| As one of the worldwide cherry species, Chinese cherry(Cerasus pseudocerasus (Lindl.) G. Don)is native to China and has been cultivated more than 3000 years. It inhabits wide eco-geographic regions in China. Currently. Chinese cherry landraces are widely distributed among Sichuan Basin. Yunnan-Guizhou Plateau, QinLing Mountains, North China Plain and partial East China Plain, and wild resources are mainly distributed among Sichuan Basin. Yunnan-Guizhou Plateau and partial QinLing Mountains. With beautiful flowers, attractive smell and rich colors of fruits, it exhibits abundant phenotypic diversity both among and within populations, and has relatively high ornamental value and commercial value. In the recent years, many cherry resources have been lostdue to habitat destruction, replacement of other fruits and extensive management. The latest researches of Chinese cherry mainly have been conducted in partial regions or only on single type (landraces or wilds), which could not comprehensively reveal the current situation of cherry resources of China. In this study,17 SSRs developed from the C. pseudocerasus genome were used to estimate the genetic diversity and population structure of 542 individuals (338 landraces and 204 wild ones) from 60 counties of 11 provinces of China.1. The selection and assessment of SSRs developed from the C. pseudocerasus genome.The selected SSR loci in our study exhibited relatively high polymorphism, specificity, amplification rate and excellent repeatability (An=0.137,I=0.808,PIC=0.367).7 out of 17 loci were evenly distributed across the six out of eight chromosomes of the relative, Cerasus avium.17 SSR loci contained all repeat motifs, mainly including the dinucleotide repeats (64.71%) and trinucleotide repeats (27.27%). Above all, these markers can be effectively used to examine the genetic diversity of C. pseudocerasus.2. The analysis of genetic diversity of Chinese cherryIn this study, we used 17 efficient SSRs to assess the genetic diversity of 338 Chinese cherry landraces and 204 wild cherry individuals according to their types and geographic distributions, respectively. The results showed that the genetic diversity of cherry landraces (Na=5.294, Ne=1.645, Ar=3.940, He=0.332,I=0.641) was lower than the wild ones (Na=5.824,Ne=2.120, Ar=5.240, He=00490,I=0.986). Based on different geographic distributions, the genetic analysis suggested that the two highest levels of genetic diversity were observed in LYG (He=0.355,I=0.672) and LQL (He=0.355,I=0.649), followed by LHBD (He=0.241,I=0.483) and LSC (He=0.241, I=0.483). And that of wild group was as following order as WSC (He=0.491,I=0.986), WQL (He=0.429,I=0.793) and WYG (He=0.411,I=0.764).3. The analysis of population structure and differentiationThe results of STRUCTURE, NJ tree and PCoA indicated that Chinese cherry landraces and wild ones could be roughly divided into two groups and there was frequent gene introgression between them in their overlapping regions. Furthermore, the cherry landraces could be clustered into two subgroups, subgroup ? (LSC and LYG) and subgroup ? (LQL and LHBD), showing a clear correlation to geographic distribution. The wilds showed a obvious mixture and crosses, and had no clear structure. Moreover, we detected a relatively high differentiation within LQL and inferred it may be the transition zone between LSC and LHBD.According to the results of AMOVA, the genetic variation mainly occurred within groups. Overall, there was moderate differentiation within Chinese cherry (FST=0.098, Nm=2.298). Moderate differentiation was detected between wild and landraces group (FST=0.095,Nm=2.382). Moreover, the differentiation was relatively high within landraces (FST=0.131, Nm=1.655), yet it was slight within wilds (FST=0.041, Nm=5.771), indicating that the frequent gene flow and numerous shared ancestral polymorphisms might retard the tempo of differentiation within wild group. |
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