Seasonal Changes in Low Temperature Resistance of Grape Buds

Abstract

Fifty 5-bud samples were taken from selected Vitis labrusca L. cv Concord and Vitis vinifera L. cvs White Riesling (WR) and Cabernet Sauvignon (CS) vines weekly over a seven-year period to test cold acclimation of primary buds. Samples were placed in a cold box at 0°C programmed to lower the temperatures 3°C per hour to simulate winter temperature drop to determine the killing temperature of buds. Temperature required to kill half the buds (T₅₀) was determined.

A stable T₅₀ value for primary buds during dormancy was -26°C for Concord and -23°C for WR and CS. Cold weather (maximum temperature below -1°C) preceding testing resulted in increased cold resistance. Primary buds reached an estimated T₅₀ of -40°C for Concord, -37°C for WR, and -31°C for CS in January 1979. Concord retained its minimum hardiness level one to two weeks less than the two vinifera varieties.