The Evolution and\nMechanisms of Multiple-Insecticide\nResistance in Rice Stem Borer, Chilo suppressalis Walker (Lepidoptera: Crambidae)

The emergence of insecticide resistance in the rice stem\nborer, Chilo suppressalis, is a growing\nthreat to the sustainable\ncontrol of this important insect crop pest. Thus, monitoring of C. suppressalis populations for insecticide resistance\nand characterization of the underlying genetic mechanisms is essential\nto inform rational control decisions and the development of resistance\nmanagement strategies. Here, we monitored 126 C. suppressalis field populations from China for resistance evolution to four major\ninsecticides: 53 for chlorantraniliprole, 50 for abamectin, 74 for\ntriazophos, and 76 for spinetoram. Moderate to high levels of resistance\nwere observed to all four insecticides. Investigation of the underlying\nresistance mechanisms revealed multiple mutations in the ryanodine\nreceptor (RyR) and acetylcholinesterase 1 (AChE1), leading to target-site\nresistance to chlorantraniliprole and triazophos, respectively. In\ncontrast, the absence of mutations in the glutamate-gated chloride\nchannel (GluCl) and α6 nicotinic acetylcholine receptor (nAChR\nα6) subunit suggested that nontarget site mechanisms contribute\nto the multiple-insecticide resistance phenotypes observed in C. suppressalis. In this regard, we revealed overexpression\nof the uridine 5′-diphospho-glycosyltransferase <i>UGT33AF1</i> and cytochrome P450 <i>CYP6AB45</i> in C. suppressalis field populations. Functional characterization\nusing transgenic Drosophila demonstrated\nthat UGT33AF1 confers resistance against multiple insecticides <i>in vivo</i>, whereas CYP6AB45 does not appear to contribute\nto resistance. Collectively, our findings reveal the current status\nof resistance of C. suppressalis to\ninsecticides in China and uncover a diverse profile of resistance\nmechanisms in this species. These findings provide a foundation for\nthe development of sustainable strategies to effectively manage and\ncontrol this pest.