Bio-efficacy of Trichoderma isolates against Colletotrichum geolosporiodes in onion
*1G. Jameema and 2P. Balabaskar
Department of Plant Pathology, Faculty of Agriculture, Annamalai University, Annamalai Nagar-608002 (India) *1E mail id: jameema124@gmail.com
ABSTRACT
Twister blight of onion caused by Colletotrichum geolosporiodes is one of the most severe disease in onion-growing areas which results in yield loss up to 50-90% per cent, especially during the rabi season when climatic conditions are more favourable for the pathogen. Chemical management has been proven to be difficult, expensive, and detrimental to the environment for the management of C. geolosporiodes. Hence, biological management strategies is one of the best, since it is efficient against a wide range of soil-borne pathogens.Trichoderma spp., owing to their complex interactions with plant pathogens, which include parasitizing, secreting antibiotics, and fighting for space and resources were regarded as best antagonists against plant pathogens. In this line, ten different isolates of Trichoderma were isolated from rhizosphere soil in different onion growing areas of Tamil Nadu. They were screened against C. geolosporiodes under invitro conditions. Among the isolates, the isolate Tr-2 showed the highest inhibition percentage in Dual culture (82.00%) and poisoned food assay at (87.78%). Least inhibition of pathogen was recorded by the isolate Tr-3 (67.78%). Tr- 2 has recorded the highest inhibition percentage(100%) at 30% concentration of culture filtrate and Tr-4 recorded the least inhibition percentage with (77.62%) at 40% of concentration.