Investigation of the possibilities of biological controlagainst alternaria spp, caused by early leaf blight diseasein tomato

Alternaria solani is the cause of early blight disease, which is seen in tomato cultivation areas all over the world and causes significant losses in production. This pathogen causes disease at every stage of plant development and affects almost every part of the plant. The most effective way to control this pathogen is the use of fungicides. However, there has been an increased development of resistance to the two main groups of fungicides, QoIs and SDHIs, due to their frequent use to control early blight. Therefore, in our study, some Chaetomium spp., Trichoderma spp. and nonpathogenic Fusarium oxysporum in biological control were investigated. First of all, 30 Alternaria isolates collected from Samsun province and its districts were subjected to pathogenicity test. Four isolates that were determined to be pathogenic were examined in in-vitro trials in terms of their potential to be used in biological control. The highest inhibition rate in isolate number 10 of Alternaria sp. was achieved by Trichoderma isolates 37 and 39 with 79.5%. Against Alternaria sp. isolate number 12, Chaetomium isolates 26, 28 and 27 showed the highest inhibition at 56.6%, 52.5% and 51.6%, respectively. By taking the two different Alternaria spp. isolates with the highest pathogenicity and the isolates found most effective in the dual-test, pot trials were conducted with a sensitive tomato variety H2274 cv for biological control potential and similar results were obtained with the results obtained from the dual test. It has been concluded that isolate of Chaetomium sp., Trichoderma sp. and T. hamatum has the potential to be used as a biological control agent against Alternaria spp. in tomatoes. It is thought that it would be appropriate to conduct further studies under field conditions and to molecularly identification study the species of Alternaria, Chaetomium and Trichoderma isolates.