Cold-Hardiness Evaluation of Grapevine Buds and Cane Tissues

摘要

A system for differential thermal analysis (DTA) was constructed to assess cold hardiness of grapevine buds and cane tissues. This updated system incorporated a sample chamber of our own design with a commercially available programmable freezer and data acquisition system (DAS). Thermoelectric modules (TEM) were used to sense exotherms that are produced when water or tissues freeze. The TEM signals recorded by the DAS at 15 sec intervals were downloaded directly to an Excel spreadsheet. The DTA system was designed to test up to 35 samples of five buds or three canes per TEM simultaneously. Bud and cane low temperature exotherms (LTE) recorded by this system correlated very closely with those of a standard system, and the extent of cane phloem and xylem injury, based on tissue browning, corresponded well with expected injury based on LTE analysis. The LTEs of moist buds were 3℃ to 4℃ higher and those of moist canes 2℃ higher than LTEs of corresponding dry tissues, indicating that surface moisture increases the susceptibility to cold injury. Cold hardiness of eight grape cultivars increased from late fall through mid-January, after which buds and canes began to deacclimate. Riesling was the hardiest of all cultivars tested. Chardonnay reached similar levels in midwinter, but was considerably less hardy in late fall and late winter. Pinot gris and Viognier were the least hardy among the white winegrape cultivars. Among red winegrape cultivars, Cabernet Sauvignon was generally the hardiest and Merlot the least hardy, with Malbec and Syrah being intermediate.