Antagonism of Trichoderma isolates against plant pathogens of agricultural interest

Trichoderma fungi are the main pathogens of biocontrol agents used in agriculture. The isolation and in vitro selection of these antagonistic fungi are essential steps in establishing biological control programs and the composition of commercial products. This study aimed to identify, evaluate and select Trichoderma spp. for biological control of plant pathogens of agronomic importance. The antagonist potential of eighteen Trichoderma isolates was tested with Sclerotinia sclerotiorum, Alternariaalternata, Ceratocystis fimbriata, Fusarium oxysporum and Phoma sp. through direct in vitro confrontation tests. The degree of isolate antagonism was assessed according to the criteria of Bell et al. (1982). All isolate antagonists were effective in competing for space and nutrients, with high or intermediate antagonistic action against different species of plant pathogens confronted. There were differences in the biocontrol potential of the same Trichoderma sp. in relation to different plant pathogens, as well as among isolates belonging to the same species. The Trichoderma sp. isolates tested in this work were effective in the in vitro control of Sclerotinia sclerotiorum, Alternariaalternata, Ceratocystis fimbriata, Fusarium oxysporum and Phoma sp.