Abstract: Winter freezing injury is one of main limiting factors restricting the development of wine grape cultivation in northern China, which seriously affects the growth, development, yield, and quality formation of wine grape in the northwest inland with soil buried for winter protection. As the necessary channel for exchanges of nutrient and water, root collar is located at the junction between aboveground and underground, as well as that of soil and atmosphere. Root collar is sensitive to environmental changes because it suffers drastic changes of temperature. In this study, we examined the cold resistance of the wine grape tree ‘Cabernet Sauvignon’ planted in the eastern foothills of Helan Mountain in Ningxia. Root collar, primary lateral root, secondary lateral root and fibrous root of wine grape tree were divided into upper, middle and lower parts, respectively. The supercooling point, freezing point, relative electrical conductivity and water content of roots were measured in the process of simulated natural low temperature freezing. The cold resistance of wine grape root neck and different parts of roots were evaluated by fuzzy membership function method and cluster analysis. There were significant differences in cold resistance among different parts. The cold resistance of root collar was the strongest. The cold resistance of upper part of the primary lateral root was stronger than that of the secondary lateral root. The cold resistance of the middle and lower part of the primary lateral root was similar to that of the corresponding part of the secondary lateral root. The cold resistance of fibrous root was the weakest. The upper part in root collar, primary lateral root, secondary lateral root and fibrous root showed the strongest cold resistance, followed by the middle part and the lower part. The results of cluster analysis showed that the tested roots could be divided into three categories: (1) the upper and middle part of the primary lateral root with strong cold resistance; (2) the lower part of the primary lateral root, the upper and middle part of the seco〖HJ*4〗nd lateral root, the upper and middle part of the fibrous root with moderate cold resistance; and (3) the lower part of the fibrous root with weak cold resistance. Our results are of great significance for monitoring, early warning anddefense of root collar and root winter freezing injury in wine grape.

Key words: Cabernet Sauvignon, root collar, cold resistance, cluster analysis, semi-lethal temperature.