Assessment Of Genetic Diversity And Populations Genetic Structure In Wild Chinese Cherry From Sichuan Province Using SSR Markers

Chinese cherry (Cerasus pseudocerasus Lindl.), the major cultivated specie of worldwide cherry cultivation, is originated from China and wide distributed in China, especially in southwest China, which possesses abundant wild Chinese cherry. The wild Chinese cherry, which exhibits diversiform in characterization and centralized distributions, is considered to be a valuable gene pool for cherry genetic improvement and thus plays a critical role in cherry breeding in the future. However, due to the few population genetics research, deficient specialized collection and evaluation of wild resource and the limitation of research methods, the rich degree, population structure and existence actuality of wild Chinese cherry have not been proved yet. As an important distribution area of wild Chinese cherry, Sichuan has been seldom investigated of its wild cherry resource, the present situation of wild cherry and the genetic level are still unknown in this area. Based on the present situation, we investigated the genetic diversity and differentiation of five wild Chinese cherry populations of Sichuan by13SSR markers. Also we discussed how the internal and external factors were acting on genetic diversity and genetic structure of wild Chinese cherry in Sichuan. The main results as follows.Genetic diversity of wild C. pseudocerasus populations in Sichuan were studied based on13microsatellite loci. For a total of133individuals of5populations collected from5regions, a moderate high level of genetic diversity was observed with the number of alleles per locus (Na) ranging from5to10(average7.54) and relatively high gene diversity (H) value0.6692. At population levels, gene diversity (H) varied from0.5922-0.6450with the mean of0.6146and Shannon diversity (I) from1.1330to1.2993with the mean of1.2150, which shows high level of genetic diversity. The level of genetic diversity for TL population are the highest (H=0.6450) and YZ population are the lowest (H=0.5922). All of the five populations possessed rare alleles which appeared most in TL (17) and three unique alleles were found in GX. We think that the long age of Chinese cherry populations and the distributing area, which close to diversity region, were the main reason for the high level of genetic diversity in this research.The AMOVA analysis revealed low genetic differentiation among populations, with only6.67%of total variability partitioned among populations (P<0.001). This consisted with close genetic distance (GD<0.2408), high genetic identity (GI>0.7845), low genetic differentiation (Fst=0.0831) and strong gene flow (Nm=2.7327).The high Fis at specie and population level (0.3989and0.4208) shows significant inbreeding (P<0.001). Five populations deviated from Hardy-Weinberg Equilibrium all most loci except EMPA022, and the observed heterozygosity was significantly low than expected heterozygosity. Rivers and birds helped the gene exchange between populations in long distance. The self-pollen of Chinese cherry with high genetic diversity can be proof of the long age of these populations.