Genetic Differentiation Of Elymus Sibiricus L.Based On Karyotype And 45S RDNA Studies

Elymus sibiricus L.as the type species of genus Elymus,is a perennial,self-pollinating and allotetraploidgrass 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,serving as an important forage species,is widely used in cultivated pastures and natural grassland due to excellent cold/drought tolerance,good forage quality and adaptability.Previous investigation focuseedd on the cultivar,biochemistry and molecular biologyof E.sibiricus.The information of genetic relationship,even genetic distance between populations and geographical distribution reports is still lacking.In this study,four populations of E.sibiricusincluding 15 accessions fromCentral Asia,East Asia,Qinghai-Tibet Plateau and Europewere analyzed using karyotype,GISH,45S rDNA FISH and ITS sequence information.The main results showed as follows:Chromosome karyotype from 15 accessions of E.sibiricus consisted of metacentric chromosomes(m)and submetacentric chromosomes(sm).The karyotype differences were mainly reflected in the karyotype parameters.Chromosome length ratiovaried from 1.3862?1.8635,and karyotype asymmetry index of ranged from 54.85%?59.33%.Thus,two karyotypes,1A and 2A,exist in these populations.The evolutionary trend showed that the East Asian population appears large differences within the populations with the higher evolutionary trend,Qinghai Tibet populations is in specific small difference within the group with the not high evolutionary trend,and the difference in Central Asia Group is the largest with the highest evolutionary trendThe numberof 45S rDNA sites range from 8 to 10 in E.sibiricus from Qinghai-Tibet Plateau population and East Asia population.Six sites were observedin Central Asia population.However,4 sites were investigated in Europe population.Most of these sites distributed in the terminal regionsand interstitial-terminal of the short arms.There were differences in the number and distribution of the sites in different populations,which suggested that 45 S rDNA sites are polymorphism in E.sibiricus from different geographical distribution,losing or gaining of the 45 S rDNA site due to the interaction of its environmental conditions.The populations of Qinghai-Tibet Plateau and East Asia are close relationship.Comparing the numbers and locations in 45S rDNA for allopolyploid and its putative diploid donor,we found that E.sibiricus is allopolyploid.45S rDNA loci were preserved in the St and H genome of PI442485(European).While,45S sites of rDNA signaling was only observed in St genome of other materials.The differences of the number of sites were:1)The doubling of genes caused by non genome doubling or the recombination of homologous chromosomes;2)theco-evolution and partial similarity of chromosomes in the evolution of body weight after convergence leads to the same sequence.Based on nrDNA ITS sequences,phylogenetic analysis was performed on 15 E.sibiricus.The results suggestedthat 14 of 15 tend to St type,and oneE.sibiricusfrom Europe is inclined to H type.Incomplete concerted evolution lead to the occurrence of St polyploid bias,inferring that E.sibiricus exist its orientation during evolution.E.sibiricus in Europe population perfers to leaning to H type.E.sibiricus in Qinghai-Tibet Plateau,East Asia and Central Asia,however,tend to chase to St type.Therefore,the evolutionary directions of ITS sequence vary from in different populations of Elymus.