Cold damage is a threat to grapegrowers worldwide. Cold hardiness varies across Vitis vinifera cultivars, but the influence of clone and rootstock selection on this trait is unclear. Five clone x rootstock combinations of Riesling (clone 49 x Riparia Gloire (RG); 49 x SO4 Teleki; clone 239 x RG; 239 x SO4; 239 x Couderc 3309) and four clones of Sauvignon blanc (clone 242, 297, 376, and 530 on SO4 Teleki rootstock) were evaluated over three dormant seasons (2016/17, 2017/18, and 2018/19). Bud cold hardiness was quantified every two to four weeks by differential thermal analysis (DTA) and reported as low temperature exotherms (LTE). Yield and pruning weights were recorded every year. Rootstock did not consistently influence the cold hardiness of Riesling buds, although clone 239 was generally hardier than clone 49. Significant clone*rootstock interactions were observed more frequently in the first year of the study. No

Winter survival of Vitis vinifera Linnaeus in cool climate viticultural areas can be jeopardized due to inadequate cold hardiness. Dehydrins are a family of proteins commonly found in plant tissue in response to dehydration stress and cold exposure. To determine their presence and relationship to cold hardiness in overwintering grapevines, compound buds of V. vinifera cv. Sauvignon blanc were sampled from a commercial vineyard every two to three weeks throughout the 2016-2017 winter. Proteins were extracted and separated by SDS-PAGE, and potential dehydrins were immunoblotted with a commercial antibody raised against the dehydrin K-segment consensus sequence. Six protein bands were identified in four Sauvignon blanc clones at 23, 26, 35, 41, 48 and 90 kDa, showing a serological relation to dehydrins due to their reaction with the K-segment antibody. The bands at 23, 41, 48, and 90 kDa were confirmed as dehydrins following trypsin digestion and LC-MS/MS with Mascot analysis. Their fluctuations throughout the dormant season were quantified by immunoblotting and three patterns emerged: the 23, 26 and 35 kDa proteins peaked immediately prior to deacclimation; the 41 and 48 kDa proteins peaked during maximum hardiness and decreased towards deacclimation while the 90 kDa plateaued during the same period. Maximum hardiness and relative dehydrin band intensity were positively correlated (p < 0.050) for all but the 23 kDa protein. The variation in accumulation patterns and relationships to cold hardiness indicates that these dehydrin proteins are likely regulated by different molecular processes and could play different roles in cryo-protection throughout dormancy.