Verticillium wilt of potato is a major limiting factor in potato production. In this study, a total of 14 biocontrol agents, consisting of seven different species (Trichoderma harzianum, Trichoderma deliquescens, Fusarium oxysporum, Talaromyces flavus, Bacillus subtilis, Pseudomonas fluorescens and Serratia marcescens) were examined against Verticillium dahliae the causal agent of potato wilt in vitro and greenhouse conditions. Antagonistic effects were evaluated through volatile and non-volatile metabolite productions in vitro. All antagonists caused significant reduction in growth of V. dahliae compared to the control. The maximum antagonistic effect was observed in isolates of T. flavus with inhibition zones ranging from 65.4 to 66.7% by dual culture method. The ability of biocontrol agents varied in production of siderophore, protease, cyanide hydrogen and indole acetic acid. Results of the greenhouse study 75 days after sowing indicated that all biocontrol agents reduced disease severity and vascular discoloration of Verticillium wilt at different rates. Accordingly, Trichoderma flavus TFPV24 was the most effective in reducing disease severity and vascular discoloration of potato Verticillium wilt by 76% and increasing yield by 171% compared to the untreated control. In general, in both in vitro and greenhouse assay, isolates of T. flavus were the most effective antagonist and Serratia marcescens has the least antagonistic effect. The overall results of this study showed that isolates of T. flavus have high efficacy in controlling potato Verticillium wilt.
