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Frontenac gris is a grape cultivar with bronze-gray ("gris" in French) colored fruit suitable for white wine production. Frontenac gris was originally identified as a sport of Frontenac, a cultivar with black fruit that was introduced from the University of Minnesota grape breeding program in 1996. Like Frontenac, Frontenac gris has excellent cold hardiness and disease resistance, together with very good productivity and wine quality.
Origin. Frontenac gris originated as a single cane sport on a plant of Frontenac growing at the University of Minnesota Horticultural Research Center. The single cane was first observed with fruit in 1992. Subsequently plants were propagated from this cane and have all produced gray rather than black fruit. Frontenac was derived from a cross between the French hybrid cultivar Landot 4511 and the University of Minnesota Vitis riparia selection #89, found growing wild near Jordan, Minnesota.
Plant traits. Frontenac gris vines are identical to those of Frontenac. They are "grower-friendly" due to their winter hardiness, disease resistance, strong vigor, desirable growth habit, and high yield potential. Frontenac gris has proven sufficiently cold hardy for consistent production in central Minnesota where temperatures frequently reach -30°F when good viticultural practices are used . Outdoor and laboratory freezing tests have shown it to be more cold hardy than Marechal Foch and Seyval Blanc.
Fruit traits. The clusters of Frontenac gris are loose and medium in size, averaging 131 g/cluster and 18 cm (7 in) in length, and conical in shape with a small shoulder. Berries are small to medium averaging 1.1 g/ berry and 12 mm (0.5 in) in diameter. Sugar levels have been high, averaging 25.6° brix but reaching levels as high as 28° brix. Acid levels have also been higher than most cultivars at 13.7 g/l. Due to these high levels of both sugar and acidity, Frontenac gris wines often require leaving residual sugar in order to produce a well balanced wine in northern climates.
Frontenac gris juice frequently exhibits a slight pink or peach coloration derived from the lightly pigmented skin of the fruit. The juice can be fermented to produce either white table wine or dessert wine. The wine tends to have good body and pleasant aromas, with very little of the herbaceous qualities associated with V. riparia and many interspecific grape hybrids. The most common aroma component identified by tasters has been peach, but apricot, citrus, and tropical fruit aromas have also been noted. "Foxy" aromas characteristic of V. labrusca have not been detected.
Adaptation. Frontenac gris should be a useful variety in other cold climate viticulture areas (USDA plant hardiness zones 4 and 5) of the eastern US and Canada where Frontenac has already become established.
