Issue link: https://read.dmtmag.com/i/681909
14 JUNE 2016 Good Fruit Grower www.goodfruit.com New white wine grape variety shows resistance to downy, powdery mildew, phylloxera. by Dave Weinstock T he University of Minnesota has announced its newest cold-hardy wine grape variety, and it's one for which north country grape growers have been waiting. Called the Itasca for the lake in northern Minnesota identified as the source of the Mississippi River, the white grape has a lower acidity than other cold-hardy varieties and high sugar, potentially making it an ideal candidate for a dry white wine. The variety also shows resistance to downy and powdery mildew, as well as phylloxera, and it is hardy to USDA's Plant Hardiness Zone 4. Provenance The Itasca has been in development since 2002. Originally tagged as MN 1285, it was created from a cross pollination of Frontenac Gris and MN 1234, a Seyval Blanc offspring known for its resistance to powdery mildew. Two of its ancestors are accessions of Vitis riparia, from which it acquired its high sugar — and its cold-har- diness. In 2014, the winter of the Polar Vortex, Frontenac Gris had a 25 percent bud survival rate, while Itasca endured the same weather and emerged with 65 percent primary bud survival, said Matt Clark, a University of Minnesota assistant professor and grape breeder. Though not certified yet, the variety has been sub- mitted to the Clean Plant Center Northwest in Prosser, Washington. To date, they've done a few performance evaluations with some growers but no large-scale vine- yard or winery trials. The university has licensed three nurseries to sell its new variety for the 2017 season: Winterhaven Vineyard and Nursery in Janesville, Minnesota; Double A Vineyards in Fredonia, New York; and Northeastern Vine Supply in West Pawlet, Vermont. Knight Hollow Nursery of Middleton, Wisconsin, uses a tissue culture for micropropagation. Grower friendly Vines can be vigorous, depending on the soil. The breeders have found vine spacing should be 6 feet apart when organic matter is 2.5 percent or less and 8 feet apart for 3 percent or more. "Irrigation is important for estab- lishment," Clark said. Its growth habit is open and manageable. Shoots can either grow upright or procumbent. "Fruit exposure is good with minor adjustments," he said. The university vines hang on high-wire, double cor- don systems. Clark said he thinks they can be trained to vertical shoot positioning, though it's not been tested yet. Kicker shoots on the trunk can reduce vine growth, and should be pruned off or back to short spurs, he said. Clark said they don't have very good data on when bud break occurs. "It didn't seem to be as early as Marquette, but may be in the same time frame as Frontenac," he said. The fruit ripens earlier than Frontenac, by mid- to late September. Cluster structure is moderately compact, Minnesota's dry, cold-hardy white Grapes Courtesy John thull Itasca grape clusters weigh from 95 to 145 grams, can be winged or shouldered and show a golden hue at harvest.