İnvestigation of the effectiviness of Clonostachys rosea (Sch.) (Schroers & Samuels on root rot caused by Fusarium solani (March.) Sacc. and plant growth in Pistachio

Pistachio cultivation is crucial for the economy of both our country and the Southeastern Anatolia Region. Some soil-borne pathogens, especially those that cause root and crown rot and wilt diseases, cause significant yield losses in pistachios. Biological control is an alternative control method to chemical control against plant diseases. This study was conducted in Siirt University Phytopathology Laboratory in 2022-2023. The aim of this study was to determine the effectiveness of Clonostachys rosea on root rot and plant development caused by Fusarium solani in pistachio. The material of the study consisted of the Fusarium solani KY1 pathogen isolated from pistachio and LO41, FG8, FG9 and FG10 isolates of Clonostachys rosea. According to the results of the experiment conducted to determine the antagonistic activity through the volatile metabolites formed by C. rosea isolates, it was determined that the most effective isolate, C. rosea FG10, inhibited the pathogen with a rate of 9,04%. According to the results of the experiment conducted to determine the antagonistic activity of C. rosea species against the pathogen by the dual culture method, C. rosea LO41 isolate, which showed the most antagonistic effect against the pathogen, was effective with a rate of 17,20%. In pot studies to determine the effectiveness of antagonists in soil artificially contaminated with F. solani, the disease severity of the positive control F. solani KY1 was determined to be 72,50%. As a result of the application of C. rosea F10, C. rosea F8, C. rosea LO41 and C. rosea F9 antagonists, the disease severity was 20,00%, 27,50%, 37,50% and 52,50%, respectively and the pathogen suppression rates of antagonists are 72,41%, 62,06%, 48,27 and 27,58%, respectively. Thus, the most effective antagonist was determined to be C. rosea F10. According to the results of the experiment conducted to determine some morphological development parameter values of pistachio seedlings, it was observed that plant development was better than the control. According to the results of the measurements, it was determined that the isolate that showed the best growth in both root and stem length and plant fresh weight was C. rosea F10, and the isolate that showed the best growth in plant dry weight was C. rosea F8. Thus, biological control possibilities of C. rosea against F.solani, an important soil pathogen in pistachio, were investigated.