Assessment of the Susceptibility of Grapevine Genotypes in the Eastern Anatolia Region Genetic Resource Plot to Powdery Mildew (Erysiphe necator) Under Natural Infection Conditions

Powdery mildew disease caused by Erysiphe necator is an economically important disease of grape varieties of the Vitis vinifera species worldwide. The use of resistant grape varieties in the control of the disease is extremely important for human and environmental health. In this study, the tolerance levels of 203 local cultivars, two tolerant (Regent and Kishmish Vatkana) and two sensitive (Karaerik and Italia) cultivars collected within the scope of the Eastern Anatolia Region Grapevine Genetic Resources Project were determined against the pathogen Erysiphe necator under natural conditions. A visual scale based on sporulation density and necrosis formation on the leaves was used for evaluation and four vines were evaluated for each genotype. The colonisation rate on the surface of the leaves was determined according to the scale values between 0-7. The severity of the disease was calculated based on the lesions on the leaves and the susceptibility of the genotypes was determined. As a result of the study, 3 of the genotypes were highly resistant (HR), 44 were resistant (R), 68 were susceptible (S) and 88 were highly susceptible (HS) in terms of powdery mildew disease severity. Among these genotypes, 50 out of 197 genotypes belonging to Vitis vinifera species and all Vitis labrusca genotypes showed tolerance below 30% in terms of disease severity. Vitis vinifera subsp. sylvestris (Sarmalık Üzüm) was classified as susceptible with a disease severity of 37.99%. In the study, V. vinifera showed more sensitivity than other species. The most resistant genotype was Izabelle-1 (3.88%) and the most susceptible genotype was Beyaz Üzüm S1 (90.07%).