Antagonistic Potential and Molecular Characterization of Trichoderma Harzianum Isolates against Sclerotium Rolfsii Infecting Tobacco

Abstract

Ten isolates of Trichoderma harzianum isolated from rhizosphere of tobacco and other crops were evaluated for their genetic diversity and antagonistic potential against Sclerotium rolfsii, a fungal pathogen causing collar rot in tobacco. In dual culture, isolates WG 1, WG 3, GT 1 and DH were more aggressive in inhibiting the mycelial growth of the pathogen. The isolate WG 1 showed maximum production of HCN which reflected in the maximum inhibition of S. rolfsii growth by volatile compounds. Production potential of hydrogen cyanide, indole acetic acid and siderophore varied among the isolates. Siderophore production was not observed in the isolate KP. The level of polymorphism detected with different primers ranged from 70 to 100%. Out of 249 amplified fragments, 216 (86.74%) were polymorphic. The primers OPP 11, OPAB 1, OPL 4, PL 5 and OPL 6 were highly polymorphic (100%). Based on RA PD profiles, the pair-wise similarity coefficients among the isolates ranged from 0.46 to 0.85 with an average of 0.65. The minimum genetic similarity was observed between the isolates KP and BK (46%), whereas the highest (85%) was between the isolates GT 1 and GT 2. Cluster analysis by unweighted pair group method on arithmetic averages (UPGMA) grouped the isolates into two major clusters. The clustering pattern of the isolates was based on host and region with the exception of isolate KP. There was no correlation between the RA PD pattern and the antagonistic potential of T. harzianum isolates.