Research Of Genomic Relationship And Genome Size Of Elymus L.on The Qinghai-Tibet Plateau

Elymus is an important allopolyploid taxa belonging to Triticeae in Poaceae family as well as important germplasm resources in wheat breeding,which has many scarce excellent stress resistance genes such as cold,drought tolerance and disease resistance.Altitude affects polyploidization and hybridization-differentiation and genome size variations leading to plant genetic evolution,providing more genetic evidence for mechanisms to adapting altitude in Elymus and having significant value in germplasm resources protection and collection.Our report analysed the influence of altitude on the genetic evolution of Elymus according to 27 populations sampled from 9 altitudes(3000-4300 m)on the Qinghai-Tibetan Plateau.Firstly,we used flow cytometry PI staining technique to determinate the genome size of Elymus and E.nutans was found to have a genome size of 9.54 Gb while E.sibiricus and E.burchan-buddae were observed to have genome sizes of 8.29 and 6.10 Gb respectively.Maximum genome size differences among populations for E.nutans(2.03 Gb,23.82%)and E.sibiricus(1.64 Gb,21.61%)supported for separation between populations,however E.burchan-buddae(0.9 Gb,16.45%)supported genome constancy.Hexaploid has a larger and more complex genome and stronger heredity and mutations.ANOVA analysis indicated genome size variations along altitude among populations of E.nutans and E.sibiricus were statistically significant while nonsignificant differences were revealed in E.burchan-buddae.However,there was no significant correlation between intra-population genome size variation and morphological variables with Spearman rank correlations.Adittionally,the observation of pairing situation of chromosomes and probe in genomic in situ hybridization mitotic metaphase showed the genetic relationship between Elymus species,providing guarantee to study the origin and evolution of the genomes.When total DNA probe from Pseudoroegneria strigosa was hybridized to chromosome preparations of Elymus,we observed strong in all three Elymus species.The strong hybridization red fluorescence signals were clustered on 20-24 chromosomes of E.burchan-buddae,there are only 18-22 chromosomes with fluorescent signals for E.Sibiricus and 26-32 bright hybridization signals revealed in E.nutans,which can distinguish St and Y,St and H genomes.The same in situ hybridization pattern was obtained when using total DNA probe from Hordeum bogdanii wilensky on chromosomes of E.burchan-buddae,8-12 chromosomes showed green fluorescence signals while there are 18-22,and 20-26 chromosomes signals in E.sibiricus and E.nutans,resulating differentiaion between Y and H genomes.We concluded the relationship between the St genome and the Y genome was closer than the St genome and the H genome.Based on ANOVA,we found significant genome differentiation along altitude in hexaploid E.nutans and tetraploid E.burchan-buddae with Pseudoroegneria strigosa and Hordeum bogdanii wilensky as probes respectively,but no significant differences in tetraploid E.sibiricus were found.However,variation of genomic hybridization among individuals of the same population was greater in the medium altitudes(3400-3900 m)than the low(3000-3400 m)and the high(3900-4300 m)altitudes.