Gut bacteria mediated insecticide resistance in cotton leafhopper Amrasca biguttula biguttula

Cotton leafhopper, Amrasca biguttula biguttula (Ishida) (Hemiptera: Cicadellidae) is a major sucking insect pest of cotton in India. Indiscriminate use of pesticides has led to the development of resistance to most of the recommended pesticide groups. Though there are multiple mechanisms and principles of insecticide resistance development in insects, the gut bacterial-mediated degradation of insecticides is relatively less explored. In the present study, the gut bacteria of field-collected, insecticide-resistant population of A. biguttula biguttula were compared with a laboratory-reared susceptible population. Among the five culturable gut bacteria from the imidacloprid-resistant population, only Enterococcus silesiacus CLHG1a exhibited growth in the agar medium amended with 50 and 100 ppm of imid­acloprid. The imidacloprid degrading capacity of E. silesiacus CLHG1a was further confirmed by HPLC analysis. E. silesiacus and Bacillus amyloliquefaciens CLHG2 showed higher esterolytic activity (0.348 and 0.309 mmoles/min/mg respectively). The esterase zymo­gram on native PAGE revealed a single major band. This study provides clear evidence that the bacterium E. silesiacus isolated from the gut of A. biguttula biguttula has the ability to degrade imidacloprid and may have played a role in the detoxification of pesticides.