Effect of α-glycosidase inhibitors from endophytic fungus Alternaria destruens on survival and development of insect pest Spodoptera litura Fab. and fungal phytopathogens

In the present study the production of alpha-glycosidase inhibitors was used as a strategy to screen endophytic fungi with insecticidal and antifungal potential. Endophytic fungi were isolated from Calotropis gigantea L. (Gentianales: Apocynaceae) and evaluated for their alpha-glycosidase inhibitory activity. Maximum inhibitory activity was observed in an isolate AKL-3, identified to be Alternaria destruens E.G.Simmons on the basis of morphological and molecular analysis. Production of inhibitory metabolites was carried out on malt extract and partially purified using column chromatography. Insecticidal potential was examined on Spodoptera litura Fab. (Lepidoptera: Noctudiae). Partially purified alpha-glycosidase inhibitors induced high mortality, delayed the development period as well as affected the adult emergence and induced adult deformities. Nutritional analysis revealed the toxic and antifeedant effect of AKL-3 inhibitors on various food utilization parameters of S. litura. They also inhibited the in vivo digestive enzymes activity in S. litura. Partially purified alpha-glycosidase inhibitors were also studied for their antifungal potential. Inhibitors demonstrated antifungal activity against the tested phytopathogens inducing severe morphological changes in mycelium and spores. This is the first report on production of alpha-glycosidase inhibitors from A. destruens with insecticidal and antifungal activity. The study also highlights the importance of endophytes in providing protection against insect pests and pathogens to the host.