Mechanisms of first- to fourth-generation neonicotinoid resistance in Myzus persicae from Beijing peach orchards: Roles of target-site mutations and detoxification metabolism.

Myzus persicae is a globally destructive pest that has evolved severe resistance to neonicotinoids. However, the resistance status and underlying mechanisms in peach orchards of Beijing, China remain largely unknown. In this study, the resistance of six field populations collected from Beijing peach orchards against five neonicotinoids (representing first- to fourth-generation compounds) was investigated, and the molecular mechanisms were elucidated. Bioassays revealed resistance to imidacloprid (15.99-30.97-fold), acetamiprid (9.16-50.79-fold), sulfoxaflor (1.28-25.26-fold), thiamethoxam (6.12-16.95-fold), and dinotefuran (6.63-12.27-fold) across these populations. Mutation screening identified the known R81T and V101I mutations, along with a novel R81S substitution in the nAChR β1 subunit. Genotyping indicated that V101I single mutations were predominant (69.75% of individuals), while R81T/S + V101I combination mutations were detected in 22.56% of individuals. The results revealed that the R81T/S + V101I combination mutations confer substantially higher resistance (73.10->1146.79-fold) than V101I alone (13.73-394.21-fold) using monoclonal strains. Enzyme activity assays demonstrated that elevated P450 (1.18-1.56-fold), GST (1.32-2.18-fold), and CarE (1.64-2.59-fold) activities are associated with neonicotinoid resistance across all genotype backgrounds, with PBO showing the strongest synergistic effects (synergism ratios: 1.39-7.90). TPP and DEM exhibited synergism ratios ranging from 0.69 to 3.10. Molecular dynamics simulations showed that all mutations altered nAChR binding-pocket geometry, with combination mutations causing more pronounced structural perturbations and reduced imidacloprid binding affinity than V101I alone. These findings show that target-site mutations and detoxification enzymes act concertedly to drive neonicotinoid resistance in M. persicae, highlighting the need for insecticide rotation for sustainable management.