Comprehensive evaluation of cold resistance in different parts of four wine grape varieties based on different thermal analysis

Freezing injury is one of the main meteorological disasters for grapes in northern China, and it seriously affects the growth and quality of wine grapes, which are soil-buried for winter protection in the northwest inland zones, and restricts the sustainable development of grapevine and the wine industry. The cold resistance of different parts of wine grape varies with the genetic characters of the grape varieties. In this paper, the cold resistance capacity of different parts of wine grape were measured using different thermal analysis (DTA) technologies to provide a theoretical basis for the prevention and mitigation of the winter freezing injury of grape. The physiological response indexes (supercooling point, freezing point, relative conductivity, and water content of branches) of four common varieties of wine grapes, namely, 'Cabernet Sauvignon' 'Merlot' 'Syrah, ' and 'Beimei', were measured by simulating the natural freezing schedule. Based on the fuzzy subordination function, the cold resistance capabilities of four wine grape varieties roots were comprehensively evaluated. The results showed that: 1) there were significant differences in cold resistance among different varieties, but the trend cold resistance of root and branch of the four varieties were identical. The order of cold resistance of the four varieties was: 'Beimei' > 'Cabernet Sauvignon' > 'Merlot' > 'Syrah'. 2) There was a significant correlation between the semi-lethal temperature and the supercooling point of the root system. Combined with the semi-lethal temperature, the temperature range of the supercooling points of the tested varieties roots was -5.2~-2.7 ℃, which could be used as the temperature reference index of the root system of four wine grape varieties. In all parts of the tested varieties, the cold resistance of branch was the strongest, the taproot was the second, the secondary root was the weakest, and the cold resistance capacity of the taproots was significantly better than that of the accessory roots. The results of this study are of significance to the monitoring, early warning, and improving the ability of wine grapes to resist overwintering freezing damage and provide a theoretical basis for the breeding of cold resistance ability in wine grape and the popularization and application of excellent varieties.