Appl Genet 90:767–770

Karihaloo JL, Kaur M, Singh S (2002) Seed protein diversity in Solanum melongena L. and its wild and weedy relatives. Genet Resour Crop Evol 49(6):533–539. https://doi.org/10.1023/a:1021288108928

Karihaloo JL, Rai M (1995) Significance of morphological variability in Solanum insanum L. ( sensu lato ). Plant Genetic Resour Newsl 103 (24–26)

Kaushik P, Gramazio P, Vilanova S, Raigon MD, Prohens J, Plazas M (2017) Phenolics content, fruit flesh colour and browning in cultivated eggplant, wild relatives and interspecific hybrids and implications for fruit quality breeding. Food Res Int 102:392–401. https://doi.org/10.1016/j.foodres.2017.09.028

Khan R (1979) Solanum melongena and its ancestral forms. In: Hawkes JG, Lester RN, Skelding AD (eds) The biology and taxonomy of the Solanaceae. Academic Press for the Linnaean Society of London, pp 629–636

Knapp S (2008) Species concepts and floras: what are species for? Biol J Linn Soc 95(1):17–25

Knapp S, Vorontsova MS, Prohens J (2013) Wild relatives of the eggplant ( Solanum melongena L.: Solanaceae): new understanding of species names in a complex group. PLoS ONE 8(2):e57039. https://doi.org/10.1371/journal.pone.0057039

Larson G, Piperno DR, Allaby RG, Purugganan MD, Andersson L, Arroyo-Kalin M, Barton L, Climer Vigueira C, Denham T, Dobney K, Doust AN, Gepts P, Gilbert MT, Gremillion KJ, Lucas L, Lukens L, Marshall FB, Olsen KM, Pires JC, Richerson PJ, Rubio de Casas R, Sanjur OI, Thomas MG, Fuller DQ (2014) Current perspectives and the future of domestication studies. Proc Natl Acad Sci USA 111(17):6139–6146. https://doi.org/10.1073/pnas.1323964111

Lester RN (1979) The use of protein characters in the taxonomy of Solanum and other Solanaceae In: Hawkes JG, Lester RN, Skelding AD (eds) The biology and taxonomy of the Solanaceae. Academic Press for the Linnaean Society of London, pp 285–303

Lester RN (1986) Taxonomy of scarlet eggplants, Solanum aethiopicum L. Acta Hort 182:125–132

Lester RN (1989) Evolution under domestication involving disturbance of genic balance. Euphytica 44:125–132

Lester RN, Daunay MC (2003) Diversity of African vegetable Solanum species and its implications for a better understanding of plant domestication. In: Knüpffer H, Ochsmann J (eds) Rudolf Mansfeld and plant genetic resources, vol 22. Schriften zu genetischen Ressourcen (Informationszentrum biologische Vielfalt), Gatersleben (Germany), pp 137–152

Lester RN, Hakiza JJH, Stavropoulos N, Teixiera MM (1986) Variation patterns in the African scarlet eggplant Solanum aethiopicum L. In: Styles BT (ed) Infraspecific classification of wild and cultivated plants. Oxford University Press, pp 283–307

Lester RN, Hasan SMZ (1991) Origin and domestication of the brinjal eggplant, Solanum melongena , from S. incanum in Africa and Asia. In: Hawkes JG, Lester RN, Nee M, Estrada N (eds) Solanaceae III: taxonomy, chemistry, evolution. Royal Botanic Gardens, UK, Kew, pp 369–387

Lester RN, Hawkes JG (2001) Solanaceae. In: Hanelt P (ed) Mansfeld’s Encyclopedia of agricultural and horticultural crops, vol 4. Springer, Berlin, pp 1790–1856

Lester RN, Jaeger PML, Bleijendaal-Spierings BHM, Bleijendaal HPO, Holloway HLO (1990) African eggplants—a review of collecting in West Africa. Plant Genetic Resour Newsl 81(82):17–26

Lester RN, Niakan L (1986) Origin and domestication of the scarlet eggplant, Solanum aethiopicum , from S. anguivi in Africa In: D’Arcy WG (ed) Solanaceae, biology and systematics. Columbia University Press, pp 433–456

Lester RN, Seck A (2004) Solanum aethiopicum L. In: Grubben GJH, Denton OA (eds) PROTA, plant resources of tropical Africa, vol PROTA 2. Vegetables. Backhuys, Leiden, The Netherlands, pp 472–477

Lester RN, Thitai GNW (1989) Inheritance in Solanum aethiopicum , the scarlet eggplant. Euphytica 40(1–2):67–74

Liu JP, Van Eck J, Cong B, Tanksley SD (2002) A new class of regulatory genes underlying the cause of pear-shaped tomato fruit. Proc Natl Acad Sci USA 99(20):13302–13306. https://doi.org/10.1073/pnas.162485999

Luckow M (1995) Species concepts—assumptions, methods, and applications. Syst Bot 20(4):589–605. https://doi.org/10.2307/2419812

Mace ES, Lester RN, Gebhardt CG (1999) AFLP analysis of genetic relationships among the cultivated eggplant, Solanum melongena L., and wild relatives (Solanaceae). Theor Appl Genet 99(3):626–633. https://doi.org/10.1007/s001220051277

Mallet J (1995) A species definition for the modern synthesis. Trends Ecol Evol 10(7):294–299

Matu EN (2008) Solanum incanum L. In: Schmelzer GH, Gurib-Fakim A (eds) PROTA. Plant resources of tropical Africa, vol 11-medicinal plants. Wageningen, The Netherlands

McLeod MJ, Guttman SI, Eshbaugh WH, Rayle RE (1983) An electrophoretic study of evolution in Capsicum (Solanaceae). Evolution 37(3):562–574. https://doi.org/10.1111/j.1558-5646.1983.tb05573.x

Meyer RS, Bamshad M, Fuller DQ, Litt A (2014) Comparing medicinal uses of eggplant and related Solanaceae in China, India, and the Philippines suggests the independent development of uses, cultural diffusion, and recent species substitutions. Econ Bot 68(2):137–152. https://doi.org/10.1007/s12231-014-9267-6

Meyer RS, DuVal AE, Jensen HR (2012a) Patterns and processes in crop domestication: an historical review and quantitative analysis of 203 global food crops. New Phytol 196(1):29–48. https://doi.org/10.1111/j.1469-8137.2012.04253.x

Meyer RS, Karol KG, Little DP, Nee MH, Litt A (2012b) Phylogeographic relationships among Asian eggplants and new perspectives on eggplant domestication. Mol Phylogen Evol 63:685–701

Meyer RS, Whitaker BD, Little DP, Wu S-B, Kennelly EJ, Long C-L, Litt A (2015) Parallel reductions in phenolic constituents resulting from the domestication of eggplant. Phytochemistry 115:194–206. https://doi.org/10.1016/j.phytochem.2015.02.006

Mutegi E, Snow AA, Rajkumar M, Pasquet R, Ponniah H, Daunay M-C, Davidar P (2015) Genetic diversity and population structure of wild/weedy eggplant ( Solanum insanum , Solanaceae) in southern India: implications for conservation. Am J Bot 102(1):140–148. https://doi.org/10.3732/ajb.1400403

N’Gbesso MFDP, Kouassi A, Fondio L, Andé Djidji H (2016) Etude de la diversité intra et interspécifique des caractères phénotypiques chez deux espèces d’aubergines africaines: Solanum macrocarpon L. et Solanum dasyphyllum L. Int J Biol Chem Sci 10(4):1793

