Cold resistance division based on leaf tissue structure of early-fruiting walnut cultivars

Abstract：To study cold resistance of early-fruiting walnut cultivars, 14 early-fruiting varieties were used as experimental materials, and 10 leaf tissue structure indexes were observed by using blotting methods and paraffin section methods. Leaf tissue structure indexes were screened via coefficient of variation, analysis of correlation and hierarchical cluster analysis, and comprehensive evaluation on cold resistance for each variety was done by subordinate function. The results showed that leaf thickness, stomata density and the ratio between palisade tissue and spongy tissue were the main factors related to the hardiness ;the cold resistance for 14 cultivars was in order of Xilin No. 2〉Chico〉Wen185〉Vina〉Chandler 〉Liaohe No. 3〉 Tulare 〉Luguang〉Liaohe No.4〉Xifu No. 2〉Zhonglin No. 5〉Xiangling〉Xilin No. 3〉Liaohe No. 1;ac- cording to the cold hardiness, the cultivars could be divided into 5 groups： Xilin No. 2 with high cold re- sistance; Chico and Wen185 with cold resistance ; Chandler, Vina, Luguang, Tulare, Liaohe No. 3 and Liaohe No.4 with medium cold resistance ;Xifu No. 2, Zhonglin No. 5 and Liaohe No. 1 with low cold-tol- erance; Xiangling and Xilin No. 3 without cold resistance.