| Elymus sibiricus L.,as the type species of genus Elymus,is a perennial,self-pollinating and allotetraploid grass with St and H genome.It is widely distributed in Central Asia,Russian,Europe,Mongolia,China and even to parts of North America.The habitats of this species prefer wet meadows and among open forest or shrubs.E.sibiricus in a large collection of excellent genes,such as disease resistance gene and stress resistance gene,are valuable genetic resources for the genetic improvement of wheat.Serving as an important forage species,E.sibiricus is widely used in cultivated pastures and natural grassland due to excellent cold/drought tolerance,good forage quality and adaptability.Therefore,the study of E.sibiricus not only contribute to the development of grass industry and animal husbandry,but also benefit to genetic improvement of wheat.In recent years,studies on the morphology,cytology,cytogenetics,and molecular phylogeny of E.sibiricus have shown that E.sibiricum with StH genomes,which originated from hybridization between the species from Pseudoroegneria(St genome)and Hordeum(H genome).It with wide geographical distribution and great morphological variation.However,the origin of E.sibiricus is still unclear,the reasons for its abundant genetic diversity have not been clarified,and the reasons for its existing geographical distribution pattern have not been explored.In this study,we investigated the genetic diversity and distribution patterm of E.sibiricus based on trnL-F and psbA-trnH sequences infromation.The main results showed as follows:1.The combine sequences were analyzed for 87 E.sibiricus,together with 3Hordeum accessions and 3 Pseudoroegneria accessions.It is suggested that:(1)the St genome may be served as potential maternal donor.(2)The origin of its maternal donor may be related to geographical distribution.2.Based on trnL-F and psbA-trnH sequences to analyze genetic diversity and genetic relationship among eighty-seven E.sibiricus.Nucleotide diversity and haplotype diversity are ?=0.0207,and Hd=0.9990 respectively.It showed that the genetic diversity within the accessions were fairly high.The total genetic diversityacross all accession was 0.462,it revealed 53.8% of the total variation resided among population,and 46.2% resided within populations.It is suggested that inter-population genetic variation has effect on the genetic diversity of E.sibiricus.3.Based on Tajima's D test result is significant and doesn't follow the neutral evolution model.It indicated that E.sibiricus had experienced a population expansion event in the history of evolution.The value of genetic diversity and genetic distance between central Asia group and other groups indicated that the central Asia group had higher genetic diversity,and different accession of E.sibiricus population from Central Asia were scattered in different subclades.The result indicated that Central Asia may be the origin center and the refuge of E.sibiricus during the last glacial period.4.Based on the niche modeling analysis and the maximum entropy model prediction of E.sibiricus.The result showed that:(1)the existing pedigree geographical structure of E.sibiricus may be due to Central Asia group diffused to East Asia,the Tibetan Plateau and Europe after the glacial period.(2)In the future,the distribution of E.sibiricus shows a trend of expansion.Central Asia's distribution spreads slightly to the north,while Europe's distribution moves to the west,this phenomenon may be caused by global warming. |
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