Comprehensive Evaluation Of Different Strawberry Varieties' Cold Tolerance

9 strawberry varieties including'Elsanta','Caomeiwangzi','Dajiangjun', 'Kinuama','Hongruiguang','Maliya','Oubao','Allstar' and 'Xiangfei'were selected to compare their cold tolerance. Their semi-lethal temperatures (LT50) and leaves'physiological and biochemical indexes, such as plasma membrane permeability (PMP), absolute water content (AWC), relative water content (RWC), the content of chlorophyll a and chlorophyll b, water soluble sugar (WSS)content, water soluble protein (WSP) content, free proline (Pro) content, malondiadehyde (MDA) content, superoxide dismutases (SOD) activity and peroxidase (POD) activity were detected or measured as natural temperature falling during late autumn to early winter. And their cold tolerance was evaluated comprehensively using principal component analysis (PCA) and hierarchical cluster analysis (HCA).The result indicated as below:1.After measured, the LT50 of'Allstar'having the strongest cold tolerance was-31.27℃, but that of 'Elsanta' having the weakest cold tolerance was-14.36℃, and others were among of them.2. As temperature falling, the water content and RWC of 9 strawberry varieties decreased. Meanwhile, the water losing had a negative correlation with their cold tolerance. The low temperature destroyed leaves membrane system, which caused PMP and MDA content to rise, Chla+b to decline and Chla/b to rise respectively. WSS, WSP and Pro content risen, which prevented losing water and protected proteins as temperature falling. The low temperature disturbed ROS metabolism balance. Protected enzymes joined eliminating superfluous ROS in a certain extent, but superfluous ROS might go beyond eliminating ability of SOD and POD. Superfluous ROS destroyed membrane and affected activities of SOD and POD, which resulted in the declining of SOD gradually, and the rising of POD at the beginning then declining.3. The final scores got from PCA agreed well with LT50 results. And 9 strawberry varieties were classified into 3 clusters by HCA.'Allstar'and'Xiangfei' had strong cold tolerance,'Elsanta','Maliya'and'Kinuama'had weak cold tolerance, and others were among of them. The results were in accord with the filed observation. Multianalysis methods had important meaning in comprehensive evaluation of plant cold tolerance.