Analysis Of Genetic Structure Of Cryptomeria Populations In East Asia

The Cryptomeria plants are evergreen tree of Taxodiaceae.The taxonomic status of Cryptomeria japonica var.sinensis and Cryptomeria japonica var.japonica is still cont:roversial.For one view is that Cryptomeria japonica var.sinensis and Cryptomeria japonica var.japonica are two independent species,and another view is that they are different varieties of the same species.At present,foreign experts and scholars have done a lot of research on Cryptomeria japonica var,japonica,but little molecular research have been done on Cryptomeria japonica var.sinensis.The level of genetic diversity and genetic structure of Cryptomeria japonica var.sinensis level are still unclear,and their genetic relationship and population genetic structure differences with Cryptomeria japonica var.japonica are not clear.Therefore,EST-SSR markers were used to study 21 Cryptomeria。populations in East Asia to analyze the genetic diversity of Cryptomeria and its population genetic structure,understand the population dynamic history,and explore the origin and evolution of Cryptomeria.Relevant research work can provide scientific basis for the protection and breeding of Cryptomeria.The results are as follows:(1)Population genetic diversity of Cryptomeria20 EST-SSR primers were used to analyze the genetic diversity of 21 Cryptomeria populations in China and Japan.The results showed that the overall population had a moderate level of genetic diversity;,and the genetic diversity of Chinese populations was higher than that of the Japanese populations.The differences between Japanese populations are small while Chinese populations are large.The Chinese populations which had the highest and lowest genetic diversity among all populations are Lushan(LS)and Tianbaoyan(TB)population.For all populations,the number of alleles(Na)was 4.264;the effective allele(Ne)was 2.494;the Shannon’s information index(1)was 0.919;the observed heterozygosity(Ho)was 0.489;and the expected heterozsity(He)was 0.477.The mean inbreeding coefficient(Fis)was-0.025,the percentage of polymorphic loci(PPB)was 94.30%,the allele richness(AR)was 3.177,and the private allele richness(PA)was 0.169.For the Chinese populations,the number of alleles(Na)was 4.365;the effective allele(Ne)was 2.626;the Shannon’s information index(I)was 0.963;the observed heterozygosity(Ho)was 0.509;the expected heterozygosity(He)was 0.507.The inbreeding coefficient(Fis)was-0.004;the percentage of polymorphic loci(PPB)was 93.50%;the allele richness(AR)was 3.169;the private allele richness(PA)was 0.185.For the Japanese populations,the number of alleles(Na)was 4.173;the effective allele(Ne)was 2.382;the Shannon’s information index(I)was 0.879;the observed heterozygosity(Ho)was 0.471;and the expected heterozygosity(He)was 0.449.The inbreeding coefficient(Fis)was-0.049;the percentage of polymorphic loci(PPB)was 95.00%;the allele richness(AR)was 3.185;the private allele richness(PA)was 0.154.(2)Population genetic structure of CryptomeriaThe results of population genetic structure showed that there was moderate genetic differentiation among populations.The genetic differentiation coefficients of all populations were Fst=0.138,Gst=0.107,and the genetic differentiation between Japanese populations was 0.033,which was significantly lower than the overall average and Cryptomeria japonica var.sinensis groups level(Fst = 0.105).The molecular variance analysis(AMOVA)based on the two groups(Chinese and Japanese populations)showed that the genetic variation within populations was 85.11%,the genetic variation among the groups was 7.94%,and the genetic variation among populations was the lowest at 6.95%.This indicates that the genetic variation of Cryptomeria is mainly within the populations.The gene flow of all populations was 2.065>1,indicating that gene flow is not the dominant factor in genetic differentiation within the populations.Mantel test showed that the genetic differentiation of Cryptomeria populations was significantly correlated with geographical distance(r=0.411 p=0.001).Phylogenetic tree of Cryptomeria based on NJ method showed that 21 Cryptomeria populations were divided into three main clusters,namely,nine populations in China(WT、XTM、TT、PNSL、FZ、YB、TBY、YTG、WYS),eleven Japanese populations(AJG、NBT、DND、BJD、ASH、OKI、AZJ、YKU、ONN、SNG、ISN)(JPN)and Chinese Lushan population(LS).The results is consistent with the principal coordinate analysis(PCA).STRUCTURE analysis showed that 21 populations were divided into three clusters,namely,Nl is 9 Chinese populations except LS(CHN),N2 is 11 Japanese populations(JPN)and N3 is Lushan population(LS),are more reasonable.It is more scientific and reasonable to take Cryptomeria japonica var.sinensis and Cryptomeria japonica var.japonica as different varieties.The results of STRUCTURE analysis of 10 populations in China show that K=3 is the most reasonable.At this time,the LS populations is a single group;PNSL and WT are one;the remaining 7 populations are one.The results of STRUCTURE analysis of 11 populations in Japan showed that K=2 was the most reasonable.At this time,AJG,NBT,DND,BJD,ONN and SNG were homologous groups,and the other 5 groups ASH,OKI,AZJ,YKU and ISN were homologous groups.Bottleneck effect test showed that under TPM and SMM models,seven populations in Japan(63.64%)may have experienced bottleneck effect,while two populations in China(20.00%).(3)Evolutionary history of CryptomeriaConsidering Chinese and Japanese populations as two gene pools,evolution history results showed that the posterior probability of simultaneous differentiation of the two gene pools is the highest.This means that Cryptomeria japonica var.sinensis and Cryptomeria japonica var.japonica were separated from an unknown population NA at the same time between 62100 and 124200 years ago.