Using differential thermal analysis to analyze cold hardiness in the roots of grape varieties

• LTE was initially used in cold hardiness analysis of grape roots.
• The LT–I was innovatively applied to analyze the LTE of root.
• The reasons for different cold hardiness also obtained a preliminary explanation.

In this study, a system for differential thermal analysis (DTA) was applied for low temperature exothermic (LTE) analysis of the roots of several grape varieties. We determined lethal temperature–injury (LT–I) values of phloem and xylem using a three-point method. We performed a comprehensive evaluation on LT20 to LT80 of different grape varieties using subordinate function value analysis. The result indicate that Beta had the strongest cold hardiness of all the rootstocks examined, followed by SO4, Dogridge, 3309C, 5BB, 101-14M and 140Ru, while 1103P and 110R had the weakest cold hardiness. Of the cultivars tested, Frontenac had the strongest cold hardiness, followed by Golden Queen, Chambourcin and Beck memento, with Summer Black, Merlot noir, Vidal and Riesling exhibiting moderate cold hardiness and Syrah, Carmenere, Dorn felder and Tannat the least cold hardy. We examined the root cross-sectional anatomy and determined the relative water content in 12 varieties with different cold hardiness gradients and performed correlation analysis of the subordinate function values. We found that in grape root tissue, low water content and free water content and high bound water and bound water/free water content resulted in large subordinate function values for LTS, which indicates good cold hardiness. Grape varieties with thick root exodermis layers, thin phloem and a high proportion of xylem had better cold resistance than the other varieties.