Temporal and spatial incidence of alleles conferring knockdown resistance to pyrethroids in the peach–potato aphid,Myzus persicae(Hemiptera: Aphididae), and their association with other insecticide resistance mechanisms

Abstract

AbstractThe peach–potato aphid,Myzus persicae(sulzer), is an important arable pest species throughout the world. Extensive use of insecticides has led to the selection of resistance to most chemical classes including organochlorines, organophosphates, carbamates and pyrethroids. Resistance to pyrethroids is often the result of mutations in thepara-type sodium channel protein (knockdown resistance orkdr). InM. persicae, knockdown resistance is associated with two amino-acid substitutions, L1014F (kdr) and M918T (super-kdr). In this study, the temporal and spatial distributions of these mutations, diagnosed using an allelic discriminating polymerase chain reaction assay, were investigated alongside other resistance mechanisms (modified acetylcholinesterase (MACE) and elevated carboxylesterases). Samples were collected from the UK, mainland Europe, Zimbabwe and south-eastern Australia. Thekdrmutation and elevated carboxylesterases were widely distributed and recorded from nearly every country. MACE andsuper-kdrwere widespread in Europe but absent from Australian samples. The detection of a strongly significant heterozygote excess for bothkdrandsuper-kdrthroughout implies strong selection against individuals homozygous for these resistance mutations. The pattern of distribution found in the UK seemed to indicate strong selection against thesuper-kdr(but not thekdr) mutation in any genotype, in the absence of insecticide pressure. There was a significant association (linkage disequilibrium) between different resistance mechanisms, which was probably promoted by a lack of recombination due to parthenogenesis.