Comprehensive evaluation on heat tolerance of various Chinese cabbage seedlings

At high temperature in a chamber under artificially controlled conditions,5 inbred lines and 4 F1 hybrids of Chinese cabbages at their seedling stage were studied for their heat tolerance. The factor analysis,subordinate function and cluster analysis were applied to evaluate the tested accessions based on the physiological and biochemical indices. The result obtained from the factor analysis indicated that the 8 indices could be characterized as 3 prinipal components,which gave an accumulative contribution rate up to 0.921. A comprehensive evaluation on the heat tolerance was performed based on the D value of subordinate function analysis. The cluster analysis classified the 9 accessions into 3 categories:(1) the highest heat tolerance accessions that included Xiaxiu-1,Xiafu-2 and Xiayou-1,(2) the intermediate accessions that included Zaoshu-5,Bai-yang,Zao5-1 and Zaoza-5,and (3) the sensitive-to-heat-stress accessions that included 020w-8 and Deyang.