Antagonistic potential of Trichoderma species in controlling Fusarium oxysporum f. sp. vasinfectum, the causal agent of cotton wilt

Variations in the antagonistic activity of five species of Trichoderma, T. polysporum, T. koningii, T. pseudokoningii, T. viride and T. harzianum, were evaluated in vitro and in situ, against Fusarium oxysporum f. sp. vasinfectum, the causal agent of cotton wilt. Al the species of Trichoderma behaved as antagonic to Fov in dual culture tests to varying degrees. T. polysporum was the most active. The mechanism of antagonism was mainly by vacuolation and cellular plasmolysis. However, T. harzianum was able to wrap around Fov hypha, and together with T. pseudokoningii, penetrated Fusarium mycelia. Among the species of Trichoderma, T. polysporum and T. viride were responsible for the highest reduction of the pathogen conidium germination, when incubated in Armstrong liquid medium at 26 degrees C. T. harzianum, T. koningii e T. viride were the most effective in suppressing Fusarium wilt of cotton seedlings.