Response of Soybean Exhibiting Expression of Bacillus Thuringiensis Cry1ac Gene Artificially Infected With Different Lepidopteran Pests.

Lepidopterans have a significant economic impact in soybean production system. This pest is especially important in areas with long growing seasons such as the southeastern USA, Brazil and North of Argentina. Recent advances in crop biotechnology offer transgenic plants as an efficient and environmentally alternative strategy for controlling lepidopteron insects. Transgenic expression of Bt (Bacillus thuringiensis subsp. Kurstaki) proteins have proven to be a highly effective method for controlling insect pests in nearly all major crop species. Crystal proteins Bt δ-endotoxins are specific to certain insect orders, protecting beneficial insect population. The objective of this study was to investigate the response of genetically modified soybean expressing cry1Ac gene to lepidopteran pests using artificial infestation. The pests evaluated were: Soybean looper (Rachiplusia nu and Pseudoplusia includens), Cotton bollworm (Helicoverpa gelotopoeon), Corn earworm (Helicoverpa zea) and Yellow bearcaterpillar (Spilosoma virginica). Soybean Plants without cry1Ac gene were used as a control. The infestation was done with 10 larvae per soybean plant. Two different larvae stages, L1 and L3, in vegetative plant stage (V3) were used. The experimental unit was the soybean plant and each experimental group included 10 soybean plants. Evaluations of defoliation damage were done 14-days after infestation. As a conclusion, soybean plants expressing cry1Ac gene had an excellent response against the evaluated pests with defoliation levels no greater than 5% in all cases. Soybean control plants showed defoliation levels as high as 80%.