COMPARATIVE ANTAGONISTIC PROPERTIES OF GLIOCLADIUM-VIRENS AND TRICHODERMA-HARZIANUM ON SCLEROTIUM-ROLFSII AND RHIZOCTONIA-SOLANI - ITS RELEVANCE TO UNDERSTANDING THE MECHANISMS OF BIOCONTROL

An isolate of Trichoderma harzianum which is less effective than G. vi rens in suppressing S. rolfsii and R. solani was compared with G. vire ns for various mechanisms of antagonism in vitro, viz., antagonism in dual culture/hyphal parasitism, parasitism of sclerotia, and antibiosi s. G. virens and T. harzianum were equally effective in parasitizing t he hyphae of R. solani. Only T. harzianum parasitized the hyphae of S. rolfsii, and the two antagonists were comparable with respect to anti biosis on the test pathogens. However, G. virens readily parasitized t he sclerotia of the test pathogens and was found to be more effective than T. harzianum in destroying the sclerotia. Under SEM, G. virens wa s found to colonize, penetrate, and sporulate inside the sclerotia of the test pathogens. Parasitism of sclerotia is suggested as the princi pal mechanism of biological control of S. rolfsii and R. solani by G. virens.