Sulfoxaflor resistance in Aphis gossypii: resistance mechanism, feeding behavior and life history changes

Sulfoxaflor, a novel sulfoximine insecticide, has been widely used to control sucking insect pests. In order to investigate the resistance mechanisms and potential adaptive costs (e.g., in feeding behavior and life history) associated with sulfoxaflor resistance, a sulfoxaflor-resistant (Sul-R) A. gossypii strain with 40.19-fold resistance was established by laboratory selection. This Sul-R strain developed different cross-resistance to neonicotinoid, pyrethroid and carbamate insecticides (resistance ratio values ranged from 5.62-fold to 35.90-fold). Three synergistic chemicals, piperonyl butoxide (PBO), diethyl maleate (DEM) and triphenyl phosphate (TPP), dramatically increased the toxicity of sulfoxaflor in the Sul-R strain with synergistic ratios of 7.37, 2.60 and 1.76, respectively. The activities of cytochrome P450 monooxygenase (P450), S, S, S-tributyl phosphorotrithioate (GST) and carboxylesterase (CarE) were also significantly higher in the Sul-R strain than the Sus strain. Meanwhile, twenty-five P450 genes were overexpressed in the Sul-R strain and suppression the expression of CYP6CY13-2 by RNAi significantly improved the susceptibility of Sul-R A. gossypii to sulfoxaflor. Furthermore, this Sul-R A. gossypii became more active in finding an appropriate position for feeding. They made more intercellular apoplastic stylet pathway events (C) than the susceptible strain. In addition, the Sul-R strain showed an increased relative fitness of 1.19. The fecundity of Sul-R adults was dramatically higher than that of the relatively susceptible aphids. Our results indicated that enhancing P450 activity and overexpression of P450 genes, especially the CYP6CY13-2 gene, likely contribute to sulfoxaflor resistance in A. gossypii and the resistance to sulfoxaflor can result in stimulated probing and fecundity.

Automated summary

The sulfoxaflor-resistant A. gossypii strain developed cross-resistance to neonicotinoid, pyrethroid, and carbamate insecticides. The resistance was associated with increased levels of cytochrome P450 monooxygenase, GST, and carboxylesterase activities, as well as overexpression of P450 genes, especially CYP6CY13-2. Additionally, the resistant strain showed enhanced probing behavior and higher fecundity compared to the susceptible aphids.