Antifungal properties of native Trichoderma isolates against Sclerotium rolfsii and Pythium aphanidermatum infecting tobacco.

Isolates of Trichoderma native to tobacco rhizosphere, were evaluated for their antifungal properties against Sclerotium rolfsii and Pythium aphanidermatum, fungal pathogens causing collar rot and damping off diseases in tobacco. Isolate TvJt1 showed maximum HCN production (0.14 OD) followed by ThHt1 and minimum by isolates ThJnt and ThRt1 (0.08 and 0.09 OD). Indole acetic acid (IAA) production among the isolates varied from 6.48 to 14.82 pg ml(-1). Isolate ThJO1 produced maximum siderophore (13.48 m mol ml(-1), whereas isolate TvJt1 produced minimum content (6.24 m mol ml(-1)). Isolate ThJt1 showed maximum and significantly higher chitinase activity (62.12 p kat m;(-1)) as compared to other isolates, followed by isolate TvHt2. Isolate TvHt2 showed maximum and significantly higher ß-1, 3-glucanase activity (9.94 n kat ml(-1)) when compared to all other isolates. Isolate ThJt1 showed second highest activity of ß-1, 3-glucanase (6.75 n kat/ml). In dual culture, inhibition of mycelial growth of Pythium by isolate TvHt2 was maximum (72.45%) followed by ThJt1 whereas inhibition of mycelial growth of S. rolfsii by these two isolates was at a par (78.36% and 76.17%) and significantly higher than some isolates. Isolates TvHt2 and ThJt1 showed maximum and significantly higher inhibition of Pythium and Sclerotium growth (80.24% and 76%) by production of non-volatiles. Inhibition of Pythium and Sclerotium growth by production of volatile compounds by Trichoderma isolates ranged from 54.36 to 72.6% and 66.24 to 84.24% respectively. Hence, further investigation with potential isolates ThJt1 and TvHt2 in tobacco nursery may help to explore these bioagents for control of collar rot and damping off diseases in tobacco.