Naegele RP, Boyle S, Quesada-Ocampo LM, Hausbeck MK (2014) Genetic diversity, population structure, and resistance to Phytophthora capsici of a worldwide collection of eggplant germplasm. Plos One 9(5). https://doi.org/10.1371/journal.pone.0095930

Padmini K, Yogeesha HS, Naik LB (2008) Genetics of fresh seed dormancy in brinjal ( Solanum melongena ). Indian J Agric Sci 78(4):304–307

Plazas M, Vilanova S, Gramazio P, Rodriguez-Burruezo A, Fita A, Herraiz FJ, Ranil R, Fonseka R, Niran L, Fonseka H, Kouassi B, Kouassi A, Prohens J (2016) Interspecific hybridization between eggplant and wild relatives from different genepools. J Am Soc Hort Sci 141(1):34–44

Portis E, Barchi L, Toppino L, Lanteri S, Acciarri N, Felicioni N, Fusari F, Barbierato V, Cericola F, Valè G, Rotino GL (2014) QTL mapping in eggplant reveals clusters of yield-related loci and orthology with the tomato genome. PLoS ONE 9(2):e89499. https://doi.org/10.1371/journal.pone.0089499

Prohens J, Whitaker BD, Plazas M, Vilanova S, Hurtado M, Blasco M, Gramazio P, Stommel JR (2013) Genetic diversity in morphological characters and phenolic acids content resulting from an interspecific cross between eggplant, Solanum melongena, and its wild ancestor (S. incanum). Ann Appl Biol 162(2):242–257. https://doi.org/10.1111/aab.12017

Ranil RHG, Prohens J, Aubriot X, Niran HML, Plazas M, Fonseka RM, Vilanova S, Fonseka HH, Gramazio P, Knapp S (2017) Solanum insanum L. (subgenus Leptostemonum Bitter, Solanaceae), the neglected wild progenitor of eggplant ( S. melongena L.): a review of taxonomy, characteristics and uses aimed at its enhancement for improved eggplant breeding. Genet Resour Crop Evol 64(7):1707–1722. https://doi.org/10.1007/s10722-016-0467-z

Sakata Y, Lester RN (1994) Chloroplast DNA diversity in eggplant ( Solanum melongena ) and its related species S. incanum and S. marginatum . Euphytica 80(1–2):1–4

Sakata Y, Lester RN (1997) Chloroplast DNA diversity in brinjal eggplant ( Solanum melongena L.) and related species. Euphytica 97(3):295. https://doi.org/10.1023/a:1003000612441

Salgon S, Jourda C, Sauvage C, Daunay M-C, Reynaud B, Wicker E, Dintinger J (2017) Eggplant resistance to the Ralstonia solanacearum species complex involves both broad-spectrum and strain-specific quantitative trait loci. Front Plant Sci 8:828

Sauvage C, Rau A, Aichholz C, Chadoeuf J, Sarah G, Ruiz M, Santoni S, Causse M, David J, Glémin S (2017) Domestication rewired gene expression and nucleotide diversity patterns in tomato. Plant J 91(4):631–645. https://doi.org/10.1111/tpj.13592

Schippers RR (2002) African indigenous vegetables. In: Natural resources international Ltd hds (ed) An overview of the cultivated species

Seck A, Sow A (1994) Suppression par voie génétique de la dormance des semences de jaxatu ( Solanum aethiopicum L.). RADHORT (FAO), Bulletin de liaison 7:12p

Singh AK, Singh M, Singh R, Kumar S, Kalloo G (2006) Genetic diversity within the genus Solanum (Solanaceae) as revealed by RAPD markers. Curr Sci 90(5):711–716

CAS   Google Scholar  

Smykal P, Nelson MN, Berger JD, von Wettberg EJB (2018) The impact of genetic changes during crop domestication. Agron-Basel 8(7). https://doi.org/10.3390/agronomy8070119

Toppino L, Barchi L, Lo Scalzo R, Palazzolo E, Francese G, Fibiani M, D’Alessandro A, Papa V, Laudicina VA, Sabatino L, Pulcini L, Sala T, Acciarri N, Portis E, Lanteri S, Mennella G, Rotino GL (2016) Mapping quantitative trait loci affecting biochemical and morphological fruit properties in eggplant ( Solanum melongena L.). Front Plant Sci 7:256. https://doi.org/10.3389/fpls.2016.00256

Tümbilen Y, Frary A, Daunay MC, Doganlar S (2011) Application of EST-SSRs to examine genetic diversity in eggplant and its close relatives. Turk J Biol 35(2):125–136. https://doi.org/10.3906/biy-0906-57

Turland NJ, Wiersema JH, Barrie FR, Greuter W, Hawksworth DL, Herendeen PS, Knapp S, Kusber W-H, Li D-Z, Marhold K, May TW, McNeill J, Monro AM, Prado J, Price MJ, Smith GF (eds) 2018: international code of nomenclature for algae, fungi, and plants (Shenzhen code) adopted by the Nineteenth International Botanical Congress Shenzhen, China, July 2017. Regnum vegetable 159. Koeltz Botanical Books, Glashütten. https://doi.org/10.12705/Code.2018

Vavilov NI (1926) Studies on the origin of cultivated plants. Institut Botanique Appliqué et d’Amélioration des Plantes. State Press, Leningrad, USSR

Vavilov NI (ed) (1935) Origin and geography of cultivated plants, vol 1. English Translation, 1994 edn

Vilanova S, Manzur JP, Prohens J (2012) Development and characterization of genomic simple sequence repeat markers in eggplant and their application to the study of diversity and relationships in a collection of different cultivar types and origins. Mol Breed 30(2):647–660. https://doi.org/10.1007/s11032-011-9650-2

Vorontsova MS, Knapp S (eds) (2016) A revision of the “spiny solanums”, Solanum subgenus Leptostemonum (Solanaceae), in Africa and Madagascar, vol 99. Systematic botany monographs. The American society of plant taxonomists

Vorontsova MS, Stern S, Bohs L, Knapp S (2013) African spiny Solanum (subgenus Leptostemonum , Solanaceae): a thorny phylogenetic tangle. Bot J Linn Soc 173(2):176–193. https://doi.org/10.1111/boj.12053

Wang JX, Gao TG, Knapp S (2008) Ancient Chinese literature reveals pathways of eggplant domestication. Ann Bot 102(6):891–897. https://doi.org/10.1093/aob/mcn179

Article   PubMed   PubMed Central   Google Scholar  

Weese TL, Bohs L (2010) Eggplant origins: out of Africa, into the Orient. Taxon 59:49–56

Wu SB, Meyer RS, Whitaker BD, Litt A, Kennelly EJ (2013) A new liquid chromatography-mass spectrometry-based strategy to integrate chemistry, morphology, and evolution of eggplant ( Solanum ) species. J Chromatogr 1314:154–172. https://doi.org/10.1016/j.chroma.2013.09.017

Xiao H, Jiang N, Schaffner E, Stockinger EJ, van der Knaap E (2008) A retrotransposon-mediated gene duplication underlies morphological variation of tomato fruit. Science 319(5869):1527–1530

Yogeesha HS, Upreti KK, Padmini K, Bhanuprakash K, Murti GSR (2006) Mechanism of seed dormancy in eggplant ( Solanum melongena L.). Seed Sci Technol 34(2):319–325. https://doi.org/10.15258/sst.2006.34.2.07

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Page, A.M.L., Daunay, MC., Aubriot, X., Chapman, M.A. (2019). Domestication of Eggplants: A Phenotypic and Genomic Insight. In: Chapman, M. (eds) The Eggplant Genome. Compendium of Plant Genomes. Springer, Cham. https://doi.org/10.1007/978-3-319-99208-2_12

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Field Performance of Bt Eggplants ( Solanum melongena L.) in the Philippines: Cry1Ac Expression and Control of the Eggplant Fruit and Shoot Borer ( Leucinodes orbonalis Guenée)

Desiree m. hautea.

