Sarah Bogenrief,* Venkateswara Kadium, Andrej Svyantek, Collin Auwarter, and Harlene Hatterman-Valenti
*North Dakota State University, 1340 Administration Ave, Apt 201, Fargo, ND 58105 (sarah.m.bogenrief@ndsu.edu)

Cold hardiness is a limiting factor for many perennial fruit crops of North Dakota. Further understanding of Vitis cold hardiness is critical for prolonged survival of wine- grape production in northern latitudes. Compounding stress on vines from bud dam- age, disease, winter injury, and herbicide drift can ultimately reduce or eliminate cold hardiness, leading to vine death. Crop loss due to unpredictable weather and loss of cold hardiness is an inevitable hardship of the fast-approaching future. Six interspecific Vitis hybrids were evaluated for bud cold-hardiness using differential thermal analysis (DTA). Field samples were taken throughout dormancy from two vineyards, then slowly frozen to measure low temperature exotherms (LTEs) related to super-cooling and intracellular freezing in grapes. Phenological data of cultivars is recorded using the BBCH identification scale and evaluated for survival. Across two winters, temperature and estimated cold hardiness trends have showed increased hardiness as temperature decreases. Cultivars at both locations showed less hardiness than reported in previous studies, subsequently exhibiting winter injury and bud death. Most importantly, reduced and eliminated crop load was observed in this study, likely due to bud death and decreasing vine health. Results of this research will be pivotal for promoting sustainability in North Dakota vineyards, determination of vineyard site location, hardy cultivar selection, and future breeding decisions.

Funding Support: North Dakota Department of Agriculture