Analysis of anatomical leaf structure and cold resistance of 12 walnut cultivars in Yunnan province

To study the cold resistence of 12 walnut cultivars planted in Yunnan province，leaf tissue structure indexes were observed by using 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: organizational structure loose degree， spongy tissue and leaf thickness were the main factors related to the hardiness；the cold resistance of 12 cultivars was in the order of: Hartely > Chandler >Yunxin yunlin ＞ Yunxin301 ＞ Li 53 ＞ Tie hetao ＞ Yunxingaoyuan ＞ Yunxin 306 ＞ Santai ＞ Yangpao ＞ Ziyuan ＞ Wei 2；according to the cold hardiness，Hartely and Chandler had high cold resistance；Yunxin yunlin，Yunxin301，Li 53，Tie hetao，Yunxingaoyuan had medium cold resistance；Yunxin 306， Santai，Yangpao had low cold-tolerance；Ziyuan and Wei2 had no cold resistance.