In vitro antagonism of three Trichoderma spp. against Sclerotium rolfsii Sace., a collar-rot pathogen in elephant foot yam

The present investigation focuses on the screening of potential biocontrol agents against the collar-rot pathogen, Sclerotium rolfsii Sacc. on elephant foot yam, an intercrop of coconut in Andhra Pradesh. Among the three antagonists screened, Trichoderma viride Pers. Fr., T. harzianum Rifai and T. hamatum (Bon.) Bain, isolated and screened, T. hamatum inhibited the radial growth of S. rolfsii to an extent of 52.22 per cent followed by T. viride (44.11%) and T. harzianum (38.87%). All the three Trichoderma spp. were very effective in producing volatile and non-volatile metabolites that were suppressive to 5. rolfsii. Viability tests on sclerotia of S. rolfsii parasitized by Trichoderma spp. revealed complete colonization and replacement of sclerotial contents by 7^th day of parasitisation in case of T. hamatum and by 10^th day in case the of T. viride and T. harzianum.