Susceptibility of some grapevine cultivars to downy mildew disease(Plasmopara viticola)

Turkey is one of the most important countries in the world with its vineyard areas. However, one of the diseases encountered almost every year in grape production and causing significant yield losses is downy mildew. In this study, the susceptibility levels of the varieties used in grape cultivation in the vineyard areas of BUU Faculty of Agriculture were determined. The susceptibility levels of cultivars to downy mildew disease were determined by evaluating the disease severity with natural inoculum on a 0-4 scale under field conditions. The experiment was planned as 4 blocks and 4 repetitions for each block, according to the randomized blocks design, and each replication consisted of a vine. Varieties evaluated in the study were Michel Palieri, Cardinal, Italia, Trakya İlkeren and Hamburg Misketi. The study was carried out during the production period of 2020, and disease severity differences between cultivars were found most significantly in the mid-June evaluation. In the study, it was determined that the severity of downy mildew disease in Vineyard differs according to the cultivars and the cultivars most susceptible to the disease were Trakya Ilkeren (81.87%) and Michel Palieri (72.81%). Disease susceptibility levels of other cultivars were determined as 44.93% for Cardinal, 36.43% for Hamburg Misketi and 28.93% for Italia. During the growing season, no fungicide application was made and the levels of the disease was discussed with the records of the weather conditions and leaf wetness periods effective on disease development. It was determined that the rate and severity of downy mildew disease decreased in all cultivars with the increase in air temperatures. It was determined that the differences in susceptibility between cultivars decreased with the decrease in disease severity. In the evaluation made at harvest time, the susceptibility levels of the cultivars to the disease were determined as 19.06% for Trakya Ilkeren, 18.25% for Michel Palieri, 14.69% for Hamburg Misketi, 12.69% for Cardinal and 12.25% for Italia.