Abstract

The small brown planthopper, Laodelphax striatellus, is an important agricultural pest primarily managed by chemical insecticides. However, the prolonged use of chemical insecticides fosters the development of pest resistance. In this study, a L . striatellus strain (TRS) with 24.32-fold resistance to thiamethoxam was established in the laboratory. The realized heritability ( h 2 ) of the TRS strain was estimated as 0.0228, and a ten-fold increase in resistance was achieved in only 4 generations under a selection pressure causing 90% mortality. Compared to the susceptible strain (SS), TRS displayed significantly higher cytochrome P450 activity (1.56-fold) and elevated transcription levels of 13 P450 genes. Among these, the expression of CYP303A1 showed the strongest induction (5.94-fold), and this upregulation was confirmed by additional gene expression profile analyses. Functionally, silencing CYP303A1 expression markedly increased TRS sensitivity to thiamethoxam. These results suggest that CYP303A1 is closely correlated with the development of thiamethoxam resistance in L. striatellus . Overall, the results of this study provide significant implications for optimizing thiamethoxam deployment strategies, thereby enhancing the targeted control of L. striatellus .