Evaluation of Primary Bud Freezing Tolerance of Twenty-three Winegrape Cultivars New to the Eastern United States

Abstract

Plantings of Vitis vinifera L. cultivars have increased significantly in the eastern United States due to market demand for their wines. However, V. vinifera is a cold-sensitive species and planting new cultivars of unknown cold susceptibility in cold areas has resulted in frequent winter damage and crop loss. It is the purpose of this study to determine the freezing tolerance of 23 winegrape cultivars predominantly grown in Europe and South Africa and to compare three statistical methods [mode-date, piecewise regression, and annual mean LT50 (AFT)] for determining the minimum low temperature that will kill 50% of primary buds (LT50). Primary bud freezing tolerance (FT), expressed as LT50 in °C, was determined biweekly over three dormant seasons under field conditions in Ohio. Minimum LT50 was most accurately determined using the AFT method. AFT provided a lower error estimate than mode-date or piecewise regression and best corresponded with the percentage of vines that survived exposure to the polar vortex freeze events of 2014. The two-year average AFT ranged from −19°C for Gamay noir to −15°C for Barbera and distinguished a 1°C difference among cultivars in primary bud FT. We proposed to express cultivar AFT relative to a standard cultivar grown in the same location (Merlot in this study), termed RAFT. The results from this study can be used to assist selection of V. vinifera cultivars suitable for vineyard sites where freezing temperatures limit winegrape production.