Interação de genes de resistência em plantas de soja visando ao controle de Rachiplusia nu (Guenée) (Lepidoptera: Noctuidae)

Abstract

Rachiplusia nu (Guenée) (Lepidoptera: Noctuidae) caterpillars have become a key pest of soybean crops in Brazil, showing low susceptibility to some Bt technologies. The combination of native resistance genes with Bt insecticidal proteins has emerged as a promising strategy for more effective and sustainable pest management. This study aimed to evaluate the effects of combining the Bt protein (Cry1Ac + Cry1F) with native resistance genes in soybean on the biological development of R. nu. Greenhouse experiments were conducted to assess oviposition preference under both choice and no-choice conditions, and laboratory bioassays were performed to evaluate insect biology. Four soybean genotypes were used: native resistance gene + Bt (NG+Bt), Bt only (Bt), native resistance gene only (NG), and a control genotype lacking both traits. In the choice test, the NG+Bt genotype exhibited antixenosis, receiving 56% fewer eggs than the control. This effect was not observed under no-choice conditions. In the biological assays, the NG+Bt treatment showed an antibiosis effect, reducing total survival (larva-to-adult) by 51.4%, extending the developmental cycle by four days, and resulting in the lowest net reproductive rate (R₀ = 185.5). In contrast, the Btonly treatment, although reducing survival by 74.3%, prolonged the larval period and resulted in the highest cumulative foliar consumption, suggesting a compensatory feeding response. The pyramiding of native resistance genes with Bt technology (NG+Bt) proved to be the most robust strategy, combining multiple modes of action— antixenosis and antibiosis—that reduce pest establishment and foliar damage, thereby outperforming the effectiveness of individual resistance mechanisms.