Phylogeoraphy And Genetic Diversity Of Paulownia Fortunei

Paulownia fortunei belongs to Paulownia genus of Scrophulariaceae.In the plant germplasm resources of China,Paulownia fortunei is a excellent fast-growing species among the genus of Paulownia trees,which has a fast growth,fine stem form,tall tree,disease resistance and other characteristics.The natural distribution area of Paulownia fortunei in 20°-30° N,100°-122° E,widely distributed south of the Yangtze River.Based on investigation and collection of Paulownia fortunei germplasm resources.the genetic differentiation and genetic diversity of Paulownia fortunei population were analyzed.Besides,the research analyzed geographic pattern of haplotypes,which can help to infer glacial refuge and the postglacial migration route.The research can help researchers to understand genetic structure and the historical process of geographical distribution pattern.And the protection and utilization of population genetic resources has more important significance.The results are as follows:In this day,three different chloroplast gene fragments of rpl16,atpB-rbcl,trbv-ndhc were adopted,and the ITS fragment of nrDNA to sequence respectively in 26 populations of Paulownia fortunei.12 haplotypes in cpDNA sequences and 7 haplotypes in ITS sequences from Paulowniafortunei were obtained.The result of the research showed that the haplotype diversity of Paulownia fortunei in species level,the genetic variation mainly existed whthin the population and the degree of geneticdifferentiation was obvious.The unimodal curve of mismatch distribution analysis,the beast analysis and the star-shaped haplotype analysis network accepted that rapid population expanded and haplotype differences were significant(Nst>Gst,p<0.01)among the populations of Paulownia fortunei,indicating there are obvious phylogeographical pattern in its distribution area.The differentiation time of Paulownia fortunei began in the middle of the Quaternary Pleistocene.From the time scale,the intraspecific differentiation time of Paulownia fortunei may be rapid formation and expansion that it related to the global warming after the Pleistocene.This study speculated that Paulownia fortunei has two shelters,one for hording area of the Chongqing,Hubei and Hunan provinces,one for bording area of Guangxi Hechi and Guizhou Duyun.After the glacial period,Paulownia fortunei migrated from center of origin in East Sichuan and West Hubei area,eastward moved into Hunan and Anhui along the Yangtze River,and then into Zhejiang province;southward moved into Guangxi,Guizhou,and then into the territory of Fujian and Guangzhou.The phylogenetic tree constructed from two chloroplast DNA fragments showed that three populations of Paulownia fortunei belonged to the same species.Therefore,the study indicated that Paulownia fortunei was indeed an independent and stable species in Paulownia genus.The AFLP molecular markers were used to analyze the genetic diversity of 26 populations of Paulownia fortunei.A total of 9 pairs of primer combinations were screened out and 1169 polymorphic loci were amplified.The average number of amplified bands per pair of primers was129.9,The percentage of effective bands was 97.96%,the number of effective alleles was 1.2138-1.2726,Nei gene diversity index was 0.1566-0.1887,Shannon information index was 0.2692-0.3117,which indicated genetic diversity and different among populations of Paulownia fortunei.From the results of molecular variance analysis(AMOVA),it was found that the genetic diversity of Paulownia fortunei was 5.96%and 94.04%of the total variation,respectively,which indicated that the genetic diversity of Paulownia fortunei existed mainly within the population.The 26 populations of Paulownia fortunei were divided by unweighted pair-group method with arithmetic means(UPGMA)into 4 groups with obvious regionalism,in which the populations with close geographical locations(latitude)were clustered together.From the species level of Paulownia fortunei,the genetic variation of the population mainly was intra-population,and the genetic information provided by the intra-population phylogeography of Paulownia fortunei plays an important role in the protection of the genetic diversity of its species.Through the analysis of the chloroplast haplotypes And ITS haplotypes analysis from rare haplotypes and specific haplotypes in the natural evolution and frequent human activities under the influence of the loss is easy,so this populations of Paulownia fortunei should be preserved in the local ecological environment to avoid the growth of the environment changes and result in the loss of haplotypes.For the high haplotype diversity and genetic diversity,individuals with fewer populations,It's essential to protect the purity of the species from cross regional conservation.