1 Institute of Plant Breeding/CSC, College of Agriculture, University of the Philippines Los Baños, College, Laguna, 4031, Philippines

Lourdes D. Taylo

Anna pauleen l. masanga, maria luz j. sison, josefina o. narciso, reynaldo b. quilloy, randy a. hautea.

2 International Service for the Acquisition of Agri-Biotech Applications, Los Baños, Laguna, 4030, Philippines

Frank A. Shotkoski

3 International Programs, Cornell University, Ithaca, New York, 14853, United States of America

Anthony M. Shelton

4 Department of Entomology, Cornell/NYSAES, Geneva, New York, 14456, United States of America

Conceived and designed the experiments: DMH RAH JON LDT MLJS FAS AMS. Performed the experiments: JON RBQ LDT MLJS APLM DMH RAH. Analyzed the data: LDT APLM DMH RAH. Wrote the paper: DMH LDT APLM RAH FAS AMS. Developed the breeding materials: JON LDT RBQ DMH RAH. Supervised the field trials: DMH RAH RBQ LDT FAS. Prepared application and obtained all relevant permits for confined field trials: DMH JON LDT RAH.

Associated Data

Data are available from Dryad (doi: 10.5061/dryad.ks131 ).

Plants expressing Cry proteins from the bacterium, Bacillus thuringiensis (Bt), have become a major tactic for controlling insect pests in maize and cotton globally. However, there are few Bt vegetable crops. Eggplant ( Solanum melongena ) is a popular vegetable grown throughout Asia that is heavily treated with insecticides to control the eggplant fruit and shoot borer, Leucinodes orbonalis (EFSB). Herein we provide the first publicly available data on field performance in Asia of eggplant engineered to produce the Cry1Ac protein. Replicated field trials with five Bt eggplant open-pollinated (OP) lines from transformation event EE-1 and their non-Bt comparators were conducted over three cropping seasons in the Philippines from 2010–2012. Field trials documented levels of Cry1Ac protein expressed in plants and evaluated their efficacy against the primary target pest, EFSB. Cry1Ac concentrations ranged from 0.75–24.7 ppm dry weight with the highest in the terminal leaves (or shoots) and the lowest in the roots. Cry1Ac levels significantly increased from the vegetative to the reproductive stage. Bt eggplant lines demonstrated excellent control of EFSB. Pairwise analysis of means detected highly significant differences between Bt eggplant lines and their non-Bt comparators for all field efficacy parameters tested. Bt eggplant lines demonstrated high levels of control of EFSB shoot damage (98.6–100%) and fruit damage (98.1–99.7%) and reduced EFSB larval infestation (95.8–99.3%) under the most severe pest pressure during trial 2. Moths that emerged from larvae collected from Bt plants in the field and reared in their Bt eggplant hosts did not produce viable eggs or offspring. These results demonstrate that Bt eggplant lines containing Cry1Ac event EE-1 provide outstanding control of EFSB and can dramatically reduce the need for conventional insecticides.

Introduction

Since their introduction in 1996, maize and cotton expressing insecticidal proteins derived from the soil bacterium Bacillus thuringiensis (Bt) have been widely adopted and in 2014 were planted on 78.8 million ha in 28 countries predominantly by resource-poor farmers [ 1 ]. Bt crops are another form of host plant resistance, the foundation for integrated pest management (IPM) programs [ 2 ]. Several major maize and cotton pests have been successfully controlled, and insecticide use on them has been substantially reduced throughout most adopting countries [ 3 ]. Unfortunately, the development of Bt crops has been limited to major commodity crops (maize, cotton, and soybean) and not fruit and vegetables, except sweet corn. This situation is especially unfortunate since fruit and vegetables, when taken together, receive more insecticides than maize, cotton and rice combined [ 4 ].

Eggplant, Solanum melongena L. (also known as brinjal and aubergine) is one of the most important, inexpensive and popular vegetable crops grown and consumed in Asia. In the Philippines, eggplant production accounts for more than 30.0% of the total volume of production of the most important vegetables in the country [ 5 ]. Eggplant production provides an important source of cash income, particularly for small, resource-poor farmers. The biggest constraint to eggplant production throughout Asia is the chronic and widespread infestation by the eggplant fruit-and-shoot borer (EFSB), Leucinodes orbonalis Guenée [ 6 ]. The larvae damage eggplant by boring into the petiole and midrib of leaves and tender shoots resulting in wilting and desiccation of stems. Flowers are also fed upon resulting in flower drop or misshapen fruits. The most serious economic damage caused by EFSB is to the fruit by producing holes, feeding tunnels and frass (or larval excrement) that make the fruit unmarketable and unfit for human consumption. At high pest pressure, EFSB damage in the Philippines results in yield loss of up to 80.0% of the crop [ 7 ]. Surveys of eggplant farmers in the major eggplant growing provinces of the Philippines [ 7 – 11 ] revealed that almost all of them use chemical insecticides to control EFSB because other control measures such as manual removal of EFSB-damaged fruits and wilted shoots, use of biological control arthropods and pheromone traps [ 12 ] have proven ineffective, impractical and expensive. Eggplant farmers in the Philippines employ frequent applications (20–72 times for 5–6 months/season) of mixtures of insecticides to control EFSB, which increase production costs and pose risks to human health and the environment. Studies conducted in Sta. Maria, Pangasinan [ 8 , 13 , 14 ] showed frequent use of broad-spectrum insecticides including profenofos, triazophos, chlorpyrifos, cypermethrin, and malathion. Residues of these insecticides were detected in the soil of eggplant farms and in harvested fruits [ 14 ]. Farmers and farm workers in the study attributed various ailments such as skin irritation, redness of the eyes, muscle pains and headaches to exposure to these pesticides.

After more than 40 years, conventional breeding has not produced any commercial variety of eggplant conferring high level of resistance to the EFSB [ 15 ]. Therefore, efforts became focused on developing Bt eggplant that expresses the same Cry1Ac protein as the cotton event MON531, which has been approved by regulatory agencies in many countries [ 16 – 18 ]. MON531 has been bred into cotton varieties that have been on the global market for almost 20 years with no verifiable report of any adverse effect on human health or the environment. The modified gene used in MON531 encodes an amino acid sequence that is 99.4% identical to the naturally occurring microbial Cry1Ac protein [ 19 , 20 ].

