Efficacy of bio control agents under in vitro against Alternaria porri (Ellis) Cifferi. Causing purple blotch in onion

Abstract

Purple blotch of onion caused by Alternaria porri (Ellis) Cif. is most devastating disease of onion in India has it causes huge loss under field conditions. In the recent days bio control agents are playing an important role in controlling the incidence of purple leaf blotch disease. Hence the study was undertaken to check the efficacy of nine fungal and eight bacterial antagonists under laboratory conditions by employing dual culture techniques. From the study it was clear that fungal bioagents takes upper hand in inhibiting the pathogen growth when compared to bacterial antagonists. Among nine fungal antagonists under study the highest mycelial inhibition was recorded in the isolate Trichoderma viride-1 with the per cent inhibition of 94.50 per cent. Followed by isolate Trichoderma harzianum-1 showing the inhibition per cent (90.19%). However the least inhibition of the mycelia growth 33.72 was noticed in Bacillus subtilis -3 isolate.