Diversity of culturable gut bacteria associated with brown planthopper, Nilaparvata lugens (Stål) and their role in imidacloprid degradation

The brown planthopper, Nilaparvata lugens (Stål), is a major pest of rice across Asia and has developed significant metabolic resistance to multiple insecticides. Microbiome-mediated insecticide resistance is of emerging interest in various insect pests, including N. lugens. In this study, we assessed the diversity of culturable gut bacteria in imidacloprid-susceptible (IMI-S) and imidacloprid-resistant (IMI-R) populations of N. lugens and their potential to degrade imidacloprid. Molecular characterization and phylogenetic analysis identified 13 bacterial isolates, representing ten families from three phyla: Proteobacteria, Actinobacteria and Firmicutes. The IMI-R population has contributed to nine of the 13 isolates. Screening for imidacloprid degradation identified four bacterial strains viz., Paenibacillus amylolyticus, Serratia marcescens, Acinetobacter soli and Brucella sp. associated with the IMI-R population were capable of growing in minimal salt medium supplemented with imidacloprid. Notably, S. marcescens and P. amylolyticus could utilize imidacloprid as a sole source of carbon and nitrogen, respectively. LC-MS/MS analysis revealed that P. amylolyticus and S. marcescens after 14 days of inoculation degraded 73.07 and 66.92% of imidacloprid (100 mg/L), respectively. These findings underscore a strong association between gut-microbial composition and insecticide resistance in N. lugens and highlight the potential of specific bacterial strains for microbiome-based pest and resistance management strategies.