Maharashtra Hybrid Seeds Co. Pvt. Ltd. (Mahyco) inserted the cry1Ac gene under the control of the constitutive 35S CaMV promoter into eggplant to control feeding damage caused by EFSB [ 21 ]. The transformation event designated as 'EE-1' was introgressed into eggplant varieties and hybrids in India, Bangladesh and the Philippines [ 22 , 23 ]. In 2009, although the Indian biosafety regulatory agency gave biosafety approval to Mahyco event EE-1, the Ministry of the Environment and Forests placed a moratorium on its cultivation in India [ 24 ] that remains in effect as of May 2016. In 2013, four Bt eggplant varieties containing the same EE-1 event were conditionally approved for cultivation in Bangladesh. These were grown on 20 fields in 2014 and the number increased to 108 farms in 2015 ( https://bteggplant.wordpress.com/2015/08/11/speech-by-dr-md-rafiqul-islam-mondal-director-general-bari/ ). In the Philippines, event EE-1 was introgressed into selected EFSB-susceptible eggplant open-pollinated (OP) varieties through conventional backcrossing coupled with diagnostic EE-1 event-specific PCR and a cry1Ac gene strip assay [ 25 ]. Five promising advanced Bt OP lines, developed by the University of the Philippines Los Baños, were selected for Confined Field Trial testing in selected eggplant growing areas of the country.

The studies presented in this report contain the first data on Bt eggplant for control of EFSB in Asia to be submitted to a peer-reviewed journal. The studies were conducted with the following objectives: (1) to determine the expression levels of Cry1Ac protein in Bt eggplant OP lines; and (2) to evaluate the field efficacy of the EE-1 event in Bt eggplant OP lines against field populations of EFSB. Results of these studies will be used to generate crucial information for selecting the best EFSB-resistant Bt eggplant OP lines for market release in the Philippines.

Bt Cry1Ac protein expression in different plant parts in Bt Eggplant OP lines

Significant differences were detected in Cry1Ac protein expression among the different plant parts in all Bt eggplant OP lines grown for two seasons ( Fig 1 , S1 Table ). The highest levels of Cry1Ac protein were detected in the terminal leaves, with decreasing levels of expression in the flowers, fruits, stem and roots. Results of the gene strip test of the non-Bt eggplant comparators (near-isoline counterparts and check) were negative and the quantitative ELISA values were below the limit of quantitation (LOQ = 0.125) of the assay used.

Mean ± SEM Cry1Ac protein concentration in terminal leaves, flowers, fruits, stem, and roots of five (5) Bt eggplant OP lines. n = 4 per plant part/Bt line with 5–10 sample plants per replicate plot. Confined field trial1 (wet/off season) and trial 2 (dry season), CY 2010–2011, Pangasinan, Philippines.

Terminal Leaves

The Cry1Ac protein expressed in terminal leaves ranged from 18.32–24.87 ppm dry weight (DW) in trial 1, and 20.40–21.83 ppm DW in trial 2. Line M4 expressed significantly less Cry1Ac protein than line D2 in trial 1; however there were no other significant differences in expression levels among the Bt eggplant lines in either trial.

There were no significant differences detected in Cry1Ac protein content among the Bt eggplant lines in both trials. Cry1Ac protein content in the flowers ranged from 10.17–16.33 ppm DW in trial 1, and from 14.34–17.57 ppm DW in trial 2.

Fruits (flesh and skin)

There were no significant differences in Cry1Ac protein expression in either the fruit flesh or the skin among the Bt eggplant lines tested in both trials. However, the widest range of variation was observed between the two trials. In trial 1, the fruit flesh contained higher levels of Cry1Ac protein at 9.00–16.23 ppm DW and the fruit skin ranged from 8.82–13.42 ppm DW, but much lower levels of Cry1Ac protein were detected in both the flesh and skin in trial 2 (3.02–9.47 and 2.61–7.18 ppm DW, respectively).

There were no significant differences in Cry1Ac protein expression in the stem among all Bt eggplant lines tested. The stem contained Cry1Ac protein concentration of 2.75–5.22 ppm DW in trial 1 and 5.00–7.02 ppm DW in trial 2.

The roots contained the lowest levels of Cry1Ac protein. The mean Cry1Ac protein concentration (1.8 ppm DW) was similar in both trials. There were no significant differences in Cry1Ac protein expression in the roots among the Bt eggplant lines tested. The highest level of Cry1Ac protein expressed in the roots was 2.64 ppm DW.

Cry1Ac protein expression in terminal leaves at different growth stages in Bt Eggplant OP lines

Significant differences in Cry1Ac protein expression were detected in terminal leaves across three growth stages of eggplant development in all Bt eggplant OP lines in both trials ( Fig 2 , S2 Table ). The observed pattern of Cry1Ac protein expression generally increased from the vegetative stage to the reproductive stage; then at the late reproductive stage the levels slightly decreased in trial 1 but increased in trial 2. Higher concentrations of Cry1Ac protein were detected in trial 2 at the vegetative stage (18.69–19.22 ppm DW) and late reproductive stage (22.32–23.54 ppm DW) compared with amounts detected at the same growth stages during trial 1. Significant differences were observed among the Bt eggplant lines in the amount of Cry1Ac protein expressed during the vegetative and reproductive stages in trial 1. Bt eggplant line M4 showed the lowest level of Cry1Ac protein expression among the lines tested. However, no significant differences were observed among the Bt eggplant lines at all growth stages in trial 2.

Mean ± SEM Cry1Ac protein concentration in the terminal leaves of 5 Bt eggplant OP lines at the vegetative, reproductive and late reproductive stages. n = 4 per growth stage/line with 5–10 plants per replicate plot. Confined field trial 1 (wet/off season) and trial 2 (dry season), CY 2010–2011, Pangasinan, Philippines.

Control of EFSB by Bt Eggplant OP lines

Under natural field infestations, the efficacy against EFSB of Bt eggplant lines and the non-Bt comparators (near-isoline counterparts and check variety) were evaluated for three seasons (trials 1–3) based on the following parameters: % EFSB-damaged shoots, % EFSB-damaged fruits and number of EFSB larvae in fruits. Throughout the sampling/harvest periods, Bt eggplant lines consistently demonstrated a lower percentage of EFSB-damaged shoots ( Fig 3 , S3 Table ), % EFSB- damaged fruits ( Fig 4 , S4A to S4C Table ) and number of EFSB larvae in fruits ( Fig 5 , S4A to S4C Table ) compared to the conventionally-bred non-Bt eggplant comparators.

Mean ± SEM percentage (%) EFSB-damaged shoots in Bt lines and their non-Bt eggplant comparators at different sampling periods. n = 4 per entry with 16 plants per replicate plot. Confined field trials 1 and 3 (wet/off season) and trial 2 (dry season), CY 2010–2012, Pangasinan, Philippines.

Mean ± SEM percentage (%) EFSB-damaged fruits in Bt lines and their non-Bt eggplant comparators at different harvest periods. n = 4 per entry with 16 plants per replicate plot. Confined field trials 1 and 3 (wet/off season) and trial 2 (dry season), CY 2010–2012, Pangasinan, Philippines.

Mean ± SEM number of EFSB larvae in damaged fruits of Bt lines and their non-Bt eggplant comparators at different harvest periods. n = 4 per entry with 16 plants per replicate plot. Confined field trials 1 and 3 (wet/off season) and trial 2 (dry season), CY 2010–2012, Pangasinan, Philippines.

