Investigation of drying of tree caused by soil-borne pathogens in pistachio fields of Southeastern Anatolia region

In this thesis, some soil-borne fungal pathogens causing drying were investigated in pistachio production areas in the Southeastern Anatolia Region. 1.900 trees were observed in June and September of the 2021 growing season in 48 different pistachio orchards in Gaziantep, Şanlıurfa and Kilis provinces. Survey studies showed that the highest disease severity and disease prevalence were determined in Şanlıurfa with 11.4% and 94.4%, respectively, and the highest disease rate in Gaziantep with 23.1%. Within the scope of the study, samples were taken from the roots and stems of the trees with signs of drying, and the diagnosis of the disease was made with classical and molecular methods. At the end of the study, 22 different fungal species were isolated. Clonostachys rosae was the most common with 73.3% in the isolations made in the root region, and Fusarium spp species was determined the most with 44.2% in the isolations made from the stem. The 12 of the 22 fungal species obtained were inoculated to UCB-1, Buttum, Pistacia vera L. rootstocks in pathogenicity studies. In pathogenicity studies conducted with 12 pathogen species selected from 22 isolated fungal species, UCB-1, Buttum, P. vera genotypes rootstocks were inoculated. As a result of the pathogenicity study, the largest areas of infection; Fusarium oxysporum on UCB-1 rootstock, Nectria sp. on P. vera rootstock, Alternaria alternata on Buttum rootstock (26 mm², 21 mm², 29 mm², respectively). To conclude, it was revealed that due to the fact that a significant part of the isolated fungi were weak parasitic pathogen and the infection areas they create were limited. The isolated factors may not be the cause of drying of tree alone, and the weakness parasitic fungi cause damage with the use of faulty cultural processes and incorrect irrigation systems.