Biochemical and Molecular Characterization of Native Isolates of Trichoderma Antagonistic against Sclerotium and Pythium Infecting Tobacco

Abstract

Twelve isolates of Trichoderma isolated from rhizosphere of tobacco antagonistic to Sclerotium and Pythium infecting tobacco were evaluated for production of HCN and extracellular enzymes, and their genetic diversity by RAPD and isoenzymes. All isolates showed HCN production ranging from 0.08 to 0.14 OD. The isolate TvJt1 produced maximum content of HCN but it was at a par with the isolate ThHt1 and ThJt1. The isolate ThJt1 showed the maximum and significantly higher chitinase activity followed by isolate TvHt2. The isolate TvHt2 showed maximum and significantly higher -1,3-glucanase activity when compared to all other isolates. Isolate TvHt2 showed nearly 61.66% higher -1,3-glucanase activity when compared to the isolate TvJt1. A total of 140 amplified fragments were produced by 15 primers in 12 isolates, of which 113 were polymorphic with 80.2 per cent polymorphism. The genetic similarity in RAPD was 33 to 90 % whereas it was 30 to 90% in isoenzyme markers. In RAPD, the pair-wise similarity between the isolates ThHt3 and ThJO1 was minimum (33%) whereas in isoenzyme system, the pair-wise similarity was minimum (30%) between the isolates ThJO1 and ThHt1. Clustering analysis by unweighted pair group method on arithmetic averages (UPGMA), in both the marker systems, isolates were grouped into two clusters mainly based on species specificity and region of isolation. The two marker systems showed nearly the similar results. There was no correlation between the RAPD/ isozyme pattern and the antagonistic potential of the Trichoderma isolates.