| Chinese cherry (Cerasus pseudocerasus Lindl.) is a deciduous fruit tree originating in China. It belongs to Rosaceae, subfamily Prunoideae, genera Cerasus. It has a cultivation history of about 3,000 years. Its prematurity and ornamental values make it be of high economic value. Chinese cherry has a broad distribution in China. There are rich wild cherry resources in Sichuan, Yunnan, Shanxi, Guizhou province. And provinces like Henan, Anhui, Sichuan, Guizhou, Gansu and Chongqing are dotted with important cultivated germplasm of Chinese Cherry. At present, there is no comprehensive and deep understanding of genetic background of wild and cultivated recourses of Chinese cherry, which influences the protection and utilization of the excellent germplasm. In view of the above, in this study we collected 263 Chinese cherry samples from Sichuan, Anhui, Henan, Shaanxi, Guizhou, Chongqing and other cities, including eight Chinese cherry cultivation populations and nine Chinese cherry wild populations. Based on cpDNA sequence rp116 intron, this article mainly discusses genetic diversity and genetic structure of Chinese cherry population. The results are as following:1. Evaluation of genetic diversity of Chinese cherry resources. The result of genetic diversity of chloroplast fragment sequences from 263 samples shows 1) 14 polymorphic sites are detected in 263 rpll6 intron sequences and 22 chloroplast haplotypes are detected in all the 17 populations. Haplotype diversity (Ha) distributes in the range of 0.000-0.879, and the haplotype diversity (Hd) of the total population is 0.689. Nucleotide diversity (π) ranges from 0.00000 to 0.00316, and the nucleotide diversity (n) of the total population is 0.00184.2) Genetic diversity is greatly different between different populations, in which wild population has high level genetic diversity, whose average haplotype diversity (Hd) is 0.776, and average nucleotide diversity (π) is 0.00258. While the average haplotype diversity (Hd) of cultivation population is 0.575 while average nucleotide diversity (π) is 0.00076. So it can be inferred that Chinese cherry has rich genetic diversity, which is consistent with most research results. The reason for lower level genetic diversity of cultivation population may be the dramatic decrease of effective population caused by the bottleneck effect resulting from long-term domesticated cultivation and asexual reproduction.2. Population genetic structure of Chinese cherry. Results of population genetic structure show:1) results of pairwise genetic differentiation among populations show that pairwise genetic differentiation coefficient of 17 Chinese cherry populations Fs, ranges from 0.0000 to 0.8912. Fst is not significant except that of YS GY, YS QC, YS SN and all cultivated populations, so pairwise genetic differentiation is not obvious. Fst of all cultivated populations and all wild populations is 0.1558, (P=0.0000). Although Fst among several wild populations are obvious, Fs, is not obvious in general.2) AMOVA analysis reveals that heritable variation of the total populations and cultivation populations mainly exists within populations, while 65.57% heritable variation of cultivation populations are among populations,34.43% within cultivation populations.3) The genetic distance based on K-2P model shows the genetic distance between every two of the 17 populations ranges from 0.000 to 0.004 and the genetic distance of wild Shangnan population and other populations is the most distant. In the clustering analysis based on genetic distance of K-2P model, the 17 Chinese cherry populations can mainly be divided into two branches. Qingchuan wild population and wild Shangnan population are clustered into one (II), the other populations are clustered into the other (I). This indicates that Qingchuan wild population is genetically distant from wild Shangnan population and the rest populations, molecular NJ clustering and haplotype network diagram is a reflection of the topology structure, indicating that:the 22 haplotypes are divided into two major branches A and B and A and B branches include 13 and 9 haplotypes. Branch A is divided into A1 and A2 and B sub branches B1 and B2. Haplotypes of Hapl and Hap2 are two haplotypes that are most widely distributed, and they have high frequency.4) Tests of neutrality and mismatch distribution analysis results show that:Tajiama’s D value of the cultivation populations is significantly negative, and its mismatch distribution curve is a peak curve, indicating that the cultivation population is not a stable population and deviates from the neutral evolution, recently experiencing massive population expansion. From the above results, it can be deducted that the genetic differentiation of Chinese cherry populations is smaller, Chinese cherry shows no significant population genetic structure. The reason for that may be the breeding system and seed dispersal mechanism of Chinese cherry. |
PDF Full Text Request