In vitro Inhibitory Potential of Trichoderma Species on Fusarium oxysporum f.sp vasinfectum the Causal Organism of vascular wilt of Cotton (Gossypium hirsutum l.) in the Nigerian Sudan Savanna

The purpose of this study was to determine the inhibitory potential of three species of Trichoderma namely; Trichoderma asperelum, Trichoderma viride and Trichoderma harzianum on Fusarium oxysporum f.sp vasinfectum (fov), the causal organism of vascular wilt in cotton. The experiment consisted of dual culture incubated at 250C + 10C on PDA, for 9 days. During the experiment, the three trichoderma species were obtained from the soil while the fusarium oxysporum isolate was obtained from IAR, Zaria, Nigeria. Antagonistic activity testing was determined using percentage inhibition of Fusarium oxysporum radial growth. The study's results revealed that all the three Trichoderma species tested in this experiment had significantly inhibited the mycelial growth of fov at different degrees compared with untreated control. The percentage inhibition ranged from 54% for Trichoderma. asperelum, 62.8% by Trichoderma viride to the highest being 75.6% and a mean of 45.50% due to Trichoderma harzianum. These results showed that Trichoderma harzianum was the most effective followed by Trichoderma viride and lastly Trichoderma asperellum. This suggest that there are some similarities between the three isolates of Trichoderma as all the three species could inhibit the growth of Fusarium oxysporum f.sp vasinfectum but the best to be used as bio-control agent for vascular wilt of cotton caused by fov was Trichoderma harzianum pending further research.