Studies On Genetic Diversity In Cercis Chinensis

Cercis chinensis was a cultivated ornamental tree species in Caesalpiniaceae family, naturally distributed in temperate zone, including Central China, Northwest, Central South and North of China, mainly surrounding Qinling and Funiushan Mountains, and has a widely cultivated distribution from Liaoning province to Guangdong province. It was usually cut away as shaw in afforestation because its importance was neglected by natives and the resources suffered to destroy seriously. Based on field investigations and analysis of its natural and cultivated distribution, seven natural populations and two cultivated populations with thirty individuals in each population were sampled and examined by using the markers analysis of phenotype and isozyme. The genetic diversity of C. chinensis were evaluated and compared at two levels of phenotype and isozyme by the same experimental materials .The results were obtained as follows:(1) Phenotypic diversities among/within populations were discussed based on 14 traits such as leaf, fruit, seed. The coefficient of variation(CV) was 3.23%to 28.46%.Analysis of variance for all characteristics were significantly different among populations and among individuals within population. The mean phenotypic differentiation coefficient(Vst) shows that the variation among populations (32.3 %) is lower than that within population(67.7%). The coefficient of variation(CV) of the 5 seedling traits were little larger than that of the 14 parent traits, ranging from 6.94% to 18.36%. As the altitude became higher, the leaf and seed became bigger. The shape of legume changed from narrow-column to broad-column, the shape of seed changed from circle to oblong oval, upon increasing of longitude and latitude. There exist correlations among the morphological characters mentioned above. According to the correlation analysis, the populations of Cercis chinensis investigated may be divided into two groups and two sub-groups.(2)A gel electrophoresis method was used to study the genetic diversity. Five of 14 loci from 8 enzymes assayed were polymorphic. Cercis chinensis maintained low level of genetic variation as compared with the other species. At species level, the mean number of alleles per locus (A) was 1.4286, the percentage of polymorphic loci(P) was 35.71 %, and the observed heterozygosity(Ho) was 0.1670.At population level, the estimates were 1.2738(A), 23.81 %(P), and 0.1695(G=Ho), respectively. Genetic differentiation (Gst) was high among populations, Gst was 0.0989, and the means of genetic distance 0.0141.The Nei's genetic identity ranged from 0.9999 to 0.9709.The gene flow was 2.6315. The estimates for cultivated C.chinensis (A=1. 2857, P=21.43%, Ho=0.1553), exist certain difference to contrast with natural C.chinensis. According to the UPGMA cluster analysis based on the genetic distance, 2 natural populations located in western and 2 natural populations in eastern of the geographical distribution are classified into 2 sub-groups in separate, there was no clear relationship between genetic distance and geographic distance among populations. The low level of genetic diversity of C.chinensis might related to the long-term utilizations as economic tree species in history, comparatively serious disturbance and environmental damage by human beings, and secondary forests of the existed stands.(3) By the same sampling, the diversity levels are different among phenotype, isozyme markers. Genetic cluster analysis is similar based on the results of phenotype, isozyme markers. There are still some rough coupling relationship among the results from different kinds of markers, for instance, the diversity order of populations with research on phenotypic and isozyme diversity in Cercis chinensis, the abundance of variation were in South and West of Qinling Mountain.(4) According to the analysis of phenotype and isozyme , it was preliminary to confirm that the populations in south of Qinling and west of Qinling were adaptable to be prioritized for conservation. Moreover, the protection of artificial resources couldn't neglect.In summary, the quantitive criteria for evaluating genetic diversity and sampling stategy for genetic resources conservation and utilization of Cercis chinensis have been discussed, and the results could be used to guide genetic resources collection, conservation and elite breed selection of Redbud. This study was significative for genetic diversity research and conservation of Cercis.