Significant differences among entries ( P = <0 . 0001 ) were detected in all parameters measured in the three trials. Results of paired mean comparison by contrast for all parameters and corresponding level of control (% efficacy) relative to non-Bt eggplant are presented in Table 1 . Highly significant differences were consistently detected between Bt eggplant lines and their corresponding non-Bt eggplant comparators for all parameters in every trial. Comparisons between Bt eggplant lines and non-Bt eggplant comparators showed significantly lower shoot and fruit damage and fewer surviving EFSB larvae in fruits in the Bt eggplant lines tested. Bt eggplant demonstrated 97.7–100% and 96.0–100% control of EFSB shoot and fruit damage, respectively, except in Bt line M4 in trial 1. This line had slightly lower % efficacy for shoot damage (95.3%) and fruit damage (94.1%) but these levels were significanly much better than any of the the non-Bt comparators. Control of EFSB larval infestation in Bt eggplant lines ranged from 88.4–100%, with most lines showing > 96.0% control, except for Bt M1 and M8 in trial 1. Nevertheless, the levels of control of EFSB larval infestation in M1 and M8 were still far better compared to any of the non-Bt comparators tested.

1 Mean comparison by contrast (PROC MIXED in SAS);

** highly significant at 1% probability level; mean of 4 replicates;

2 Bt = eggplant containing event ‘EE-1’; NBt = non-Bt eggplant near-isolines and commercial check;

3 Mean of 10 weekly observation periods;

4 Mean of total harvest periods: Trial 1 (9 harvests); Trial 2 (13 harvests); Trial 3 (9 harvests)

5 Mean of total harvest periods: Trial 1 (9 harvests); Trial 2 (13 harvests); Trial 3 (9 harvests)

6 %Efficacy = (1-Bt/non-Bt) x 100

Seasonal variation in field damage was also observed between Bt eggplant lines and their non-Bt comparators ( Table 1 ). Trials 1 and 3 were conducted during the wet/off planting season when most of the surrounding annual crop was rice. Trial 2 was conducted during the dry season, when eggplants are more widely grown in Pangasinan. Of the three trials conducted, the highest pest pressure was recorded during trial 2 as evidenced by the highest percentages of plant damage and number of insects observed. During trial 2, the highest mean % EFSB-damaged shoots (41.58%), % EFSB-damaged fruits (93.08%), and number of surviving EFSB larvae (16.15 larvae/plot/harvest) were recorded in the non-Bt eggplant comparators. Under such severe pest pressure, the Bt eggplant lines showed <1% EFSB shoot damage, <2% fruit damage and fewer EFSB larvae (<1 larva/plot/harvest).

Survival and Fecundity of EFSB in Bt Eggplant OP lines

EFSB larvae were collected from plants of Bt eggplant lines and non-Bt comparators and brought to the Entomology laboratory and reared continuously in their respective hosts. The results showed that very few EFSB larvae were collected in all Bt eggplant compared with the non-Bt eggplant plants sampled ( Table 2 ). Of the total (27) EFSB larvae reared from Bt eggplant plants, less than half (11/27) emerged as adults and almost half (5/11) of the moths were weak and died before mating. Only six adults were able to mate successfully. However, no viable eggs and offspring resulted from any paired matings involving either male or female EFSB adults collected and reared in the Bt eggplants ( Table 3 ). In contrast, a high percentage (97.3%) of EFSB larvae collected from the non-Bt plants successfully emerged as adults, mated and produced many viable eggs and young larvae.

1 EFSB larvae collected from Bt and non-Bt hosts from larvae collected from trial 2 in Pangasinan and reared continuously on respective hosts in the IPB Entomology P2 Laboratory

2 Bt = eggplant containing event EE-1; NBt = non-Bt eggplant counterpart genotypes

3 Total larval counts collected in 5 Bt OP lines and 2 non-Bt counterparts; 4 reps and 7 harvests

4 Mean of 5 Bt OP lines and 2 non-Bt OP counterpart lines; 4 reps and 7 harvests

5 Relative % = (Total Bt)/(Total (Bt + Non-Bt)) x 100; (Total Non-Bt)/(Total (Bt + Non-Bt)) x 100

1 Bt = eggplant containing event EE-1; NBt = non-Bt eggplant counterpart genotypes

2 Paired matings included all surviving adults collected from Bt hosts reared continuously on same hosts; paired mating of the control were representative samples of surviving adults collected from non-Bt hosts reared continuously on the same host

Spatio-Temporal Expression of Cry1Ac Protein in Bt Eggplant Lines

Recent reviews [ 18 , 26 , 27 ] of Bt crops engineered to express δ-endotoxin proteins cited numerous reports indicating that the expression of Cry proteins vary with plant parts, plant age, genotypes and environmental conditions. To provide the greatest benefits, Cry proteins should be expressed in sufficient quantities to provide high levels of protection to appropriate plant parts and at the stage of growth when the target insect pest pressure is most severe. In this study, significant differences were detected in the amount of Cry1Ac expressed in different plant parts: terminal leaves > flowers > fruits > stem > roots. Cry1Ac expression in the pollen was below the limit of quantitation (LOQ) of the assay used (LOQ = 0.125) (unpublished greenhouse data). It is noteworthy that higher amounts were detected in plant parts preferably attacked by the primary target pest, EFSB. The level of expression of Cry1Ac in Bt eggplant lines tested varied between 0.75±0.33 to 24.87±0.56 ppm DW. These findings are consistent with previous studies conducted in the Philippines [ 25 ] and India [ 21 , 28 ] showing that Bt eggplants have higher levels of Cry1Ac protein expressed in the terminal leaves, flowers and fruits than in the stem and roots. Similarly, a number of studies conducted in other countries also reported variability in Cry protein expression in plant parts in other Bt crops including cotton [ 29 – 31 ], corn [ 32 – 34 ] and rice [ 35 ].

Many researchers have also reported variation in Cry1Ac protein expression in Bt cotton during the growth and development of the plant [ 36 – 42 ]. In Bt cotton, Cry1Ac protein levels were generally high at early stages and then declined as the plant grew to maturity [ 31 , 43 ]. In this study, seasonal variation was also detected in the level of Cry1Ac protein expression in the terminal leaves of Bt eggplant lines. However, the amount of Cry1Ac protein expressed varied only up to 1.7-fold throughout the growing season of 120 days required for profitable eggplant production. Contrary to the results in Bt cotton, in this study the level of Cry1Ac protein expression significantly increased from the vegetative stage to the reproductive stage and either slightly declined or increased at the late reproductive stage depending on the trial. It is important to note that the amount of Cry1Ac protein expressed in Bt eggplant OP lines peaked during the fruit-bearing stage and remained high with the average at 20–23 ppm DW as EFSB pest pressure became more severe.

Factors Affecting Variability in Cry1Ac Protein Expression in Bt Eggplant Lines

Data from other crops also suggest that factors inherent to the variety and the environment affect the variability of Cry1Ac expression. These factors include among others, transgene promoter, parental background, and environmental stressors such as high temperature, heavy drought, waterlogging, and insect damage [ 38 , 44 , 45 ]. In this study, variability in Cry1Ac protein expression in the Bt eggplant lines could also be attributed to using the constitutive 35S CaMV promoter in the EE-1 gene construct, as suggested in studies with Bt cotton which used the same promoter. Parental background has also been reported to affect Cry1Ac protein variability in Bt cotton [ 30 , 31 ]. In this study, the parental background (‘Mara’ and ‘DLP’) of the Bt eggplant OP lines may have influenced, but only to a limited extent, the spatio-temporal variability in Cry1Ac expression. Finally, environmental factors could have contributed to the spatio-temporal expression of the Cry1Ac protein in Bt eggplant lines. Results showed that the levels of Cry1Ac detected during the entire growing season during trial 2 were different compared to results from trial 1. Trial 1 was conducted during the off-season eggplant planting, while trial 2 was conducted during the regular dry season planting. During trial 2, there were more eggplant planted, hence the level of EFSB pest pressure was higher during this season resulting in more damage as shown in the field efficacy data. Weather data obtained during the duration of the two trials indicated that the average daily temperature was similar but the amount of rainfall was much higher in trial 1 than trial 2. A previous report [ 46 ] suggested that environmental factors such as temperature and insect damage could influence expression of a Cry protein.

