A comprehensive assessment of insecticide resistance mutations in source and immigrant populations of the diamondback moth Plutella xylostella (L.)

BACKGROUND The diamondback moth (DBM) Plutella xylostella has developed resistance to almost all insecticides used to control it. Populations of DBM in temperate regions mainly migrate from annual breeding areas. However, the distribution pattern of insecticide resistance of DBM within the context of long-distance migration remains unclear. RESULTS In this study, we examined the frequency of 14 resistance mutations for 52 populations of DBM collected in 2010, 2011, 2017 and 2018 across China using a high-throughput KASP genotyping method. Mutations L1041F and T929I conferring pyrethroid resistance, and mutations G4946E and E1338D conferring chlorantraniliprole resistance were near fixation in most populations, whereas resistant alleles of F1020S, M918I, A309V and F1845Y were uncommon or absent in most populations. Resistance allele frequencies were relatively stable among different years, although the frequency of two mutations decreased. Principal component analysis based on resistant allele frequencies separated a southern population as an outlier, whereas the immigrants clustered with other populations, congruent with the migration pattern of northern immigrants coming from the Sichuan area of southwestern China. Most resistant mutations deviated from Hardy-Weinberg equilibrium due to a lower than expected frequency of heterozygotes. The deviation index of heterozygosity for resistant alleles was significantly higher than the index obtained from single nucleotide polymorphisms across the genome. These findings suggest heterogeneous selection pressures on resistant mutations. CONCLUSION Our results provide a picture of resistant mutation patterns in DBM shaped by insecticide usage and migration of this pest, and highlight the widespread distribution of resistance alleles in DBM. (c) 2022 Society of Chemical Industry.

Automated summary

This study investigated the frequency and distribution pattern of resistance mutations in the diamondback moth (DBM) across China. The results showed a widespread distribution of resistance alleles in DBM populations, with some mutations near fixation and others less common or absent in most populations. The frequency of resistance alleles remained relatively stable among different years, although there was a decrease in the frequency of certain mutations. Principal component analysis revealed clustering of immigrant populations with other populations, indicating a migration pattern from the Sichuan area of southwestern China. The study also found that most resistant mutations deviated from Hardy-Weinberg equilibrium, suggesting the influence of heterogeneous selection pressures on resistance mutations.