| Cerasus serrulata Lindl., belonging to Cerasus of Rosacae, distributes widely in most areas of China, Japan and Korean Peninsula with continuous and crossed morphological variations which have caused controversy over its taxonomy status. Meanwhile, Cerasus serrulata posses eminent ornamental value along with rich and superior genetic characters which has great value for developing new flowering cherry cultivars. Howerer, the great resource is overlooked. Based on this, 8 C. serrulata populations with totally 224 individuals were collected to study the genetic diversity and genetic structure by 17 SSR markers. The study could provide theoretical and practical reference to further development and utilization of C. serrulata resources, and also could provide molecular evidences for variation and differentiation between C. Serrulata populations. The main results were as follows:1. Species level of genetic diversity of C. serrulata: A total of 113 alleles of 17 SSR loci were detected from 224 individuals of 8 populations. The average and effective allele number(Ne) of each loci were 6.647 and 2.471. Average observed heterozygosity(Ho), expected heterozygosity(He), Nei's genetic diversity index(H), Shannon diversity index(I) were respectively 0.249, 0.488, 0.634, 0.939, showing a polymorphism of the SSR loci and high genetic diversity on species level of C. serrulata. Wide distribution, cross pollination, birds and people activities which promoted gene flow might have made contributions. Almost every loci significantly deviated from Hardy-Weinberg equilibrium, indicating that C. serrulata lacked heterozygous and was not panmixis.2. Population level of genetic diversity of C. serrulata: Percentage of polymorphic loci(PPL), average observed heterozygosity, expected heterozygosity, Nei's genetic diversity index, Shannon diversity index were respectively 92.65%, 0.249, 0.488, 0.498, 0.939, showing a high genetic diversity on population level of C. serrulata, while lower than on the species level. Relatively weaker competitiveness, habitat destruction, geographical barrier such as high mountain, rivers and ocean which hampered gene flow might have depressed population level genetic diversity. According to Nei's genetic diversity index and Shannon diversity index, 8 C. serrulata populations were ranked by genetic diversity from high to low as: Fengcheng of Liaoning Province(FHS), Lin'an of Zhejiang Province(TMS), Qingdao of Shangdong Province(LaoS), Seoul of Korea(K-NS), Huangshan of Anhui Province(HS), Lianyungang of Jiangsu Province(YTS), Jiujiang of Jiangxi Province(LS), Wuyishan of Fujian Province(HGS).3. Genetic differentiation between C. serrulata populations: The gene flow(Nm) was 0.8548, indicating a low gene flow among C. serrulata populations. Molecular genetic variance analysis(AMOVA)(FST=0.221) revealed that 22% genetic variation occurred among populations, which meant a significant genetic differentiation between C. serrulata populations. Lack of gene flow and specialized habitat could be the reason.4. Mantel test showed no significant correlation between genetic distance and geographic distance of C. serrulata populations( r=- 0.13062,p=0.2632).5. Analysis of UPGMA based on Nei's genetic distance clustered the 8 C. serrulata populations into 3 groups: 1. Seoul, Fengcheng, Qingdao, Lianyungang and Huangshan; 2. Jiujiang and Lin'an; 3. Wuyishan. The clustering result basically accorded to the geographic distribution from north to south, except Huangshan.6. STRUCTURE showed that the 8 C. serrulata populations originated from 3 different gene pools: 1. Fengcheng, half individuals of Qingdao, half individuals of Huangshan and Wuyishan were from one gene pool; 2. The other half individuals of Qingdao and Huangshan, Seoul and Lianyungang were from one gene pool; 3. Jiujiang and Lin'an were from anther gene pool. At the situation of K=4, population of Seoul was separated up alone to a different gene pool while almost no changes occoured in other groups. Result of principal component analysis(PCoA) corresponded to the situation when K=4 of STRUCTURE analysis. Results of STRUCTURE analysis and PCoA explained the special clustering status of Huangshan population in UPGMA tree.7. Population of Lianyungang which was mainly consisted of Cerasus serrulata var. pubescens showed no specificity in any analysis, indicated no obvious difference between C. serrulata var. pubescens and C. serrulata var. serrulata, and indumentum characteristics existed widely in C. serrulata.It is suggested that protection should take place in parallel with exploitation and utilization of C. serrulat resources. Populations of Fengcheng in Liaoning Province and Huangshan in Anhui Province can be the focus for their rich genetic resources, while populations of Wuyishan in Fujian Province should be taken importance to protect. Germplasm banks of C. serrulata are ought to be established, and at the same time work of cultivating new superior cultivators is supposed to be carried out. |
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