Phylogeography Of Prunus Subgenus Cerasus And Genetic Diversity Of P.pseudocerasus

Prunus subgenus Cerasus belongs to the family Rosaceae,distributing wide in the temperate zone of Northern Hemisphere,mainly in West China,Southwest China, Japan and Korea.There are about one hundred species in Prunus subgenus Cerasus. They have been destroyed by disaster and anthropogenic activities.The genetic diversity and differentiation in Chinese sour cherry Prunus pseudocerasus Lind1.and the phylogeography of Prunus subgenus Cerasus has been studied in this paper, which will play an essential role in the use of these germplasm resources.The patterns of genetic diversity of P.pseudocerasus were analysed using ISSR marker,and based on the present study,conservation strategies were proposed to preserve this valuable natural germplasm resource.The haplotype of Prunus subgenus Cerasus were analysed to infer phylogeography using cpSSR marker and the the possible refugia was suggested.This study focuses on two subjects:1.The phylogeographic study on Prunus subgenus CerasusIn this study,the phylogeography of 228 Prunus subgenus Cerasus individuals, which corresponded to 47 populations,were investigated using cpSSR markers. Totally,thirteen selected primer pairs generated 2 to 5 alleles,combining in 30 different haplotypes.Most of the haplotypes were shared only by the geographicaliy adjacent populations that belonged to the same species except 5,8,18 and 22,which distributed in a relatively wide range.The results of nested clade analysis showed that 30 haplotypes constituted 5 steps.According to the results,the reason of their geographical distribution were inferred.Clade 2-1 was caused by long-distance colonisation and/or past fragmenation(not necessarily mutually exclusive),and clade 3-4 and clade 4-1 were caused by contiguous range expansion.The geographical distribution of haplotype was probably linked with the migration of Prunus subgenus Cerasus before Quaternary glaciation.The direction was from Southwest China to mountains in Central China,and some of them moved on to East China,in line with that found in the eastern Asiatic region.In the present study,the results implied that Yunnan Province,Sichuan Basin,Wulingshan Region,Qinling-Daba Mountains and Yangtze-Huaihe Region might be the refugia of Prunus subgenus Cerasus during Quaternary glaciation.We postulated that the expansion of Prunus subgenus Cerasus from refugia formed its pattern of modern distribution.The populations in Yangtze-Huaihe Region expanded northwardly to Shandong Province,while populations in Sichuan Basin expanded eastwardly along Qinling Mountains and Taihang Mountain to Northeast China,such as North of China and Liaoning Province.2.The genetic diversity and structure of P.pseudocerasus and its conservationIn this study,the genetic diversity and differentiation of ten natural P. pseudocerasus populations were investigated using inter-simple sequence repeat (ISSR) markers.Totally,eighteen selected primers generated 150 loci,with an average of 8.33 bands per primer.The results showed that the percentage of polymorphic bands(PPB) was pretty low at the population level(PPB = 1.13-32%), but relatively high at the species level(PPB = 84%).Besides,a high level of genetic differentiation among populations was detected based on the gene differentiation coefficient(G_ST = 0.7118) and the hierarchical analysis of molecular variance (AMOVA)(φ_ST = 64.53%,P＜0.001),in line with the low inter-population gene flow (N_m = 0.2025).Moreover,Mantel test revealed a significant correlation between genetic and geographic distances among the populations(r = 0.5272,P＜0.005).The high level of intraspecific genetic diversity was probably related with its life history traits,while its small population size and the resultant high levels of genetic drift and inbreeding might explain the low genetic diversity within populations.The relatively high inter-population genetic differentiation was largely attributed to its small population size,habitat fragmentation,the mode of pollen and seed dispersal,and geographic isolation.Based on the present study,conservation strategies were proposed to preserve this valuable natural germplasm resource.According to our field survey,we suggest the emphasis for in situ conservation be placed on populations with high genetic diversity,such as Population YJ,CK,YN, XX and FP.Besides,ex situ conservation should be a good complement to the in situ measures.Translocations are becoming increasingly popular since they are effective in both removing detrimental variation associated with inbreeding depression as well as restoring neutral genetic variation to historical levels.