dsABCC1 and dsABCC3 Enhance the Insecticidal Activity of Chlorantraniliprole in Rice Stem Borer Chilo suppressalis

The rice stem borer (RSB), Chilo suppressalis, is one of the most destructive rice pests in China and chlorantraniliprole has been extensively used for its control over the past decade. However, the continuous and intensive application of chlorantraniliprole has accelerated the development of resistant RSB populations in field, thereby threatening sustainable rice production. In this study, a field resistant strain of RSB exhibited a 181.76-fold resistance level to chlorantraniliprole compared to a susceptible strain. To explore the potential involvement of ATP-binding cassette (ABC) transporters in chlorantraniliprole resistance, four candidate ABC transporter genes (CsABCC1, CsABCC3, CsABCA3 and CsABCD2) were analyzed in resistant and susceptible strains. Compared to the susceptible strain, the expressional levels of CsABCC1 and CsABCC3 were significantly upregulated by 1.58- and 1.38-fold, respectively, whereas of CsABCA3 and CsABCD2 showed non-significant differences in the resistant strain. RNA interference assays demonstrated that naked dsRNA induced only limited gene silencing, while chitosan-mediated dsRNA delivery significantly improved RNAi efficiency. Following feeding with chitosan-coated dsCsABCC1 and dsCsABCC3, the expression levels of both genes were reduced by 44.63% and 38.49%, respectively, relative to the control and the larval mortality increased following chlorantraniliprole treatment to 63.33% and 56.67%, respectively. In addition, silencing CsABCC1 caused a greater reduction in larval weight after insecticide treatment. These findings indicated that CsABCC1 and CsABCC3 are involved in chlorantraniliprole detoxification and may contribute to resistance. Overall, this study provides evidence for the functional involvement of ABC transporters in chlorantraniliprole resistance and highlights chitosan-mediated RNAi as a promising complementary approach for resistance management within integrated pest management programs.