Antagonistic potential of Trichoderma hamatum against Alternaria porri causing purple blotch disease of onion through Gas chromatography-mass spectrometry (GCMS) analysis

Abstract

Alternaria porri causing purple blotch disease of onion is a destructive phytopathogen which causes severe loss in productivity. The present study aimed to unravel the antagonistic potential and efficacy of volatile organic compounds produced by various Trichoderma spp. against A. porri causing purple blotch disease of onion through Gas chromatography-mass spectrometry (GCMS) analysis. Ten isolates of Trichoderma species were isolated from the rhizospheric soil of healthy onion plants. Upon paired plate technique, the in vitro efficacy of ten Trichoderma isolates were tested against virulent isolate of Alternaria porri isolated from purple blotch disease infected onion plants. The Trichoderma isolate TIM2 showed 76.29 per cent inhibition on mycelial growth of pathogen. The effective Trichoderma isolate was identified as Trichoderma hamatum through the analysis of the rDNA of internal transcribed spacers (ITS) region and it was subjected to GC-MS analysis. The result of GCMS analysis indicated the highest peak area and retention time with major antimicrobial bioactive compounds like Tetradecane, 2,6,10-trimethy (20.327), (1.22) and Dodecane, 2-cyclohexyl (20.079), (2.14), Heptadecane (21.222), (9.50), Octadecane (22.379), (3.58), Eicosane, 9-cyclohexyl (22.578), (1.84), 2-Propenoic acid, pentadecyl ester (23.400), (10.37), 2,6,10,14-tetramethyl (23.567), (10.37), Eicosane (27.311), (2.34), Hexadecanoic acid, methyl ester (27.918), (4.43), n-Hexadecanoic acid (29.156), (3.59) and Tetrapentacontane, 1,54-dibromo (31.906), (3.33). These bioactive compounds identified through GCMS analysis from the crude extracts of Trichoderma hamatum exhibited a stronger antifungal activity against A. porri. Hence the application of T. hamatum for the management of purple blotch disease highly supress growth of the pathogen and reduce the disease incidence.