Breeding a New Generation of Cold Hardy Grapevines Tom Plocher, Plocher Vines, Inc. Spring Frost Tolerance 9040 152nd Street N., Hugo, MN 55038 USA Current status: Mid-March warm spells followed by early and mid- [email protected] April cold has caused siginificant bud and trunk injury to some cold www.petitepearlplus.com climate varieties in two out of the last five years. Cultivars with in their lineage tend to lose dormancy during these March warm Seedless Table periods, making them susceptible to April cold. Current State: Cold hardy seedless cultivars such as Approach: Introducing genes from Vitis palmata and Vitis cinerea into Somerset, Petite Jewel, Montreal Blue all suffer from quality my highest quality and hardiest wine selections. Both native defects such as small berries, too small and too compact species show very slow growth in the spring, making them less clusters, or poor berry texture. The challenge is to combine the vulnerable to freezes. I am evaluating a large population of F2 cold hardiness of the Swenson seedless varieties with the seedlings from a 2012 cross of T.P. 3-1-3-N x Petite Pearl. In spring, qualities of fine California and Asian seedless varieties. 2015, some of these started growth 5 days later than Petite Pearl and 19 days later than , , Baltica (graph below shows Approach: April-May, 2015 temps and 50% scale crack dates for various types. • First solve the problem of berry size and cluster size and structure, while retaining good winter hardiness. Daily high temp 2015 Historical average daily high temp • In a second generation, combine these traits with Daily low temp 2015 seedlessness. Historical average low temp Work in Progress: T.P. 2-2-50 and T.P. 3-2-46-S were selected for having the desired cluster structure and size (300-450g) and good berry

form and texture. They are seeded grapes, but have Degrees Fahrenheit seedlessness in their parentage. Also they have shown good April May winter hardiness. TP 2-2-50 had a normal crop from primary buds following the record cold winter of 2013-14. T.P. 3-2-46-S had a crop from secondaries. Both are extremely healthy, vigorous, productive seedlings. Starting in 2015, these two selections are being crossed with seedless varieties including Swenson’s, the Arkansas varieties Gratitude and Jupiter, and USDA’s .

T.P. 3-1-3-N T.P. 4-3-26 (E.S. 10-18-06 x T.P. 3-1-3-N x Petite Pearl Vitis palmata pollen mix) Improving Winter Hardiness Current State: The bud injury we observed over the past five winters can be attributed to: • prolonged severe midwinter cold, as we experienced in January, T.P. 2-2-50 T.P. 3-2-46-S 2013, • extreme low temperatures early in the winter, such as the -24oC (- E.S 5-4-16 x E.S. 6-4-47 MN 1094 x 9307 12oF) incident on 14 November, 2014 and • extreme warm temperatures during late winter (highs of 19-26oC Wine Grapes-Breeding Goals (65-80oF) from 10-24 March, 2012 and for a shorter period in • Hardy to -40oC with no protection March, 2015) followed by cold early spring temps. • Resistant to late winter wam spells The lesson from this is that we still have to strive for greater winter • Late budbreak and slow growth in springtime hardiness. Not only better midwinter hardiness, but even more importantly, better tolerance to early and late winter extremes. • Early ripening: < 1400 DDC of heat; < 160 days growing season • Cluster > 100 g Work in Progress: Backcrossing my best red wine selections with the super hardy • No labrusca or riparia flavors cultivars that gave rise to them. Backcrossing is across breeding iines. • Chemical composition suitable for production of well-balanced • MN 1094 progeny such as Crimson Pearl and Petite Pearl wine: backcrossed to E.S. 10-18-06 - Total acidity < 0.8% and pH ~ 3.35 to 3.45 • Troubador progeny such as Verona and TP 1-1-12 backcrossed to - Sugar = 23-24% E.S. 10-18-06 and MHND2009 4-1 (a new North Dakota selection) - High portion of polyphenols as tannins • E.S. 10-18-06 progeny such as T.P. 2-3-51 backcrossed to DM 8521-1 and Petite Pearl. Evaluating a large seedling population from 2010 cross of T.P. 1-1-12 Special thanks to my three nursery distributors, Bevens Creek Nursery, Northeastern x Petite Pearl. Some select seedlings from this cross survived the Vine Supply, and A&M Vines. Also thanks to my collaborators who second test severe mid-winter challenge of the 2013-14 winter and the 14 promising seedlings: Bear Creek Winery (Fargo, ND), Carlos Creek Winery o o (Alexandria, MN), Blackhoof Creek Winery (Barnum, MN), Shelburne Winery November, 2014 -24 C (-12 F) challenge. Most of these are being (Burlington, VT), and Jaeger’s Run Vineyard (Delano, MN). evaluated for wine quality this harvest season.