Abstract
In the present study the production of α-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 α-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 α-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 α-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 α-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.
Highlights
Insect pests and fungal pathogens have become a source of concern as great losses to economically important crops are caused by them worldwide[1,2,3,4]
We evaluated the insecticidal potential of AGIs obtained from endophytic fungi against Spodoptera litura (Fab.)
Six cultures exhibited α-glucosidase inhibitory activity in the range of 55–93.4% with maximum being found in AKL-3 (93.4%) followed by AKL-9 (84.4%)
Summary
Insect pests and fungal pathogens have become a source of concern as great losses to economically important crops are caused by them worldwide[1,2,3,4]. Among bio-control agents, endophytes would be an ideal choice as these are integrated into the host plant They are the microorganisms which spend the whole or part of their life cycle colonizing inter- or intra-cellularly, in the healthy living tissues of the host, without causing any symptoms[7]. Plants artificially inoculated with endophytic fungi were found to demonstrate resistance against insect pests[15,16] These microorganisms synthesize a number of bioactive compounds mainly alkaloids, phenols, terpenoids, sterols etc.[17] which play a significant role in protecting their host plants from herbivores[18,19,20]. Α-Glycosidase enzymes are involved in processes during fungal growth and have a role in synthesis and extension of cell wall[30] Inhibitors of such enzymes could affect the growth and development of fungi leading to antifungal activity. C. gigantea was selected as it possesses, antifungal, antidiabetic and insecticidal potential[34,35,36] and their endophytes might produce metabolites with α-glycosidase inhibitory activity
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