Variation in Cry1Ac Protein Expression and its Effects on Field Efficacy of Bt Eggplant Lines

It has been a key concern for developers of Bt crops whether variation in Cry protein expression may cause variation in control of the target insect pest. A number of studies in Bt cotton showed that concentration of Cry1Ac correlates well with the efficacy against the target insect pests and that, as the amount of Cry1Ac declines when the crop matures, there is a concomitant decrease in % mortality of the target pest, bollworm ( Helicoverpa armigera or Helicoverpa zea ) [ 29 , 37 , 39 , 47 – 49 ]. In this study, the highest concentration of Cry1Ac protein was expressed in the terminal leaves (24.87± 0.56 ppm DW) and remained high as the Bt eggplant crop matured. The field efficacy of Bt eggplant lines, measured as % EFSB-damaged shoots, also remained very high (95.4–100% reduction) during the entire 10 weeks of evaluation. These results suggest that the high level of expression of Cry1Ac protein results in high field efficacy in Bt eggplant lines. The reduced EFSB-damaged shoots indicate that the effective control of EFSB starting at the vegetative stage will help reduce the field population of EFSB during the fruit-bearing stage resulting in much reduced EFSB damage. Among the plant parts, the level of Cry1Ac protein expressed in the fruits (flesh and skin) was intermediate (2.61±0.36–12.52±3.41 ppm DW). Nevertheless, the % EFSB-damaged fruits in Bt eggplants were effectively reduced (94.1–100% control) throughout the reproductive period of the plants. It should be noted that the lowest concentrations of Cry1Ac detected in the shoots (18.32±2.45 ppm DW) and fruits (2.61±0.36 ppm DW) in the Bt eggplant lines were well above the baseline susceptibility benchmark values of L . orbonalis for Cry1Ac previously reported from India. The average moult inhibitory concentration, MIC 95 , from 29 L . orbonalis populations tested for Cry1Ac was 0.059 ppm [ 21 , 28 ]. More recent work reported the baseline limits for MIC 50 = 0.003 to 0.014 ppm and MIC 95 = 0.028 to 0.145 ppm [ 50 ]. The median lethal concentrations reported were LC 50 = 0.020 and 0.042 ppm [ 50 ] and LC 50 = 0.0326 to 0.0369 mg/mL and LC 90 = 0.0458 to 0.0483 mg/mL of diet [ 51 ]. MIC values have been used in corn as the best estimator of "functional mortality" and predictor of potential effectiveness of Bt corn [ 52 ].

Field Efficacy of Bt Eggplant Lines Containing Event EE-1 Against the Primary Target Pest, ESFB

Efficacy is the capacity of the host plant to affect the survival of the insect pest. Host plant resistance can be measured as a percentage of damage to the foliage or fruiting parts, reduced crop stand, yield and vigor [ 53 ]. It can also be measured based on insect characteristics which include number of eggs laid, aggregation, food preference, growth rate, food utilization, mortality and longevity. In this study, the field efficacy of Bt eggplants against EFSB was evaluated based on the following parameters: (1) percentage of EFSB-damaged shoots; (2) percentage of EFSB-damaged fruits; (3) EFSB larval counts; and (4) survival and fecundity of field collected larvae.

The results of the three season trials indicated consistent, high field efficacy in all Bt eggplant lines tested relative to their non-Bt eggplant comparators i.e. non- Bt near-isoline counterparts and check variety. Even under the most severe pest pressure during trial 2, the Bt eggplant lines demonstrated high level of control of EFSB shoot damage (98.6–100%) and fruit damage (98.1–99.7%) and reduced EFSB larvae infestation (95.8–99.3%). Among the lines tested, Bt M4 showed the lowest % efficacy in shoot (95.3%) and fruit damage (94.1%) and M8 the lowest % efficacy for EFSB larval count (88.4%). However, these lower results were not consistently observed in every trial and their efficacy levels were always much better compared to any of the non-Bt comparators tested.

In addition to Cry1Ac expression and plant damage, we assessed the effect of Bt eggplants on EFSB survivorship and fecundity. This was done to assess the potential for evolution of resistance of EFSB to Bt eggplant. Resistance among insects occur when genetic variation in a population enables a subset of individuals to survive on doses lethal to the majority of the population when feeding on the Bt plant and subsequently produce viable offspring [ 54 , 55 ]. It is noteworthy that results showed few adults emerged and no eggs and viable offspring were produced in mating adults from larvae collected in Bt eggplant lines lending further evidence of very high field efficacy against EFSB. Furthermore, the diminished capacity for normal insect development and reproduction suggest the Bt eggplant lines tested in these trials express a high dose, a key component in the high dose-refuge management strategy [ 56 ].

Taken together, the results obtained from the two-year field testing in Pangasinan support the conclusion that Bt eggplant OP lines developed by the University of the Philippines Los Baños and containing event EE-1 possess a novel trait that provides outstanding control of EFSB making them superior to the conventional counterparts and the check, particularly when the pest pressure is high. Commercial production of Bt eggplant has great potential to reduce yield losses to EFSB while dramatically reducing the reliance of growers on synthetic insecticides to control this pest, reducing risks to the environment, to worker's health, and to the consumer [ 7 , 8 , 10 , 57 ].

Before Bt eggplant seeds are made available for commercial propagation, it is essential to develop an insect resistance management (IRM) plan to manage the risk of resistance evolution in the target pest. The use of high-dose/refuge strategy has been postulated to delay the potential evolution of insect resistance to the Bt crops by maintaining insect susceptibility [ 56 ]. This has been implemented for Bt cotton and Bt corn and the same needs to be extended to Bt eggplants. Some of the key elements in an IRM strategy include information on the expression profile of an insecticidal protein in the Bt crop, the inherent susceptibility of the insect, the number and dominance of genes involved, and the availability of susceptible plants as refuge. Results of the studies presented in this paper indicate that Bt eggplant OP lines expressed the Cry1Ac protein in relevant plant parts primarily attacked by EFSB at the appropriate growth stages throughout the productive life of the crop. More importantly, the amount of Cry1Ac detected in the Bt eggplant shoots and fruits remained sufficiently high to have significant activity against EFSB when compared to the baseline limits previously reported [ 21 , 28 , 50 , 51 ]. Furthermore, the Bt eggplant OP lines exhibited very high levels of field efficacy against EFSB and severely diminished the capacity of EFSB to reproduce successfully.

Prior to the commercial production of Bt eggplant in the Philippines, a structured refuge management strategy will be required. In addition to a structured refuge, the presence of many conventional non-Bt eggplant varieties and alternate wild Solanum hosts commonly present in uncultivated peripheral lands (i.e., unstructured refuges) will serve as a source of susceptible EFSB alleles in the population to slow the evolution of resistance in EFSB. Collectively, the results of this study suggest the possibility of a high-dose/refuge strategy for Bt eggplants. A stringent implementation of high-dose/refuge IRM plan within the context of integrated pest management (IPM) could help delay the potential development of resistance of EFSB to the Bt protein in UPLB Bt eggplant lines.

