Abstract: 【Aim】 To determine the effects of insecticides at the sublethal dose on the expression of cytochrome P450 genes in the fall armyworm, Spodoptera frugiperda. 【Methods】 The toxicity of three insecticides (chlorantraniliprole, emamectin benzoate and Bacillus thuringiensis) against the 2nd instar larvae of S. frugiperda was assayed by leaf-dipping method, and the transcriptional levels of 16 P450 genes in the 2nd instar larvae of S. frugiperda treated with the sublethal dose (LC₁₀) of the three insecticides were measured by real-time quantitative PCR (RT-qPCR) at 48 h post treatment. 【Results】 The LC₁₀ values of chlorantraniliprole, emamectin benzoate and B. thuringiensis against the 2nd instar larvae of S. frugiperda were 0.931, 0.283, and 1 089.688 mg/L, respectively. In the 2nd instar larvae exposed to the LC₁₀ of chlorantraniliprole, 13 P450 genes including CYP4G75, CYP6AB12, CYP6B50, CYP321A7, CY321A8, CYP321A9, CYP321A10, CYP321B1, CYP337B5, CYP9A59, CYP9A58, CYP6AE44, and CYP6AE43 were up-regulated, and the transcription level of CYP6AE44 was 34.60-fold as high as that of the control. In the 2nd instar larvae exposed to the LC₁₀ of emamectin benzoate, 11 P450 genes including CYP4G75, CYP6AB12, CYP321A7, CY321A8, CYP321A9, CYP321A10, CYP321B1, CYP337B5, CYP9A58, CYP6AE44, and CYP6AE43 were up-regulated, and the expression level of CYP321B1 was 28.70-fold as high as that of the control. In the 2nd instar larvae exposed to the LC₁₀ of B. thuringiensis, 11 P450 genes including CYP4G75, CYP6AB12, CYP6AN4, CYP321A7, CY321A8, CYP321A9, CYP321A10, CYP321B1, CYP337B5, CYP6AE44, and CYP6AE43 were up-regulated, and the expression level of CYP6AE44 was 40.80-fold as high as that of the control. 【Conclusion】 Multiple P450 genes are up-regulated in the 2nd instar larvae of S. frugiperda in response to the sublethal dose of the three insecticides, and the expressions of CYP4G75, CYP6AB12, CYP321A7, CY321A8, CYP321A9, CYP321A10, CYP321B1, CYP321B5, CYP6AE44, and CYP6AE43 are induced by all the three insecticides.

Key words: Spodoptera frugiperda, cytochrome P450, insecticide; Bacillus thuringiensis, gene expression, sublethal dose