Investigation of lambda-cyhalothrin resistance in Spodoptera frugiperda: Heritability, cross-resistance, and mechanisms.

Lambda-cyhalothrin, a representative pyrethroid insecticide widely used for Spodoptera frugiperda control in China, poses challenges due to the development of resistance. This study investigates the realized heritability, inheritance pattern, cross-resistance, and resistance mechanisms to lambda-cyhalothrin. After 21 generations of selection, the lambda-cyhalothrin-resistant strain (G21) developed a 171.11-fold resistance compared to a relatively susceptible strain (RS-G9), with a realized heritability (h) of 0.11. Cross-resistance assays revealed that lambda-cyhalothrin-resistant strains showed no significant cross-resistance to the majority of tested insecticides. Genetic analysis indicated that lambda-cyhalothrin resistance in S. frugiperda was autosomal, incompletely dominant, and polygenic inheritance. The P450 enzyme inhibitor PBO significantly enhanced lambda-cyhalothrin toxicity in the resistant strains. Compared with the RS-G9 strain, the P450 enzyme activity was significantly increased and multiple P450 genes were significantly up-regulated in the lambda-cyhalothrin-resistant strains. RNAi targeting the most overexpressed P450 genes (CYP337B5 and CYP321B1) significantly increased the susceptibility of resistant S. frugiperda larvae to lambda-cyhalothrin. This study provides comprehensive insights into lambda-cyhalothrin resistance in S. frugiperda, and the results are helpful for developing effective resistance management strategies of this pest.