Abstract:

【Objective】 There are abundant Japanese plums (Prunus salicina L.) germplasm resources in China, which are distributed widely in geography. The better understanding of the diversity, the genetic structure and the relationship between sympatric related species, can be helpful to clarify the process of domestication of the cultivated groups of plum and the role of the related species, also further contribute to the in-depth exploration of local resources and enhance the fruit quality in breeding. 【Method】 The 22 pairs of SSR markers covering the entire genome were used to scan 48 samples, including 38 accessions of P. salicina from different sources and 10 accessions of the variation types or related species, by high-throughput fluorescence capillary electrophoresis platform. The polymorphism of 22 SSR loci and genetic diversity of 48 samples were evaluated via the software GenAlEx 6.41, and the dendrogram of these accessions was constructed by using the NTSYS-pc Version 2.1 program. The STRUCTURE 2.2 software based on Bayesian clustering method was used to analyze the genetic mixture of samples and to perform an assignment test on the studied individuals. 【Result】 The detected alleles of 22 SSR primers ranged from 3 to 21, with an average of 13.54 alleles for each locus. A total of 298 alleles were detected in these accessions, 51.8% of which were rare alleles. The values of average effective allele (Ne), average Shannon's diversity index (I), observation heterozygosity (Ho) and expectation heterozygosity (He) indicated that the diversity was the highest in the southern population, followed by the northeast population, which also indicated that the diversity of the Prunus simonii was lower than that of northern China. The analysis of molecular variance (AMOVA) showed that 69% of the diversity in P. salicina was within the population, and only 31% was among populations. On the basis of the data comparisons of the genetic differentiation coefficient and Nei's genetic distance, the results showed that there were extremely significant genetic differentiation and appropriate genes mixture among different geographical populations. The results of cluster analysis implied that the breeding cultivars abroad were closely related to the local accessions in southern China, and the northern cultivars population was similar with P. simonii, the northeast cultivars population had close relationship with Prunus ussuriensis. The genetic structure analysis indicated that the accessions in P. salicina were divided into four types: northern cultivars population, northeast cultivars population, southern cultivars of small fruit and crisp meat population, and southern cultivars of large fruit population (including foreign breeding cultivars). 【Conclusion】 The diversity of the southern varieties were the most abundant in the P. salicina, followed by that of Northeast China varieties, foreign varieties and Northern varieties. In order to enhance the adaptability, the northeast population might be introgressed with P. ussuriensis. P. simonii might be a special type which was highly domesticated from Chinese plum in Northern China, and it had high heterozygosis owing to asexual reproduction by grafting. The large fruit accessions in Jiangsu and Zhejiang regions played an important role in modern breeding varieties abroad.

Key words: Prunus salicina L., genetic diversity, population structure, gene flow