Insecticide resistance-associated mutations in chinese Spodoptera exigua populations: prevalence characteristics and...

The beet armyworm, Spodoptera exigua, a notorious agricultural pest, poses an increasing threat in China. This study aimed to elucidate the frequency of resistance-associated mutations across 11 S. exigua populations in China and assess the effectiveness of allele-specific PCR (AS-PCR) for rapid mutation detection. We employed sanger sequencing to identify reported mutations in key resistance genes including ace1, voltage-gated sodium channel (VGSC), ryanodine receptor (RyR), and CYP9A186, with subsequent validation of AS-PCR results against sequencing data. Our findings revealed that ace1 mutations G311S and F443Y were present at about 50% frequency across populations, exhibiting a mutually exclusive pattern-where homozygous G311S was linked to the wild-type F443Y, and vice versa. For VGSC, the L1014F mutation, associated with pyrethroid resistance, varied in prevalence from 50% to 100%, whereas the V1848I mutation, linked to indoxacarb resistance, reached up to 48.21%. The RyR I4790M mutation, conferring diamide resistance, was found at a fixed rate of 100% in ten populations, except for SXXP20 (52.08%). The CYP9A186 F116V mutation, relevant to avermectin resistance, ranged from 56.25% to 97.22%. The AS-PCR method demonstrated over 95% accuracy, perfectly matching sequencing results in most populations. This research not only highlights the widespread, multi-class insecticide resistance in China's S. exigua populations, but also provides a rapid and cost-effective tool for the monitoring of such resistance. These findings carry important implications for informing the sustainable management of S. exigua in agricultural systems.