Genetic Diversity Analysis Of Disanthus Cercidifolius Var.Longipes

Disanthus including one species and one variety,is a small eastern Asian genus of the family Hamamelidaceae.D.cercidifolius,which occurs in Japan and D.cercidifolius var.longipes,which only occurs in south China.D.cercidifolius var.longipes was listed in the Red List of Endangered Plant Species and Second Grade of the List of Wild Plants Under State Protection in China.This species is significant for the study of phylogeny and floristic geography in east Asia.In order to predicting the potential distribution areas of this genus in different periods which would be helpful to improve our understanding of how the genus responds to climate change and the restriction mechanisms of environmental variables on the potential distribution of the species,we carried out several research.To parsing the genetic information of D.cercidifolius var.longipes,We performed transcriptome sequencing of samples D.cercidifolius var.Longipes using Illumina HiSeq4000 to develope polymorphism SSR loci which were used for the genetic diversity,the degree of differentiation within and between populations,and the genetic structure.The aim is to provide a theoretical basis for the collection,preservation and genetic breeding of germplasm resources of D.cercidifolius var.Longipes.The main findings are as follows:?1?Potential distribution modeling of Disanthus Maxim.In this paper,nineteen populations of Disanthus Maxim.were selected to study the potential distribution of this genus during current,Last Glacial Maximum,and future periods,for which the representative concentration pathways of greenhouse gases were 2.6,4.5,6.0,and 8.5,respectively.A high area under the receiver operating characteristic curve?AUC=0.9999±0.0001?indicated that the prediction accuracy of the MaxEnt model was very high.The precipitation of the wettest month and precipitation of the driest month were the dominant factors affecting the distribution of this genus.Quantitative analysis performed in ArcToolbox were used to compare the distribution dynamic of the genus.An analysis based on the habitat stability of the population(N_stab),the area ratio of the distribution area between Current and other periods?N_a?,and the degree of expansion or contraction?N_e?showed that Disanthus Maxim.underwent contraction coupled with evolution.The suitable distribution area of Disanthus Maxim.will likely alter depending on increases in greenhouse gas emissions in the future.The potential contractions in the distribution of Disanthus Maxim.range from thirty to sixty five percent.It is likely that the Disanthus Maxim.population found in the Wuyishan Mountains would be lost under RCP 8.5,in particular.?2?Development of SSR molecular markers for D.cercidifolius var.longipesWe performed transcriptome sequencing of samples D.cercidifolius var.longipes using Illumina HiSeq4000.After assembling of transcriptome sequences,a total of 32325 uni-genes were obtained.There were 13779 SSR loci identified using MISA,and the occurrence frequency of SSR loci was 42.63%.The distribution frequency of SSR was 1/2.95kb.The di-nucleotide repeat motif was the most abundant among different repeat motifs,accounting for 44.10%of the total number of repeat motifs.Mono-nucleotide and tri-nucleotide repeat motifs accounted for 37.90%and 16.71%,respectively.The AG/CT was the most abundant di-nucleotide repeat motifs,while the AAG/CTT was the most abundant tri-nucleotide repeat motif,followed by ATC/ATG,ACC/GGT,and AGC/CTG.60 pairs of random-selected primers were used to test its availability in the random sample of 8 unrelated individuals from different populations using agarose electrophoresis.46 pairs primers amplified with clear target bands,while 30 pairs were found to be polymorphic using TP-M13-SSR technology.The amplifying rate and proportion of polymorphic loci were 76.67%and 65.22%,respectively.The results showed that the polymorphism of SSR loci developed based on the transcriptome sequences is higher.?3?The genetic diversity and genetic structure of D.cercidifolius var.longipes15 SSR primers were used to analyze the genetic diversity of 261 samples from 12 natural populations of D.cercidifolius var.longipes.The results showed that 129 alleles were detected at the species level.At the species level,the number of alleles?N_a?at each loci ranged from 4 to 15,with an average of 8.6.The effective allele number?N_e?ranged from 1.9987?6.7871,with an average of 3.4669.Shannon information index?I?ranged from 0.8376?2.0412,with an average of 1.3839.The observed heterozygosity?H_o?ranged from 0.1106?0.6245,with an average of 0.3655.The expected heterozygosity?H_e?ranged from 0,5007?0.8546,with an average of 0.6706.The N_ei's gene diversity index?H?ranged from 0.4997?0.8527,with an average of 0.6691.At the population level,the number of alleles?N_a?of ranged from 2.6667?4.2000,with an average of 3.3778.The effective allele number?N_e?ranged from 1.7380?2.4969,with an average of 2.0810.The Shannon information index?I?ranged from 0.6027?0.9474,with an average of 0.7684.The observed heterozygosity?H_o?was 0.2386?0.4675,with an average of 0.3533.The expected heterozygosity?H_e?ranged from 0.3670?0.5206,with an average of 0.4332.The N_ei's gene diversity index?H?ranged from 0.3593?0.5086,with an average of 0.4215.The results of molecular variance analysis?AMOVA?showed that the geneticdifferentiation between the species was obvious.The genetic distance between 12 populations of was significantly different,which ranging from 0.2102 to 1.2794.The genetic distance between the population of Mangshan?MS?and lianzhou?LZ?was the smallest,and the genetic distance between the population of Mangshan?MS?and Longquan?LQ?was the largest.The results of STRUCTURE showed that when K was two,261 D.cercidifolius var.longipes individuals clustered into 2 groups.Dao county?DX?,Mang Shan?MS?,Yi Zhang?YZ?,Lian Zhou?LZ?,Shao Yang?SY?,Xin Ning?XN?,Yi Feng?YF?and Yi Huang?YH?were a group.Long Quan?LQ?,Kai Hua?KH?,Yu Shan?YS?and Jing Gang Ghan?JGS?were a group.The results of correlation test of geographical distance and genetic distance showed that there was no significant correlation between genetic distance and geographical distance.