Isolation, identification and detoxification of intestinal endophytes of Helicoverpa armigera under different feeding

Abstract:

[Objective] This study compared the differentiation of endophytes in the intestines of Helicoverpa armigera under feeding normal diet and cottonseed meal diet, and studied gossypol tolerance and degradation effects of the screened strains, which provided theoretical and experimental support for further research on the detoxification of Helicoverpa armigera intestinal microorganisms in cotton-derived feed.[Methods] The gossypol tolerant endophytic bacteria were isolated in the intestinal tract of Helicoverpa armigera under different feeding conditions, selective culture of gossypol acetate single carbon source microorganism, and 16S rRNA gene sequence were analyzed and identified. The detoxification effect of the strains was analyzed by cultivated in a certain concentration of gossypol acetate liquid, and the compound ratio was used to study the effect of the compound bacteria on gossypol degradation.[Results] A total of 32 strains were isolated from Helicoverpa armigera, of which 17 strains were potential new taxon, and 14 were potential new species, and 3 were possible potential new genera. 17 strains were isolated from the intestinal tract of Helicoverpa armigera under feeding normal diet, belonging to 10 genera in 3 phyla of bacteria, 15 strains were isolated from the intestinal tract of Helicoverpa armigera under feeding cottonseed meal diet, belonging to 8 genera in 2 phyla of bacteria. With the increase of the concentration of gossypol acetate in the selective medium, the number of intestinal bacteria resistant to 100, 300, 500, 1 000 mg/kg gossypol acetate in the cottonseed meal feed groups were higher than those in the normal feed groups. Among all the tolerant strains, 15 strains had a degradation rate of more than 50%, and the highest degradation rate of gossypol was 90.83%. In the experiment of compound degradation of gossypol by intestinal bacteria, the degradation rate of gossypol in the experimental group were significantly higher than that in the control group (P<0.05), and the highest degradation rate of gossypol was 87.04%.[Conclusion] It was proved that there were some higher ability of degrading gossypol strains in the intestinal endophytic bacteria of Helicoverpa armigera, which enriches the resource of the strains degrading gossypol, and preliminary research on the potential of compound bacteria in the development and application of cotton-derived feed was conducted, which provided a new way for the biodegradation of gossypol in cotton-derived feed.

Key words:gossypol;Helicoverpa armigera;intestinal endophytic bacteria;isolation and identification;detoxification