Materials and Methods

Confined field trials were conducted in the Philippines to evaluate product performance and assess potential environmental risks of UPLB Bt eggplants compared to their non-Bt comparators i.e. non-Bt near-isoline counterparts and the commercial check or reference variety. The field testing site located in the province of Pangasinan, the Philippines, best represented the agro-climatic conditions and production practices in the largest eggplant growing region (Region I or the Ilocos Region) in the country. Pangasinan has Type 1 climate characterized by two pronounced growing seasons: dry, from November to April; wet, during the rest of the year. Eggplant cultivation in Pangasinan is higher during the dry season (DS). Farmers in Pangasinan plant eggplant after rice starting in the months of September to October (planting season) and harvest during the months of December to April. Some farmers also plant during the off-season, which starts at the end of the dry season and harvest during the early wet-season. The province of Pangasinan alone has the widest production area (18.4%) and contributes the largest volume (31.9%) of eggplant produced in the country (2005–2014) [ 5 ]. The Pangasinan field trial site represented the conditions in small-holder farmer’s fields that experience very high natural incidence of EFSB pressure compared with other trial sites.

Three replicated confined field experiments were conducted in Bgy. Paitan, Sta. Maria, for three seasons from March 2010- October 2012. These trials were conducted under natural field infestation of EFSB and without application of lepidopteran-specific insecticide sprays. The studies were conducted in a comparative manner. Bt eggplant lines were evaluated in comparison with the conventional non-Bt comparators consisting of the corresponding non-Bt counterparts with similar genetic backgrounds (recurrent parents/near-isolines) and a National Seed Industry Council (NSIC)-approved commercial open-pollinated variety (OPV) as check or reference genotype. OPVs are standard varieties, which have stable characteristics and produce seeds that will grow into plants more or less identical to their parent plants.

Plant Materials, Experimental Design and Regulatory Conditions

The experimental materials used in the series of three confined field experiments are listed in Table 4 .

1 unsprayed = no lepidopteran-specific insecticide applied

2 BC n = number of backcrossing; F n = filial generation

3 From sowing to end of fallow period

4 D2, D3 = promising advanced Bt OP lines developed through conventional backcross breeding between improved line selection from Dumaguete Long Purple (DLP) and Mahyco eggplant event EE-1; M1, M4, M8 = promising advanced Bt OP lines developed through conventional backcross breeding between improved line selection from cultivar Mara and Mahyco eggplant event EE-1

5 DLP = open-pollinated improved line selection from Dumaguete Long Purple public variety; Mara, Mara S1, Mara S2 = open-pollinated improved line selections from the Mara cultivar developed by UPLB-IPB Vegetable Breeding Division

6 National Seed Industry Council (NSIC)-registered commercial open-pollinated eggplant variety

Plant materials

The Bt eggplant OP lines (D2, D3, M1, M4, M8) used as test entries in the field trials are advanced breeding lines (BC 3 F 4 to BC 3 F 6 ) derived from initial crosses of Mara selection x Mahyco elite line, ‘EE-1’ and DLP selection x Mahyco elite line, ‘EE-1’. The non-Bt comparators were: (1) DLP as the non-Bt counterpart genotype of Bt D2 and D3 OP lines; (2) Mara, Mara 1 or Mara S2 as the counterpart genotypes for M1, M4 and M8; and (3) Mamburao, a non-Bt eggplant OP variety approved by the NSIC [ 58 ] as the check or reference genotype.

Experimental Design and Field Layout

Each field experiment was planted in randomized complete block design (RCBD) with four replications, 4–6 rows/plot and 10 plants per row. The perimeters of each field experiment were surrounded by five rows (1 m between rows) of conventional non-Bt eggplant OP as pollen-trap plants. The experimental set up was conducted in a fenced facility with restricted access. A 200-meter radial distance isolated the field trial site from the nearest eggplants in the area.

Permissions

All field trials were conducted in accordance with the Department of Agriculture Administrative Order No. 8 Series of 2002 for field testing ( www.biotech.da.gov.ph ). The Bureau of Plant Industry (BPI) issued the corresponding Biosafety Permit for Field Testing in Bgy. Paitan, Sta. Maria, Pangasinan. The biosafety permit conditions were complied with throughout the conduct of every field experiment and associated greenhouse and laboratory activities. All sample collection and transport of materials were done under the supervision of the duly designated biosafety trial inspectors following the prescribed biosafety procedure for sample collection, handling and transport.

Crop Establishment, Management, Harvesting and Termination

Seedling establishment.

Seeds of UPLB Bt and non-Bt eggplant entries (treatments) were sown in pots with sterilized soil 30–34 days before transplanting. The germinated seeds were pricked (transferred individually in seedling trays), 7–8 days after sowing (DAS) and maintained inside the BL2 greenhouse at UP Los Baños. At 28–30 DAS, representative seedlings for the seed lot of each entry were tested for presence or absence of Cry1Ac using immunoassay or gene strip test kit, DesiGen Xpresstrip (DesiGen, Maharashtra, India), as described in Ripalda et al . [ 25 ]. Excess transgenic seedlings were disposed of properly in a disposal site inside the BL2 greenhouse. Seedlings of Bt and non-Bt eggplant test entries, check varieties and pollen traps were transported from UP Los Baños to the confined field testing site in Bgy. Paitan, Sta. Maria, Pangasinan for transplanting.

Cultural management

The confined field trials were managed based on the national cooperative trial guidelines for eggplant [ 59 ] and prevalent agronomic practices for eggplant growing in the region, including site preparation, tillage, and nutrient applications. Manual watering of plants was done during the first month after transplanting and shifted to overhead and/or furrow irrigation as plants grew and required greater amounts of water. At times of continuous heavy rain during the trial period, trenches or canals were dug to keep the soil near the roots from being waterlogged and to reduce the incidence of bacterial wilt infection. Staking of plants was done to provide additional support as the number and size of fruits increase and during periods of strong winds and rain. Branches were kept off the ground to prevent the fruit from becoming deformed.

Pest management

No lepidopteran-specific insecticide sprays were applied during the entire duration of the trials. Management of other arthropod pests and diseases was done by application of recommended IPM practices, primarily sanitation and withholding of pesticide use as long as possible to enable the proliferation of natural enemies. Whenever populations of leafhoppers and mites rose to very high level, they were controlled with the application of insecticides with reduced risk and without activity against EFSB (a.i. thiamethoxam) and sulphur, respectively.

Termination, disposal and fallow period

After the final harvest, each field experiment was terminated. All above- and below- ground plant parts were removed from the field and disposed of properly following the prescribed procedure indicated in the Biosafety permit. The field was plowed, irrigated and observed for volunteer plants 7, 14 and 30 and 60 days after termination. The field was kept fallow for at least 60 days after termination.

Data Collection and Analysis

Determination of cry1ac protein expression.

Cry1Ac protein expression study was conducted in trial 1 and trial 2, which represented the two eggplant growing seasons in Pangasinan, i.e. wet/off-season and regular dry season planting, respectively. Because trial 3 was also planted during the same season as trial 1 (wet/off-season) and for cost consideration, Cry1Ac protein analysis was not performed from samples obtained in this trial.

