Investigation of the effect of Trichoderma pers. on root rot caused by Rhizoctonia solani Kühn. and plant growth in pistachios

Due to reasons such as environmental pollution caused by chemical pesticides used in agriculture, residue problems and the difficulty of chemical control of soil pathogens, alternative methods are being investigated to combat plant diseases. Biological control is a method developed as an alternative to chemical control. Trichoderma species are known to be the most used antagonists in biological control. It is found in nature in almost all soil and natural habitats, and especially in areas containing organic matter. There are mechanisms against plant pathogens such as mycoparasitism, antibiotic production, competition for space and nutrients, and promoting development in the plant. This study was conducted at Siirt University Phytopathology Laboratory in 2022-2023. In order to determine the effectiveness of Trichoderma species against the Rhizoctonia solani pathogen, its effectiveness was determined in the laboratory, through volatile metabolites and by dual culture method. Again, the effectiveness of antagonists was investigated in potting soil artificially contaminated with the pathogen. In addition, some development parameters of clean soil applications were also investigated. As a result, it was determined that the Trichoderma sp.FT1 isolate inhibited the pathogen the most with a rate of 33.88% through volatile metabolites, and the Trichoderma harzianum TUZ16 isolate inhibited the pathogen with a rate of 70.97% in the application made with the dual culture method. Later, the effectiveness of these antagonists against Rhizoctonia solani was investigated in pot studies. In this context, the disease severity of the Rhizoctonia solani pathogen was determined as 75.00% and this pathogen was identified as Trichoderma harzianum TUZ16 (66.66%), Trichoderma virens İB1 (60.00%), Trichoderma viride VG18 (56.66%) and Trichoderma sp. FT1 (43.33%). In addition, the effects of these species on development parameters such as wet, dry weight and height of the pistachio plant were also determined. Considering plant root lengths, the best growing antagonist was T. harzianum TUZ16, and considering stem lengths, the best growing antagonist was Trichoderma sp. FT1 isolate. It was found to be in the Considering the fresh and dry weights, T. harzianum TUZ16 was found to be the best growing isolate. Thus, biological control was carried out against Rhizoctonia solani, which causes root rot in pistachios.