Caracterização dos efeitos letais e subletais da soja que expressa as proteínas inseticidas Cry1A.105, Cry2Ab2 e Cry1Ac para espécies de Spodoptera (Lepidoptera: Noctuidae)

Abstract

MON 87701 × MON 89788 × MON 87751 × MON 87708 soybean that expresses Cry1A.105, Cry2Ab2, and Cry1Ac insecticidal proteins and confers tolerance to glyphosate and dicamba is a potential tool for managing Spodoptera species in soybean in Brazil. In this study, we characterized the lethal and sub-lethal effects of Cry1A.105/Cry2Ab2/Cry1Ac soybean against Spodoptera cosmioides (Walker, 1898), Spodoptera eridania (Stoll 1782), Spodoptera albula (Walker, 1857) and genotypes of Spodoptera frugiperda (J. E. Smith 1797) (Lepidoptera: Noctuidae) resistant and susceptible to Cry1 and Cry2 proteins. These evaluations were also conducted with MON 87701 × MON 89788 soybean, which expresses Cry1Ac protein. Initially, bioassays were performed with Bt and non-Bt soybean leaves removed from plants at the phenological stages V4-5, V7-8, R2-3 and R3-4 to evaluate the neonate survivorship. Subsequently, the development of the species was also evaluated throughout the biological cycle in Bt and non-Bt soybeans. Finally, the fertility life table of Spodoptera species and was estimated to identify effects on population growth parameters. Results showed that Cry1A.105/Cry2Ab2/Cry1Ac soybean had high lethality (>92%) against neonates of S. cosmioides and S. albula. However, it showed low lethality in S. frugiperda genotypes homozygous for resistance to Cry1 and Cry2 proteins but reduced their population growth potential. Spodoptera frugiperda genotypes susceptible and heterozygous for Cry1 and Cry2 resistance were controlled by Cry1A.105/Cry2Ab2/Cry1Ac soybean, with no insects completing the biological cycle. This Bt soybean also caused intermediate mortality (60–83%) of neonates of S. eridania but no surviving larvae developed to adulthood, resulting in population suppression. No relevant lethal and sublethal effects of Cry1Ac soybean were detected in the Spodoptera species and genotypes evaluated. In summary, Cry1A.105/Cry2Ab2/Cry1Ac soybean caused high mortality of S. cosmioides, S. albula, and S. frugiperda genotypes susceptible to Cry1 and Cry2 and heterozygous for Cry1 and Cry2 resistance. This soybean also suppressed population growth of S. eridania but had minimal effects on S. frugiperda homozygous for resistance to Cry1 and Cry2 proteins. Cry1Ac soybean had minimal effects on all Spodoptera species and genotypes evaluated.