Sample collection used was based on the protocol previously described in Ripalda et al . [ 25 ]. Different plant parts from at least five plants from among the 16 plants in the two inner rows/replicate plot were collected. Terminal leaves were collected at the vegetative (up to 25 days after transplanting, DAT), reproductive (25–60 DAT) and late reproductive (60–80 DAT) stages of the crop. Flowers and immature fruits were collected during reproductive and late reproductive stages. Fruit samples were collected during the harvest period. Stem and roots were collected at termination (around 150 DAT). All samples collected were kept in an icebox and transported to the laboratory. Flesh and skin of immature fruits, but avoiding seeds, were separated in thin slices. Stems and roots were washed prior to storage. The woody portion of the stems was used for analysis. All samples were kept in a -80°C biofreezer until further processing and then freeze-dried at -60°C for 1–5 days until crisp. Dried samples from three plants per plot per plant part were bulked and placed in a 2.0 mL microfuge tube. Bulked samples were homogenized using two 6-mm steel beads and the ground samples were put in sealed containers and stored at 4°C until use.

Quantification of Cry1Ac was done through an enzyme-linked immunosorbent assay (ELISA). Commercially available quantitative ELISA kits (DesiGen Cry1Ac QuanT) specific for the Cry1Ac protein were procured from Mahyco (Maharashtra, India). Five milligrams of the powdered samples were weighed and analyzed. Chilled extraction buffer prepared as specified in the kit was added to the weighed samples. A dilute (up to 1:8) trypsinized protein extract was loaded to the pre-coated plates. Positive and negative controls and standards were prepared and loaded according to the instructions in the kit. Antibodies, wash buffer and substrate for detection (pNPP) used were also from the kit. Absorbance readings of the samples were made at 405 nm. According to the manufacturer’s instruction, the assay is considered valid when the mean absorbance reading of the blank is ≤0.246, mean absorbance reading of the standards with the highest concentration of Cry1Ac is ≥1.305, % residual of back calculated concentration of standards are 20 ng/ml– 125 ng/ml standards: ≤15%; 0.625 ng/ml standard ≤25% and R 2 of the standard curve is ≥0.98.

Data on Cry1Ac concentrations from different plant parts and different developmental stages of the Bt eggplant lines were analyzed by one-way analysis of variance using PROC MIXED in SAS v.9.1.3 [ 60 ]. Means were separated using Tukey’s HSD at α = 0.05. Data available from the Dryad Digital repository: http://dx.doi.org/10.5061/dryad.ks131 [ 61 ]

Evaluation of Field Damage by EFSB

Fruits were harvested from the 16 plants located in the inner two rows (12 m 2 ) of each plot. During each harvest period, the harvested fruits per plot were carefully cut open and examined for the presence of EFSB larvae or signs of EFSB damage and tunneling, sorted as with or without EFSB-damage, counted and weighed separately.

Data gathered:

• Percentage (%) damaged shoots per plot–calculated from the number of damaged shoots due to EFSB recorded from five shoots per plant from 16 inner row plants per plot at weekly intervals starting at two weeks after transplanting (WAT) for 10 observation periods.
• Percentage (%) damaged fruits per plot—calculated from the total number of EFSB-damaged fruits over the total number of fruits harvested from 16 inner row plants per plot. Harvesting was done every 3–4 days. Data were collected from 10–17 harvest periods prior to the termination of the experiment.
• EFSB larval counts (no. larvae/plot)–All harvested fruits from the 16 inner row plants per were cut open to check for the presence of EFSB larvae. The number of surviving EFSB larvae found inside the fruits per replicate plot were recorded every harvest period.
• % Efficacy (or Level of control)–calculated based on the formula (1- Bt/nonBt)*100% for % EFSB-damaged shoots, damaged fruits and EFSB larval counts
• Survivorship and fecundity–All surviving larvae collected per plot per harvest period were transferred to individual plastic cups and labeled. Each cup was provided with a slice of eggplant fruit from which the larva was collected. The cups were then brought to the UPLB-IPB Entomology P2 Laboratory and reared continuously in their respective hosts (Bt or non-Bt) until the adult stage. The number of individuals that successfully reached pupal and adult stages was recorded. Pairs of surviving adults from Bt and from conventional non-Bt lines were mated, placed in oviposition chambers and observed for egg deposition and hatching of offspring.

Data transformation was used to improve the normality of variables due to markedly skewed data or heterogeneous variances of Bt and conventional non-Bt entries. Data collected were transformed to sqrt (Y+0.5), arcsin (sqrt(Y/100)) or log 10 (Y+1) as appropriate. Transformed data on percentages damaged shoots and fruits, larval counts and feeding tunnel lengths were subjected to one-way analysis of variance and analyzed using PROC MIXED in SAS v.9.1.3 [ 60 ] and means were separated using Tukey’s HSD at α = 0.05. Pairwise mean comparisons by contrast between each Bt and its respective non-Bt counterpart and check variety were done for all parameters gathered using PROC MIXED. Data available from the Dryad Digital repository: http://dx.doi.org/10.5061/dryad.ks131 [ 61 ]

Supporting Information

Trials 1 to 2. CY 2010–11, Sta Maria, Pangasinan, Philippines.

Trials 1 to 3. CY 2010–12, Sta. Maria, Pangasinan, Philippines.

A: Trial 1; B: Trial 2; C: Trial 3. CY 2010–12, Sta. Maria, Pangasinan, Philippines.

Acknowledgments

We gratefully acknowledge the critical support and valuable contributions of these institutions. This research was co-funded by the United States Agency for International Development (USAID) through Cornell University Agricultural Biotechnology Support Project II (ABSPII), the Republic of the Philippines Department of Agriculture- Biotechnology Program Office (DA- Biotech BPO) and the Instiute of the Plant Breeding, College of Agriculture, University of the Philippine Los Baños (UPLB). We thank the Maharashtra Hybrid Seeds Co. Pvt. Ltd. (Mahyco) for providing access to eggplant event EE-1 and regulatory-related information, and for various technical assistance/advice in the conduct of laboratory and field activities; and Cornell University and Sathguru Management Consultants for facilitating the technology transfer. We also acknowledge the assistance of UPLB Foundation Inc., the executing agency for the ABSPII project in the Philippines.

We sincerely thank the following Bt eggplant staff for their various valuable contributions: OO Silvestre, MMM Abustan, RN Candano, RP Urriza, ER Maligalig, SA Baldo and MM Marin for field establishment and management and lab/field data collection; RR Ripalda, RB Frankie, ML de Vera and AD Austral for sampling and Cry1Ac analysis; and ZJ Bugnosen for assistance in regulatory-related and administrative activities. We thank B. Bartolome for statistical advice and JA Estrella and RN Candano for assistance in statistical analyses; and N. Storer for reviewing an earlier draft of the manuscript. Special thanks to the people of Sta. Maria, Pangasinan especially Ret. Gen. M Blando, Dr. R Segui for all forms of assistance during the conduct of the trials.

Funding Statement

This research was funded through the United States Agency for International Development (USAID Cooperative Agreement GDG-A-00-02-00017-00) to Cornell University Agricultural Biotechnology Support Project II (ABSPII), and matching funds from the Republic of the Philippines Department of Agriculture- Biotechnology Program Office (DA- Biotech BPO) and the University of the Philippine Los Banos (UPLB). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Data Availability