Intraspecific diversity in the mechanisms underlying abamectin resistance in a cosmopolitan pest

Abstract

Pesticide resistance relies on a myriad of mechanisms, ranging from single mutations to a complex and polygenic architecture, and it involves mechanisms such as targetsite insensitivity, metabolic detoxification, or a combination of these, with either additive or synergistic effects. Several resistance mechanisms against abamectin, a macrocyclic lactone widely used in crop protection, have been reported in the cosmopolitan pest Tetranychus urticae. However, it has been shown that a single mechanism cannot account for the high levels of abamectin resistance found across different mite populations. Here, we used experimental evolution combined with bulked segregant analyses to map quantitative trait loci (QTL) associated with abamectin resistance in two genetically unrelated populations of T. urticae. In these two independent QTL mapping experiments, three and four QTLs were identified, of which three were shared between experiments. Shared QTLs contained genes encoding subunits of the glutamate-gated chloride channel (GluCl) and harboured previously reported mutations, including G314D in GluCl1 and G326E in GluCl3, but also novel resistance candidate loci, including DNA helicases and chemosensory receptors. Surprisingly, the fourth QTL, present only in only one of the experiments and thus unique for one resistant parental line, revealed a non-functional variant of GluCl2, suggesting gene knock-out as resistance mechanism. Our study uncovers the complex basis of abamectin resistance, and it highlights the intraspecific diversity of genetic mechanisms underlying resistance in a cosmopolitan pest.

Cross‐resistance, inheritance and biochemical mechanism of abamectin resistance in a field‐derived strain of the citrus red mite, Panonychus citri (Acari: Tetranychidae)

“…In the current study, abamectin resistance was polygenic in P. citri , which agreed with previous studies in other insects and mites, including T. urticae , T. cinnabarinus and P. xylostella 26,47,49 . Moreover, high‐resolution QTL mapping revealed a polygenic basis associated with abamectin resistance in T. urticae 50 . The development of pesticide resistance mediated by multiple genes was slower than that of monogenic resistance 51,52 .…”