Biocontrol potential of Trichoderma harzianum in controlling wilt disease of pistachio caused by Verticillium dahliae

wilt caused by , is one of the most devastating diseases in pistachio orchards in the world including Iran. In search for an effective non-chemical strategy for the management of this disease, we evaluated the biocontrol potential of isolates obtained from the rhizosphere of healthy pistachio trees in different locations of the Kerman province of Iran against under laboratory and greenhouse conditions. Dual culture tests in the laboratory were conducted in a completely randomized design using 72 isolates. Twenty isolates showed the highest antagonistic activity. The results indicated that all 20 isolates were capable of inhibiting the mycelial growth of significantly. Among them, isolates Tr8 and Tr19 were the most effective by 88.89% and 85.12% inhibition, respectively. Extracted cell free metabolites of all effective isolates also inhibited the growth of in the culture medium significantly. According to the results, isolates Tr4 and Tr6 inhibited fungal pathogen growth by 94.94% and 88.15% respectively, through production of non-volatile metabolites. In the evaluation of volatile metabolites, isolates Tr5 and Tr4 were the most effective by 26.27% and 24.49% growth inhibition, respectively. Based on the results of the experiments, the five most effective isolates were selected for evaluation under greenhouse conditions for their biocontrol potential in controlling wilt of pistachio. Results of the greenhouse, ( ) experiments were positive and indicated that the occurrence of wilt disease in plants treated with the antagonists alone or in combination with pathogenic fungus was lower than in plants inoculated with pathogen alone. The overall results of this study suggest that fungal antagonist may be an effective biocontrol agent for the control of wilt of pistachio.