Antagonistic activities of bioagent fungi Trichoderma harzianum and Pleurotus ostreatus against three species of Fusarium in cucumber plants

Many bioagent fungi have promising potential as eco-friendly alternatives to fungicides, with considerable antagonistic activity against various phytopathogenic fungi. The present study aimed to investigate the antagonistic activity of Trichoderma harzianum and Pleurotus ostreatus isolates against Fusarium spp., the causative agents of wilt disease in cucumber plants, through a dual plate assay of volatile and nonvolatile compounds from these bioagent fungi. The results showed significant (P < 0.05) antagonistic activities of T. harzianum against the growth of F. solani AJA2 (62.3%), followed by F. oxysporum AJA (55.2%), F. incarnatum AJA (53.2%), and F. solani AJA1 (50.8%). The effectiveness of P. ostreatus against the four Fusarium species was notably less than that of T. harzianum. In contrast, in the dual culture assay, the bioagent fungal filtrate exhibited inhibitory effects on the growth of all pathogens at 25% concentration. The highest inhibition rate (85%) was shown by T. harzianum against F. incarnatum. The percent of inhibition caused by P. ostreatus was substantially lower than that caused by T. harzianum, which reached 35% in F. incarnatum followed by other pathogens. The volatile compounds of T. harzianum led to a high percentage of inhibition of all the three Fusarium species, while the highest percentage of inhibition due to the compounds of P. ostreatus was observed only for F. solani AJA1 (41.5%). From these results, we concluded that despite the diverse inhibitory effects of both bioagent fungi against Fusarium species, they exhibited successful antagonistic activity and the ability to compete against these species.