The antagonistic effect shown by fungi of the genus Trichoderma was assessed against the plant pathogens Sclerotium rolfsii and Verticillium dahlia, isolated from ornamental aster and strawberry, respectively. Twenty isolates of the antagonist were employed; they belonged to the species T. asperellum, T. hamatum, T. harzianum, T. koningiopsis, T. spirale and Trichoderma sp. Antagonism was investigated by means of dual culture tests and bioactive metabolite production based on the overlapping plate method. Most selected isolates had an inhibitory effect on the mycelial growth of S. rolfsii and V. dahlia, compared to controls. Except for non-volatile metabolite production tests, inhibitory action against V. dahliae was highest. Even the thermostable non-volatile metabolites showed inhibitory effect against both tested pathogens, evidencing that the secondary metabolites of the antagonist have a significant effect on these pathogenic species.
plant pathogens; antagonistic fungus; biological control
