In vitro efficacy of twenty five Trichoderma isolates (twenty were TCMS series viz., TCMS 2, 4, 5, 12, 14a, 14b, 15, 16, 24, 32, 34, 36, 43, 60, 62, 64, 65, 72, 85 and 93, and five Th series; Th 1, 3, 14, 19 and 32) were ascertained for their antagonistic activity against few major plant pathogenic oomycetes namely, Phytophthora infestans, P. parasitica and Pythium aphenidermatum using dual culture technique. P. infestans was isolated from infected potato leaves and Pythium aphenidermatum from infected brinjal. P. parasitica culture was collected from Central Potato Research Institute (CPRI), Simla. The present study was conducted at Biological Control Laboratory, Department of Plant Pathology, G.B. Pant University of Agriculture and Technology, Pantnagar. All the 25 Trichodrma isolates were found significantly effective against the test pathogens. TCMS-36 and TCMS-72 were found highly effective against P. aphinidermatum with 59.57 per cent inhibition of radial growth of the fungus. Maximum reduction in mycelial growth of P. infestans was recorded with isolate TCMS-64 (60.40%) followed by TCMS-65 (59.41%), TCMS-34 (58.42%), TCMS-24, TCMS-43 and TCMS-93 with 57.43 per cent inhibition. While, maximum inhibition of P. parasitica was recorded with TCMS-4 (92.75%) followed by TCMS-36 (92.23%), TCMS-2 (91.71%), TCMS-14a (91.17%) and TCMS-32 (90.67%). The selected potential isolates may be applied to sustainable and eco-friendly management of many major crop diseases caused by the oomycetes and other fungi.
