Effect of temperature on antagonistic and biocontrol potential of Trichoderma sp. on Sclerotium rolfsii.

Sclerotium rolfsii is a destructive soil-borne and post-harvest plant pathogen. Use of the antagonistic fungus Trichoderma sp. has been earlier reported by us to successfully control this pathogen under post-harvest conditions. In the present paper we report on the effects of temperature on the growth and biocontrol potential of Trichoderma sp. on S. rolfsii. Experimental results indicated that S. rolfsii and Trichoderma sp. have different temperature optima for growth: 30-35 degrees C for the pathogen and 25-30 degrees C for the antagonist. In dual culture, Trichoderma over-grew S. rolfsii at 25 degrees C and 30 degrees C, but at 35 degrees C and 37 degrees C, S. rolfsii over-grew the colony of Trichoderma. Trichoderma produced higher concentration of fungi-toxic metabolites in broth culture at higher temperatures. In bioassays using ginger slices and whole rhizomes, it has been demonstrated that Trichoderma is not very effective in suppressing S. rolfsii at temperatures above 30 degrees C. In light of these results, possible mechanisms of biocontrol of S. rolfsii as a post-harvest pathogen has been discussed. Storage temperature has been suggested as a critical factor in biocontrol of S. rolfsii.