Comparative assessment of the gut bacterial diversity associated with field population of three rice stem borers and their in vitro insecticide degradation ability

Abstract

Insects harbour diverse range of microbes in the digestive tract. An investigation was carried out to isolate and characterize the culturable gut bacterial fauna of three stem borers attacking rice (Scirpophaga incertulus, Sesamia inferens and Chilo suppressalis) morphologically, biochemically and genetically (based on 16S rDNA sequences). Their ability to degrade two commonly used insecticides, i.e., chlorpyrifos and chlorantraniliprole was quantified in vitro through minimal media study using GC–MS and HPLC, respectively. There was a great variation in the gut bacterial composition of these three borers in spite of belonging to same guild and being collected from the same host (Varshadhan: CRLC-899) at the same time from ICAR-NRRI farm, Cuttack, India. Bacillus was prominent in S. incertulus and C. suppressalis whereas Stenotrophomonas was dominant in S. inferens. It is the first report of encountering B. pumilus, B. cereus and Acinetobacter calcoaceticus from the gut of S. incertulus and Paraclostridium from the gut of S. inferens. Chlorpyrifos and chlorantraniliprole was degraded to the tune of 44.87–92.02 % and 10.52 to 74.38 %, respectively. B. subtilis most efficiently degraded chlorpyrifos, while Klebsiella sp. and A. calcoaceticus were superior in degrading Chlorantraniliprole. The gut bacterial consortium of S. inferens was the most efficient in degrading the insecticides. The differential abilities of the gut bacterial isolates to degrade the insecticides provide insights for their possible involvement in xenobiotic detoxification in their host and further study on this aspect may improve management strategies of these pests. These insects can also serve as novel sources for profiling insecticide-degrading microbes for bioremediation programmes.