Production of lytic enzymes by Trichoderma strains during in vitro antagonism with Sclerotium rolfsii, the causal agent of stem rot of groundnut

摘要

Six Trichoderma strains (collected from IARI, New Delhi and MTCC, Chandigarh) were tested for their ability to inhibit soil-borne pathogen of groundnut mainly Sclerotium rolfsii (causing stem rot on groundnut). In vitro percent growth inhibition of S. rolfsii by various Trichoderma strains were recorded at 5th day after inoculation (DAI). Results obtained from the antagonism study indicated that Trichoderma viride (NBAII Tv 23) inhibited 61% growth of phytopathogenic fungi S. rolfsii followed by Trichoderma harzianum (NBAII Th1) (55% growth inhibition of pathogen). The specific activities of cell wall degrading enzymes chitinase, β-1,3 glucanase, protease and cellulase were tested during different incubation period (48, 72 and 96 h) when Trichoderma spp. grew in the presence of pathogen cell wall in synthetic media. The antagonist T. viride (NBAII Tv 23) induced higher chitinase and protease activity. The growth inhibition of pathogen during antagonism were positively correlated with coiling pattern of antagonists at 14th day after inoculation (DAI) as well as with the induction of chitinase, β-1,3 glucanase and total phenol content. However, the amount of cellulase and polygalacturonase recorded was least in these antagonists treatment. A significant positive correlation (p = 0.01) between percentage growth inhibition of test fungus and lytic enzymes (chitinase, β-1,3-glucanase and protease) in the culture medium of antagonist treatment established a relationship to inhibit growth of fungal pathogen by increasing the levels of these enzymes. Among all the tested Trichoderma strains, T. viride (NBAII Tv 23) was found to be the best strain to be used in biological control of plant pathogen S. rolfsii.