Selection Of Superior Varieties For Extension And Analysis Of Genetic Diversity In Pomegranate Cultivars

The genetic diversity analysis and cluster analysis were performed in 73 varieties of 15 types of pomegranate from 2005 to 2007, using 9 branch-leaf traits, 9 fruit quality traits, resistance to fruit cracking, resistance to dry rot as morphological markers, and 216 AFLP molecular markers. Fruit quality traits and resistance to fruit cracking, resistance to dry rot traits in pomegranate resources were used to comprehensively evaluate and to screen the superior cultivars for extension.The variance analysis of resistance to fruit cracking showed that the variance was significant among cultivars. To select the cultivars with highly resistance to fruit cracking was one of the efficient ways to decrease the fruit cracking seriously arising in the production. Among the 60 cultivars, the cultivars of immunity (CI = 0), of high resistance (CI = 0.1-5.0), of resistance (CI = 5.1-25.0), of susceptibility (CI = 25.1-50.0), and of high susceptibility (CI = 50.1-100.0) to fruit cracking, were 2 (0.03%), 13 (21.67%), 41 (68.33%), 3 (6.7%) and1 (1.67%), respectively.The variance analysis of resistance to dry rot showed that the variance was also significant among cultivars. Among them, the cultivars of immunity (CI = 0), of high resistance (CI = 0.1-5.0), of resistance (CI = 5.1-25.0), of susceptibility (CI = 25.1-50.0), and of high susceptibility (CI = 50.1-100.0) to dry rot, were 4 (5.49%), 29 (39.74%), 37 (50.69%) and 3 (4.11%), respectively.The analysis of correlation coefficient (r) of resistance between the fruit cracking and the dry rot in pomegranates showed that the r-value of all cultivars was insignificant, but the r-value of the cultivars in two types of'Sanbaitian'and'Tianhongdan'was significant or extremely significant, which indicates that resistance to two disease is complex.The analysis of 28 correlation coefficients (r) between 8 fruit quality traits showed that the 12 r-values (41.86%), between the traits of the fruit shape indexes (the ratio of vertical diameter to transverse diameter), the fruit skin thickness, the weights of 100 seeds, the soluble solid contents, Vc contents, total acidic acid contents in seed skin, and the hardness of the seed, were significant or extremely significant. Therefore, it is practicable to select the cultivars with the multiple superior traits for extension as the high fruit shape index, thin pericarp, the high contents of soluble solid and Vc, the low total acid contents, and the soft seeds.Principal components analysis (PCA) of 8 fruit quality traits in the 67 cultivars of 12 types showed that the five principal components were proposed for the superior variety selection in pomegranates, which contains 82.38% information of the eight traits. Therefore, these five principal components may be more accurate than the weighed scores from a few traits for the selection and breeding because PCA can minimize the effects of the correlation coefficients between the traits on the selection.After a comprehensive evaluation of 8 fruit traits, resistance to fruit cracking and to dry rot,'Linyan-23'of the type'Jingpitian', and'Linyan-29'and'Linyan-38'of the type'Dahongsuan', exhibiting high fruit quality and high resistance, were suggested for extension in the pomegranate production.Diversity analysis using morphological traits as traits in leaves, branches, and fruits showed they presented highly polymorphism in pomegranate cultivars. Molecular diversity analysis showed that 54.28% AFLP loci exhibited high polymorphism.The grouping results of the cluster analysis using morphological traits in branches, leaves, and fruits, were inconsistent with those of the classification for the cultivar types used in the production. The clustering results using molecular markers were also much different as those using morphological traits. The cluster analysis using AFLP markers provided a theoretic base and a guide for the parent choosing and mating in the pomegranate breeding.