Effects Of Double-stranded RNA Mediated CYP314A1 Gene Silencing On The Toxicity Of Methoxyfenozide And Lufenuron Complex On Spodoptera Exigua

Spodoptera exigua is an important pest of cotton,which is a great threat to cotton production.The control of S.exigua mainly depends on chemical pesticides.Methoxyfenozide and Lufenuron are two insecticides with different mechanisms to control the S.exigua.In this paper,we studied the synergistic effects of the compound combination of methoxyfenozide and Lufenuron on S.exigua,and searched for the ecdysone hormone pathway genes through transcriptome sequencing.RNA interference technology was used to detect the expression level of pathway genes,so as to clarify the mechanism of synergistic effects of the compound combination of two pesticides.At the same time,the toxicity changes of two insecticides were determined after the S.exigua was fed on the two weeds.The purpose of this study is to provide scientific basis for the establishment of green control technology system of S.exigua.The main research results are as follows:1.The changes in the gene expression levels of ecdysone hormone signaling pathway after different sublethal doses of methoxyfenozide were determined.After different sublethal doses of methoxyfenozide(LC₁₀=7.00ng/cm²,LC₃₀=21.00ng/cm²,LC₅₀=38.20ng/cm²),ecdysone hormone receptor（Ec R）expression was increased by 10.85,14.02 and 14.81 times,respectively.Compared with the control group,the expression level of Ec R decreased by 0.67,0.23 and 0.57 times after 24,48 and 72 h of ds Ec R injection,respectively.After 72 h of injection,the mortality rate of S.exigua treated with methoxyfenozide LC₃₀increased to 51.45%.2.The changes of gene expression levels in chitin biosynthesis pathway of S.exigua were determined after different sublethal doses of Lufenuron.After treatment with different sublethal doses(LC₁₀=13.37ng/cm²,LC₃₀=27.13 ng/cm²,LC₅₀=44.66 ng/cm²),the expression level of UAP was decreased to 0.79,0.62 and 0.43 times,respectively.The expression level of chitin synthase（CHSA）was down-regulated to0.79,0.62 and 0.43 times,respectively.Compared with the control group,the expression of UAP decreased by 0.67,0.31 and 0.11 times after 24,48 and 72 h of ds UAP,respectively.After 72 h injection,the mortality rate of S.exigua treated with Lufenuron LC₃₀ was increased to 47.91%.After 24 h,48 h and72 h of ds CHSA injection,the expression of CHSA decreased to 0.66,0.05 and 0.52 times,respectively.After 72 h ds CHSA injection,the mortality rate of S.exigua treated with LC₃₀ increased to 52.27%.3.The changes of ecdysone hormone synthesis and signaling pathway gene expression in different sublethal doses of the mixed were determined.After mixed with different sublethal doses(LC₁₀=8.80ng/cm²,LC₃₀=16.50 ng/cm²,LC₅₀=25.20 ng/cm²),the expression of CYP314A1 was up-regulated to 17.28,24.48 and 45.69 times,respectively.Compared with control group,the expression of CYP314A1decreased to 0.88,0.18 and 0.52 times after injection of ds CYP314A1 and feeding on Metoxyfenozide for24,48 and 72 h,respectively,and the mortality rate of S.exigua treated with LC₃₀ was increased to42.94%.The expression level of CYP314A1 was decreased to 0.82,0.26 and 0.38 times after injection of ds CYP314A1 and feeding on the compound mixture for 24,48 and 72 h,respectively.The mortality rate of S.exigua treated with the compound mixture LC₃₀ increased to 56.94%.The expression of CYP314A1decreased to 0.22,0.24 and 0.14 times after injection of ds CYP314A1 and feeding on the compound mixture for 24 h,48 h and 72 h,and the mortality rate of S.exigua treated with the compound mixture LC₃₀ increased to 60.42%.4.Toxicity tests of two kinds of weeds to methoxyfenozide,and mixed compound showed that:compared with the control,the toxicity of S.exigua larvae was decreased by eating quinoa,while the toxicity of S.exigua larvae was increased by eating solanum.