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Poster: Biology & Disease Mgmt: Genetics of Resistance


Disease susceptibility screening for cold-climate wine grape cultivars
D. JONES (FORMERLY SCHREINER) (1), P. McManus (2) (1) University of Wisconsin, Madison Dept. of Plant Pathology, U.S.A.; (2) University of Wisconsin Madison Dept. of Plant Pathology, U.S.A.

The wine grape industry in the Upper Midwest has expanded rapidly in the past 15 years. Inconsistent reports on disease susceptibility in cold-climate wine grape cultivars may be leading to overspraying and underutilization of host resistance in the region. Inconsistencies in reports may stem from a lack of study on adult plants in a randomized, replicated, and fungicide free vineyard environment. Two vineyards containing eight cultivars were left unsprayed by fungicides in 2015. Severity of downy mildew, powdery mildew, and black rot was measured from bud break until 2 weeks post-harvest. There was a significant difference among cultivars for all three diseases at both sites. A second assay was conducted using potted grape vines as “trap plants” to capture inoculum present in the field and gain further information on disease susceptibility. Using trap plants and artificial humidification did not generate results consistent with the disease severity and progress observed in the field during the growing season. These preliminary data suggest that selection of certain cultivars has the potential to reduce sprays needed to manage diseases during the growing season in the Upper Midwest. Results further indicate differences exist between foliar and fruit susceptibility for all three diseases, a distinction that is not made in current rating systems. This work will continue in 2016 to gain additional susceptibility data and observe differences between growing seasons.