Freezing Tolerance of Vitis vinifera Cultivars New to Northeastern United States

Grapes are temperate crops and are most frequently damaged by freezing temperatures.  The severe economic losses that result from the freezing injury continue to be a major constraint to the growth of the grape and wine industries in cold regions. The long-term goal of this project is to identify cultivars that are adapted to the weather conditions in Northeastern United States. In this study, the freezing tolerance (FT) of more than 20 Vitis vinifera cultivars was determined at two sites for two seasons in Ohio. Buds were collected periodically between September and April and then subjected to controlled freezing tests. FT was determined by thermal analysis and expressed as LT50 in ^oC (temperature that kills 50% of the primary buds). The maximum bud FT (minimum LT50) was reached in December-January and ranged between LT50 = -15 ^oC (‘Durif’, most cold-sensitive) and LT50 = -25 ^oC (‘Gamay noir’ and ‘Pinotage’, most cold hardy). The rates of cold acclimation (transition from a cold sensitive to a cold hardy) and deacclimation (transition from a cold hardy to a cold sensitive state) for each cultivar were also estimated and showed cultivar differences. It is concluded that the knowledge of freezing tolerance of each cultivar reported in this study will aid growers make objective decisions on cultivar selection in cold regions.