Induction of systemic resistance in grapevines against powdery mildew by Trichoderma asperelloides strains

Thirty four Trichoderma isolates were systematically screened for induction of systemic resistance in grapevines against powdery mildew disease. Trichoderma 5R, NAIMCC-F-01769, NAIMCC-F-01812 and NAIMCC-F-01951 were selected for field trials based on initial screening on potted plants. All the four isolates tested positive for production of plant growth promoting bio-chemicals, indole acetic acid, siderophore, ammonia, hydrogen cyanide and phosphate solubilization and produced chitinase, beta-1,3-glucanase, cellulase, amylase and protease. These four isolates were compatible with each other and were tested singly or as mixtures. In the three grapevine field trials conducted during the fruiting growth phase 2015-16 and 2016-17 and the vegetative growth phase 2016, the maximum reduction in powdery mildew severity was found in vines treated with 5R + NAIMCC-F-01812, followed by vines treated with 5R alone showing that the efficacy of 5R was slightly enhanced when used along with NAIMCC-F-01812. Total phenol contents, and chitinase and beta-1, 3-glucanase activities were highest in leaves of vines treated with 5R + F-01812 corroborating the field observations. The peroxidase and polyphenol oxidase activities were also high in leaves of vines under this treatment. Multilocus analysis using partial nucleotide sequences of act, rpb2 and tef1 genes showed phylogenetic affiliations of all four isolates to T. asperelloides.