Multiple detoxification genes confer imidacloprid resistance to Sitobion avenae Fabricius

Abstract

The English grain aphid, Sitobion avenae Fabricius, is one of the major wheat pests distributed worldwide. Insecticide application is typically effective for controlling S. avenae, However, S. avenae has developed resistance to multiple insecticides. Thus, it is crucial to elucidate resistance mechanisms in S. avenae. In this study, the mechanisms of resistance to imidacloprid in S. avenae and the risk of cross resistance to other insecticides were investigated. An imidacloprid resistant strain (SA-R) of S. avenae was established via continuous imidacloprid selection with 42.7-fold resistance compared with the susceptible population (SA-S). There was cross resistance in SA-R between imidacloprid and other insecticides tested (acetamiprid, abamectin, chlorpyrifos, and omethoate), with ratios ranging from 10.7- to 24.7-fold higher than SA-S. S, S, S-tributyl phosphorotrithioate (TPP), piperonyl butoxide (PBO), and diethyl maleate (DEM) had synergism with imidacloprid in the SA-R strain with 2.85-, 3.59-, and 2.14-fold reductions, respectively, in LC50 values. Additionally, the activities of cytochrome P450 (P450), glutathione-S-transferases (GST), and carboxylesterase (COE) were significantly higher by 2.69-, 1.42-, and 1.39-fold in the SA-R strain than in the SA-S strain. Based on the S. avenae transcriptome database, 11 P450, two COE, four GST, and two esterase (EST) genes that were significantly induced by imidacloprid were selected to compare gene expression levels between SA-R and SA-S. Fourteen detoxification genes of the 19 tested from the SA-R strain were overexpressed compared to those of the SA-S strain. Silencing of CYP6A14-1, CYP307A1, GST1-1-1, and COE2 by dsRNA feeding resulted in increased susceptibility of SA-R aphids to imidacloprid. These results provide evidence that detoxification genes including CYP6A14-1, CYP307A1, GST1-1-1, and COE2 contribute to resistance to imidacloprid in S. avenae, which was confirmed by RNA interference (RNAi) feeding.