Resistant to late spring coldness of wheat is closely related to its own development process and the internal physiological indexes at low temperatures. In order to screen the indexes of spring cold resistance of wheat varieties and establish corresponding evaluation methods of wheat resistant to late spring coldness, 11 wheat cultivars including Zhengmai 7698, Aikang 58, Shimai 19, and other 8 representative varieties in Huanghuai wheat region were selected as experimental materials. After low temperature treatment of the test materials for 6, 12 and 18 h in the artificial climate chamber during the wheat double ridge stage, floret differentiation stage, stamens and pistils differentiation stage, anther connective stage and tetrad stage, the cold damage level of young spikes was observed, and the contents of soluble sugar, soluble protein, and malondialdehyde(MDA), and activities of superoxide dismutase(SOD) and catalase(CAT) in each variety were determined. Besides, the grain yield and its components of wheat varieties at anther connective stage were analyzed under low temperature stress. The results showed that the cold damage level of young spikes at double ridge stage and anther connective stage was the lowest and the highest. Physiological indexes of wheat leaves after low temperature treatment at other four stages were further studied, the result showed that the average decrease of soluble sugar content, CAT activity and SOD activity of each variety after low temperature treatment for 18 h at anther connective stage was significantly higher than that of other three stages, with a decrease rate of 32.33%, 38.22% and 45.20%, respectively, and the average increase of MDA content was significantly higher than that of other three stages, with an increase rate of 84.73%. The correlation analysis demonstrated that the cold damage level of young spikes was highly significantly correlated with the amplitude of soluble sugar content, SOD activity and MDA content after 12 h of low temperature treatment at anther connective stage. In conclusion, the anther connective stage was the most proper growth stage for the identification of wheat resistance to late spring coldness, and the soluble sugar content, SOD activity and MDA content can be used as physiological indexes for the identification of wheat resistance to late spring coldness. The cold resistance in spring of different varieties was evaluated based on the comprehensive values of the fuzzy mathematics method of the above three physiological indexes, which were 0.65<D≤1.00, 0.40<D≤0.65 and 0.00<D≤0.40, corresponding to cold-resistant levels of strong, medium and weak, respectively. |