Antagonistic potential of Trichoderma isolates against castor wilt pathogen (Fusarium oxysporum F. sp. ricini Nanda and Prasad)

Evaluation of 21 isolates of five Trichoderma species (Trichoderma harzianum, T. viride, T. koningii, T. aureoviride and T. pseudokoningii) were evaluated against castor wilt causing pathogen Fusarium oxysporum f.sp. ricini Nanda and Prasad by dual culture method and through production of volatile inhibitors. Better isolate of each species were tested for its antagonism in pot culture experiment. Relationship of Trichoderma isolates with soil chemical properties was tested. All Trichoderma isolates had inhibitory effect on mycelial growth ofthe pathogen. Four T. harzianum isolates (Th1, Th2, Th3 and Th4) and two T viride isolate (Tv2 and Tv3) were most prominent showing antagonistic effects and fast growth to readily overgrow Foxysporum f.sp. ricini after 4 days of incubation. The results of volatile technique exhibited the highest radial growth inhibition of pathogen by isolate TV3 (67.07%) followed by TV2 (67.04%) and least effective was Tpk2 with 41.85 per cent inhibition. The better isolates among all five species were tested for their efficacy in pot culture experiment, which showed that T. harzianum isolate (Th 2) has maximum potential to reduce disease incidence.