Determination of organophosphate and carbamate resistance allele frequency in diamondback moth populations by quantitative sequencing and inhibition tests

Abstract

A quantitative sequencing (QS) protocol was established for predicting the frequencies of the A298S and G324A mutations in the diamondback moth ( Plutella xylostella) type-1 acetylcholinesterase (AChE) locus, putatively involved in organophosphate (OP) and carbamate (CB) insecticide resistance. The nucleotide resistant signal ratio at each mutation site was generated from sequencing chromatograms and plotted against the corresponding resistance allele frequency. Frequency prediction equations were generated from the plots by linear regression, and the signal ratios were highly correlated with resistance allele frequencies ( r 2 > 0.987). QS analysis of 15 representative regional field populations of DBM in Korea revealed that the allele frequencies of both A298S and G324A were over 70% in most field populations, implying the prevalent state of these resistance-associated mutations. In the AChE inhibition assay, all populations showed reduced sensitivity to paraoxon, DDVP, carbaryl, and carbofuran, supporting the notion that DBM resistance to OPs and CBs is widespread in Korea.