BSA mapping reveals the architecture of pesticide resistance in Tetranychus urticae strain MR-VP

The MR-VP inbred strain of the two-spotted spider mite, Tetranychus urticae, was subjected to genomic sequencing with the Illumina method, as were 40 derived populations of a cross between MR-VP and another T. urticae strain, Wasatch. While the MR-VP inbred strain is highly resistant to the Mitochondrial Electron Transport Inhibitors of complex I (METI-I) acaricides fenpyroximate, pyridaben and tebufenpyrad, the Wasatch strain is susceptible. The derived populations were produced using an experimental design that combined bulked segregant analysis (BSA) genetic mapping as well as evolve and resequence methodology, and consisted of control (unselected), fenpyroximate-selected, pyridaben-selected and tebufenpyrad-selected populations with ten-fold replication. Using a permutation-based method to detect quantitative trait loci (QTL) from unselected and selected populations, shared as well as compound-specific QTL were identified. Candidate loci for resistance included the shared target of the three compounds (the T. urticae PSST homologue of complex I), cytochrome P450-reductase, and a non-canonical member of the nuclear hormone receptor 96 (NHR96) gene family.