Heavy rainfall in Turkey’s northern Black Sea Region in spring and autumn, combined with insufficient sunshine during the vegetation period, results in poor ripening of European grape ( Vitis vinifera L.) cultivars. Compared to other coastal provinces in the Central and Eastern Black Sea Region, Samsun receives relatively little rainfall. This study evaluated the adaptation of Vitis vinifera L. and Vitis labrusca L. grapes to Samsun by examining the phenology and ripening characteristics of these cultivars in 2010 and 2011 and calculating climatic indices using long-term data for Samsun in order to assess the potential for viticulture in the area. The following climatic characteristics were identified: annual sunshine duration, 1 836 hours; Branas Heliothermic Index (BHI), 3.0; Hydrothermic Index (HyI), 4 053.7°C mm; Winkler Index (WI growing degree days) 1 832/Region III “Warm”; and Huglin Index (HI) 1 978°C/HI-1 “Temperate”. Phenological cycles (budburst to harvest) varied between 120 and 176 days, with Trakya İlkeren and Yalova İncisi the most precocious varieties and Favli the latest variety in both years. Heat summation requirements ranged from 1 210 to 1 844 GDD, with Trakya İlkeren requiring the least and Narince the most heat summation. Total soluble solid (TSS) values ranged from 15.1 °Brix (Trakya İlkeren) to 21.4 °Brix (Labrusca). Although Favli was the last to ripen, the TSS value for this variety was only 17.1%. These findings indicate that, with the exception of Favli, all the varieties examined are capable of maturing under the climatic conditions in the study area, suggesting that the coastal areas of Samsun province are suitable for early and mid-season Vitis vinifera L. grape viticulture.

Extreme winter temperatures during the 2018–2019 dormant season contributed to trunk collapse and complete trunk death of numerous genotypes throughout a diverse grapevine planting in eastern North Dakota, USA. Through the early portion of the dormant season, 12 genotypes were screened to identify lethal temperature exotherms of primary buds; from these results, none were anticipated to be fully prepared to survive the −37 °C minimum temperature recorded in the region. Trunk collapse, death, and survival were monitored for 35 replicated genotypes. New trunks were retrained from suckers and monitored for growth following trunk removal. Only five genotypes exceeded 50% trunk survival at the end of the 2019 growing season, ‘Valiant’, ‘King of the North’, ‘John Viola’, ‘Baltica’, and ‘Bluebell’. Following re-establishment, ‘La Crescent’ was the most vigorous genotype with the largest sucker circumference, sucker length, and internode length. Nearly all genotypes evaluated produced suckers with lengths approaching the high-wire trellis height (1.8 m), designating their potential for cordon retraining in 2020. Cumulatively, however, the lethal temperature exotherm results and the trunk survival examination indicate a harrowing need for investigation of new management practices (such as protected training systems) and the generation of new cold-hardy genotypes to enhance productivity under standard unprotected systems.

A total of fourteen diverse, interspecific hybrid grapevines (Vitis spp.) were evaluated for their adaptability to North Dakota winter conditions using differential thermal analysis (DTA) of low-temperature exotherms (LTE) and bud cross-sectional assessment of survival techniques. This research was conducted in two vineyard locations in eastern North Dakota. This work demonstrates the use of DTA for monitoring and selecting cultivars capable of withstanding sub-zero temperatures. These results were assessed for quantitative genetic traits. High heritability was observed for bud LTE traits and may thus be a useful target for cold hardiness breeding programs; however, it is necessary to ensure that variance is reduced when pooling multiple sample events. After DTA sampling, grapevines were assessed for survival of primary and secondary dormant buds using cross-sectional visual evaluation of death. ‘Valiant’ had the greatest primary bud survival (68%), followed by ‘Frontenac gris’, ‘Crimson Pearl’, and ‘King of the North’. These varieties are among those with potential for production in eastern North Dakota’s environment. The newly evaluated relationships between traits and the heritability of DTA results provide valuable tools to grapevine breeders for the development of cold-tolerant genotypes for future climatic challenges.