Presence and impact of allelic variations of two alternative s-kdr mutations, M918T and M918L, in the voltage-gated sodium channel of the green peach aphid Myzus persicae

Background Pyrethroids have been widely employed in order to control several agricultural pests, including Myzus persicae. Target-site resistance is the main mechanism that confers insensitivity to this class of compounds and the most common amino acid substitutions are kdr (L1014F) and s-kdr (M918T), but recently another mutation in the s-kdr locus (M918L) has been described in French and Korean populations of M. persicae. Results Molecular analysis of several Italian populations of M. persicae by pyrosequencing revealed the presence of the new s-kdr mutation (M918L) in different forms. It was found in two different nucleotide polymorphisms (a/t or a/c substitution), in heterozygous or homozygous status, and also in combination with the classic kdr and s-kdr. Bioassays on populations carrying M918L mutation show that it strongly affects pyrethroid efficacy, particularly of type II pyrethroids such as lambda-cyhalothrin, whilst it has no effect against DDT. Conclusion This work contributes to add more information about the new s-kdr M918L mutation in M. persicae, describing a more complicated situation due to the possible combination with the classic L1014F and M918T. Our data open new questions on the origin of these new genotypes with different combinations of target-site mutations and also on their possible influence on control strategies