Studies On Genetic Diversity And Mating System Of Elaeagnus Mollis Diels

Elaeagnus mollis Diels belonging to Elaeagnus of Elaeagnaceae,is a rare,endemic and endangered plant in China.This plant mainly distributes in YiCheng,XiangNing,SanMen Town of PingLu,HeJin,JiShan,JiangXian,XinJiang,PuXian and Liu Lin,ect.of Shanxi Province.In addition,the areas LaoYu and GanYu in Shaanxi Province also have a small amount of distribution.In this paper,the genetic diversity,genetic structure,population dynamic variation and the mating system of the wild population for E.mollis were studied by microsatellite(SSR)molecular markers and chloroplast sequence fragments for evaluating the current situation for genetic diversity of population,revealing endangerment mechanism and providing foundational information for conservation,development and utilization of germplasm resources.Seven natural populations of E.mollis from YiCheng,XiangNIng,PingLu in Shanxi province and HuXian in Shannxi province are collected to be researched and the main conclusions are as follows:(1)Seventeen pairs polymorphic,specific SSR molecular markers for E.mollis were developed using the magnetic beads enrichment method,and the polymorphism of these markers were detected in two populations of E.mollis from Yicheng County,Shanxi Province.The results showed that the number of alleles(Na)at each locus of this set of SSR markers was 1-9(mean 3.75);the observed heterozygosity(HO)was 0-1.000(mean 0.533),the expected heterozygosity(HE)was 0-0.826(mean 0.522),and the polymorphic locus ratio was 97.06%.It is shown that this SSR marker has high resolution and could be used for the study of genetic diversity,population genetic structure and the mating system of E.mollis.(2)SSR analysis showed that at the population level(Na=4.13,Ne=2.450,I=0.981,HO=0.536,P=97.48%)and species level(Na=7.82,Ne=3.188,I=1.298,HO=0.532,P=100%),E.mollis both had a high genetic diversity level.Bottleneck analysis showed that the population of E.mollis in Huxian area of Shaanxi Province could have the bottleneck effect.AMOVA showed that the genetic variation was mainly in the population(81.44%),but the FST value was 0.15484(P <0.001),which indicated that there were significant genetic differentiation among the populations.Structure analysis showed that the populations of E.mollis in Shanxi and Shaanxi had significant differentiation,and the gene flow Nm<1 showed that the exchange of the populations of these two regions was at the low level.Mantel's analysis also showed that between the two populations of E.mollis in Shaanxi and Shanxi had severe genetic differentiation.Geographic segregation may be a major cause of genetic differentiation.(3)Based on six chloroplast gene fragments,the haplotypes of seven populations of E.mollis were analyzed by Network.The results showed that there were 4 haplotypes in the seven populations.However,only the haplotype type of the population in SanMen town,Ping Lu county,Shanxi Province is more abundant,but there is only one type in the populations of other regions.The relationship between the history and geographical distribution of haplotypes of all populations of E.mollis was tested,the results showed that after the formation of the haplotypes in Shanxi Province,they may have experienced a geographical redistribution,while the haplotypes between Shanxi and Shaanxi may not have experienced a geographical redistribution.The BEAST software was used to estimate the relative differentiation time of the four types of haplotypes.The results showed that the haplotype differentiation time of the population in Huxian county of Shaanxi Province was earlier than that in other areas.However,in Shanxi Province,the haplotype differentiation time of one of the three haplotypes in Pinglu county is relatively earlier,indicating that this place may be the glacial refugia of E.mollis in Shanxi Province.(4)The niche simulation showed that at the last interglacial period,the last glacial period,the mid-Holocene and the current,the core distribution area predicted(probability P>90%)was mainly distributed in the southern part of Shanxi Luliang Mountains,Shanxi Zhongtiao Mountains,and along the northern slope of Shaanxi Qinling Mountains as well as the “Beishan” Mountains at the junction of northern Shaanxi and Guanzhong areas(mainly constituted by Qiaoshan,Huanglongshan,Ziwuling and Longshan mountains),which may be caused by the narrow area of the current distribution for the wild populations,or may be caused by the geographical barrier that E.mollis would not easily expand its distribution.(5)Based on the SSR dates,the results of mating system stuides showing that E.mollis had a high multiple loci outcrossing rate not only at the population level(tm=0.990),but also the species level(tm=0.957),indicating that this species was mainly outcrossing.The low level of the biparental inbreeding of the two populations showed that the inbreeding of E.mollis was at the very low level,and the most offsprings were produced by outcrossing.Moreover,the inbreeding level was lower than the result of artificial pollination,which may be caused by the reason that many fruits fell off during the develoment process bacause of its own physiological reproductive characteristics or external environmental condition such as light,temperature,precipitation and so on.