Biological Control of Damping Off of Okra caused by Rhizoctonia solani

Damping off of okra is known to occur worldwide and caused by different pathogens under variable climatic conditions.. In Himachal Pradesh Rhizoctonia solani was found major associated pathogen with damping off of okra in summer season grown crop. Twenty isolates of Trichoderma spp. isolated from different rhizosphere soil and five standard isolates of Trichoderma spp. already available were evaluated for their antagonistic activity in vitro against R. solani. Among all the isolates tested, Trichoderma sp. -2 was found best bioagents for inhibiting mycelial growth of R. solani (67.8%) in dual culture followed by Trichoderma sp.-9 (67.0%), Trichoderma sp. -6 (64.8%) and Trichoderma sp. -11(61.9%). Significantly, maximum mycelial growth inhibition (42.4%) of pathogen was with volatile compounds activity of Trichoderma sp.-2 while, filter sterilized culture filtrate of Trichoderma sp. -6 showed maximum pathogen mycelial inhibition. On the basis of morpho-cultural characteristics the potential bioagent isolates, Trichoderma sp.-6 and Trichoderma sp.-9 were identified as T. harzianum and T. viride, respectively. In mycoparasitic interaction, bioagents hyphae coiled around R. solani mycelium and after penetration lysed the pathogen hyphae. Under net house conditions, seed biopriming application method of bioagents was found superior for management of damping off of okra caused by R. solani than soil application, seed treatment and drenching.