Abstract: Through the determination of cold tolerance physiological indexes of different Chinese bayberry varieties, cold tolerant germplasm were screened to provide theoretical basis for cultivation and production. In this study, 12 main cultivars such as Zijing, Zaoxian, Zaose, Chise, Shuijingzhong, Shenhongzhong, Ruiguang, Zaojia, Muyemei, Dongkui and Zaodamei were selected as the research objects. One-year-old branches were collected and treated at 0 ℃ for 24 h. The contents of soluble sugar (SS), soluble protein, proline, malondialdehyde, POD activity, SOD activity, CAT activity and relatively electrical conductivity were measured. By comparing the differences of 8 physiological indices of 12 bayberry varieties one-year-old branches under cold stress, the cold tolerance of different varieties was evaluated comprehensively based on principal component analysis and cluster analysis. According to principal component analysis, the most important index that affecting cold tolerance of Chinese bayberry was SS. The comprehensive evaluation model was F_n=0.324F₁+0.214F₂+0.178F₃+0.140F₄. The order of cold tolerance of 12 varieties was Biqizhong >Zaoxian>Zijing>Muyemei>Shuijingzhong>Zaodamei>Zaojia>Zaose>Shenhongzhong>Ruiguang>Dongkui>Chise. Among the 12 cultivars, Biqizhong had the strongest cold resistance, and could be planted in the widest range; Zaoxian, Zijing and Muyemei that also had strong cold resistance were worth popularizing in north of Zhejiang Province; Shenhongzhong had a special cold tolerance mechanism, which still needed further study; Chise and Dongkui were affected seriously by low temperature, and therefore they needed cold protection measures.

Key words: Chinese bayberry, branch, cold resistance, physiological index, components analysis