BackgroundParthenocarpy, or fruit development in the absence of fertilization, has been genetically engineered in eggplant and in other horticultural species by using the DefH9-iaaM gene. The iaaM gene codes for tryptophan monoxygenase and confers auxin synthesis, while the DefH9 controlling regions drive expression of the gene specifically in the ovules and placenta. A previous greenhouse trial for winter production of genetically engineered (GM) parthenocarpic eggplants demonstrated a significant increase (an average of 33% increase) in fruit production concomitant with a reduction in cultivation costs.ResultsGM parthenocarpic eggplants have been evaluated in three field trials. Two greenhouse spring trials have shown that these plants outyielded the corresponding untransformed genotypes, while a summer trial has shown that improved fruit productivity in GM eggplants can also be achieved in open field cultivation. Since the fruits were always seedless, the quality of GM eggplant fruits was improved as well. RT-PCR analysis demonstrated that the DefH9-iaaM gene is expressed during late stages of fruit development.ConclusionsThe DefH9-iaaM parthenocarpic gene is a biotechnological tool that enhances the agronomic value of all eggplant genotypes tested. The main advantages of DefH9-iaaM eggplants are: i) improved fruit productivity (at least 30–35%) under both greenhouse and open field cultivation; ii) production of good quality (marketable) fruits during different types of cultivation; iii) seedless fruit with improved quality. Such advantages have been achieved without the use of either male or female sterility genes.
Colorado potato beetle (CPB; Leptinotarsa decemlineata-Say) is a serious pest because it has developed resistance against insecticides. Three transgenic eggplant (Solanum melongena L.) lines bearing a mutagenized Bacillus thuringiensis Berl. gene coding for the Cry3B toxin, and the nontransformed control DR2-line were tested in field trials to assess their insect resistance. The transgenic lines 3-2, 6-1, and 9-8 were tested at two different locations in a randomized complete-block design. Samples were taken biweekly to assess the level of CPB and the presence of other insects. At harvest, total yield and fruit number per plot were recorded. Two transgenic lines showed high levels of resistance at both locations, as measured by CPB abundance and yield. Fruit production was almost twice as great in the highly resistant lines (3-2 and 9-8) as in the nontransformed control. The 6-1 transgenic line showed an intermediate level of resistance; it was similar to the control under heavy CPB pressure and was comparable to the other transgenic lines under milder infestations. Analysis by double antibody sandwich–enzyme linked immunosorbent assay (DAS–ELISA), performed on different tissues, revealed a lower amount of Cry3B protein in the 6-1 transgenic line than in lines 3-2 and 9-8. No detrimental effects on nontarget arthropods (including the chrysomelid Altica) were evident. Field observations confirmed that Bt may be able to control CPB infestation in eggplant, representing a potential effective and environmentally safe means of pest control.
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