Study of Antagonistic Effects of Trichoderma Species on Growth of Verticillium dahliae, the Causal Agent of VerticilliumWilt of Pistachio under Laboratory Condition

Verticillium wilt is a serious disease of pistachio caused by Verticilliumdahliae. Control of the disease is difficult due to soil borne nature of the causal agent. Verticillium wilt has been biologically controlled by Trichoderma spp. In the present study, Trichoderma spp. was isolated from soils of pistachio orchards and their effect was investigated on radial growth of Verticillium dahliae by using dual culture and production of volatile and non-volatile metabolites. Five isolates of T. harzianum and one isolate of T. asperellum,T.koningii and T. crassum were used in the present study. All the isolates of Trichoderma produced volatile and non-volatile metabolites that reduced radial growth of the pathogen. T. harzianum 30 and T. koningii isolates had the highest effect on radial growth of the pathogen but T. harzianum 42 and T. crassum showed the lowest effect in non-volatile test. Six days after culture of pathogen on the medium was the best time for study of effect of the non-volatile metabolites. In volatile metabolite test, T. harzianum 85 and T. koningii reduced radial growth of V. dahliae further than others. Overally, T. harzianum 30, 85 and T. koningii isolates showed the highest inhibitory effect of radial growth of V. dahliae.