Abstract: 【Aim】 This study aims to select suitable reference genes in the multi-pesticide (abamectin, fenpropathrin and spirodiclofen) resistant strain (Mp-R) of T. urticae by quantitative real-time PCR (RT-qPCR). 【Methods】 Eight candidate reference genes including 5.8S rRNA, α-tubulin, TBP,β-actin , ELFn, RPL13a, GAPDH and SDHA were chosen. The stability of these candidate reference genes was investigated by using three softwares (GeNorm, NormFinder and BestKeeper). Then the expression of CYP392A subfamily gene in P450 enzyme system of T. urticae was analyzed by using different reference genes. 【Results】 EFLn was confirmed the most suitable reference gene in the sensitive strain (SS) and the multi-pesticide resistant strain (Mp-R) of T. urticae by geNorm, NormFinder and BestKeeper softwares. The expression level of CYP392A1 was up-regulated significantly in the eggs of the Mp-R strain, and the expression levels of CYP392A16 gene in various developmental stages of the Mp-R strain was significantly higher than the same stage of the sensitive strain of T. urticae after 40-generation selection with the multi-pesticides. The expression levels of CYP392A16 gene in various developmental stages of the Mp-R strain was significantly higher than those in the same stage of the sensitive strain of T. urticae. The expression levels of other genes were not significantly different between the Mp-R strain and the sensitive strain. 【Conclusion】 EFLn gene is confirmed the most suitable reference gene in the multi-pesticide resistant strain and the susceptible strain of T. urticae. This work is contributable to the foundation for future gene expression studies in the resistant strain of T. urticae.

Key words: Tetranychus urticae, resistance, CYP392A, gene expression level, RT-qPCR