Molecular genetic analysis of resistance-associated mutations in the experimental lines of spider mite Tetranychus urticae Koch, selected for resistance to bifenthrin and abamectin

The spider mite Tetranychus urticae is a polyphagous pest that establishes high levels of resistance to acaricides in industrial glasshouses. In the present paper, spider mite lines selected for resistance to acaricides were used to compare point mutations in the key resistance-associated genes. Both resistant (R-) and susceptible (S-) lines were obtained after 188 and 44 generations of selection to bifenthrin and abamectin, respectively. In bifenthrin-selected mites, para sodium ion channel of the plasma membrane (para SC) locus was analysed and one non-synonymous and one synonymous point mutations were found. The same mutations were reported previously in T. urticae that developed resistance to bifenthrin under natural conditions. As for abamectin-selected lines, glutamate-gated chloride channel (GluCl) locus was analysed, and no mutations were found. Thus, the para SC mutations in strains and lines of mites with developed resistance to pyrethroid acaricides is a widespread phenomenon in T. urticae. Experimental selection results in mutations that are also formed under natural conditions and may therefore serve as a model to study acaricide resistance mechanisms in spider mites. On the other hand, mutations in GluCl gene of avermectin-resistant mites are not so common, inferring involvement of alternative mechanisms of resistance.