Performance da soja que expressa as proteínas inseticidas Cry1A.105, Cry2Ab2 e Cry1Ac para controle de lepidópteros-praga e manejo da resistência de insetos

Abstract

Genetically modified soybeans expressing Bacillus thuringiensis Berliner (Bt) proteins have revolutionized pest management throughout South America due to efficacy against major soybean pests. The pyramided genetically modified soybean [Glycine max L. (Merr.)] MON87751 × MON87708 × MON87701 × MON89788, expressing Cry1Ac, Cry1A.105 and Cry2Ab2 from Bacillus thuringiensis Berliner was approved for commercial use in Brazil. In this study were conducted laboratory, greenhouse and field studies to assess the performance of this Bt soybean technology against key soybean lepidopteran pests and support insect resistance management plans. Laboratory studies were carried out with purified proteins Cry1Ac, Cry1A.105 and Cry2Ab2 in artificial diet and soybean leaf discs to assess the susceptibility of the species, and greenhouse and field to assess the efficacy of the technology in high infestation and unde natural infestations in field conditions. Neonates of Anticarsia gemmatalis (Hübner), Chrysodeixis includens (Walker) and Helicoverpa armigera (Hübner) were susceptible to Cry1Ac (LC50 from 0.15 to 5.07), Cry1A.105 (LC50 from 0.79 to 48.22) and Cry2Ab2 (LC50 from 1.24 to 8.36) Bt proteins in diet-overlay bioassays. In laboratory leaf disc bioassays and greenhouse trials, MON87751 × MON87708 × MON87701 × MON89788 soybean as well as the individual components were effective in controlling A. gemmatalis, C. includens and H. armigera. Similarly, under field conditions, the pyramided event expressing Cry1A.105, Cry2Ab2 and Cry1Ac was highly effective at protecting soybean against C. includens. The individual proteins expressed by genetically modified soybean MON87751 × MON87708 × MON87701 × MON89788 killed all or nearly all the susceptible A. gemmatalis, C. includens and H. armigera, fulfilling an important pyramided Bt criterion which is the concept of redundant mortality, as a strategy for delaying resistance and sustaining the benefits of Bt soybean in Brazil.