SELECTION OF NATIVE TRICHODERMA ISOLATES FOR THE MANAGEMENT OF SOIL-BORNE DISEASES IN TEA (CAMELLIA SINENSIS)D. JAGADISH BABU, A. JOHN PETER, A. BABU, S. MAIYAPPAN, K.C. KUMHAR AND V. BHADRA MURTHYAbstract Laboratory studies were carried out to evaluate the growth and bio-efficacy of three Trichoderma isolates from tea ecosystem of Dooars region in North Bengal viz., KBN-24, KBN-1/14 (ITCC Nr 7765) and KBN-29 (ITCC Nr 7764) in comparison with commercially available Trichoderma viride TV1-TNAU (ITCC Nr 6914), and Trichoderma harzianum TH-IIHR (ITCC Nr 6888). The in vitro antagonistic activity of all the five isolates against four economically important tea pathogens was carried out using dual culture technique. Isolates KBN-29 and KBN-1/14 recorded significant growth inhibition of Curvularia sp and Fusarium sp as compared to KBN-24, TV1-TNAU and TH-IIHR. The isolate KBN-29 also significantly inhibited the growth of Colletotrichum sp as compared to other tested isolates. However, TH-IIHR recorded significant growth inhibition in Pestalotiopsis theae followed by KBN-29 isolate. The strain KBN-29 was identified as best antagonist based on the z-score 3.139 followed by KBN-1/14 (0.4079), KBN-24 (-0.4550), TH-IIHR (-0.6925) and TV1-TNAU (-2.3994). When the isolates were allowed to grow in potato dextrose agar (PDA), the maximum growth was recorded in KBN24 (1.13 cm-d) followed by KBN29 (1.08 cm-d). Since KBN29 was shortlisted as the best bio-control agent for the management of select tea pathogens based on z-score, it was allowed to grow on potato dextrose medium, yeast molasses medium (YMM) and Sabourauds dextrose broth (SDB) to find out the best media for mass multiplication. Maximum sporulation (2.4X108 mL-1) and dry mass (5.56 g-L) yield was recorded in PDB. Yeast molasses medium (YMM) and Sabourauds dextrose broth (SDB) recorded 2.3X108 mL-1 and 2.2X108mL-1 of spore count along with 5.46 g-L and 5.36 g-L of dry mass, respectively.
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