Genome Constitution Of Elymus Atratus(Nevski) Hand.-Mazz.and E.Purpuraristatus C.P.Wang Et H.L.Yang(Poaceae:Triticeae) Inferred From Meiotic Pairing Behavior And Genomic In Situ Hybridization

Elymus L.sensu lato is a very important perennial genus of the tribe Triticeae(Poaceae),and mainly distribute in the South,North America,Eurasia and Africa.Elymus is a very big and polymorphic genus,and all the species in this genus are morphologically different from each other.Elymus L.s.1.includeds tetraploid,hexaploid and octaploid species with the different genome combinations of St,H,Y,P,and W genome.However,Elymus L.sensu strictus contains tetraploid,hexaploid species with genome composition of StH.Campeiostachys Brobov is a taxa separated from Elymus L.and contains hexaploid species with genome composition of StYH.Elymus L.and Campeiostachys Drobov are not distinguishable from the point of morphology,but the two genera are completely different from the origin of the system.The main reason is that the recessive gene of the Y chromosome was not expressed,both of which are expressed in the species traits of St and H.Therefore,this reason leads to the misclassification of many species into Elymus L.Elymus atratus(Nevski)Hand.-Mazz.and E.purpuraristatus C.P.Wang et H.L.Yang were treated as the suspicious taxonomic groups of Elymus L.by Yen and Yang in 2013.The genome compositions of these two species are not yet clear and their exact status can not be determined,pending the relevant experimental analysis of the findings to determine their attribution.The purpose of this paper is to study the genome constitution and classification of these two species,the main objectives are:(1)to hybridize E.atratus and E.pururaristatus with the other Elymus species with known genome constitutions,and to determine the genome composition of two species by observing and analyzing the chromosome pairing at the meiotic metaphase I of the pollen cell of hybrid F1;(2)to validate their genome compositions by using the genome in situ hybridization,and to make the taxonomical treatment.The main results are as follows:1.The chromosome pairing at the meiotic metaphase I of interspecific hybrid F1 from E.atratus were observed.An average of 19.21 bivalents from E.atratus × E.tangutorum(2n = 6x = 42,StYH),indicate the genome constitution of E.atratus isStYH.2.The monochromatic genomic in situ hybridization analysis of E.atratus using the H genomic DNA of Hordeum bogdanii and the StY genomic DNA of Roegneria ciliaris as mutual probe and block,indicate that E.atratus is a hexaploid species and the genome constitution is StYH.3.The chromosome pairing at the meiotic metaphase I of interspecific hybrids F1 from E.purpuraristatus were observed.An average of 12.80 bivalents from E.wawawaiensis(2n = 4x = 28,StH)×E.purpuraristatus indicate the genome composition of E.purpuraristatus is StH;(2)an average of 19.11 bivalents from E.purpuraristatus×E.tangutorum(2n = 6x = 42,StYH),indicates that the genome constitution of E.purpuraristatus is StYH.4.The monochromatic and two-color genomic in situ hybridization analysis of E.purpuraristatus was carried out by using the H genomic DNA of Hordeum bogdanii and the StY genomic DNA of Roegneria ciliaris as mutual probe and block,and using the H genomic DNA of H.bogdanii and the St genomic DNA of Pse.libanotica as probe simultaneously.The results indicate that E.purpuraristatus is a hexaploid species and the genome constitution is StYH.5.According to the results of chromosome pairing at meiotic metaphase I and GISH,Elymus atratus and E.purpuraristatus are hexaploid species,and the genome constitution is StYH.On the basis of the principle of genome classification in the tribe Triticeae,these two species should be treated as the species in the genus Campeiostachys Drobov.Their taxonomical treatments are Campeiostachys atrata(Nevski)Y.H.Zhou,H.Q.Zhang et W.H.Chen and Campeiostachys dahurica(Turcz.ex Griseb.)B.R.Baum,J.L.Yang et C.Yen var.purpuraristata(C.P.Wang et H.L.Yang)Y.H.Zhou,H.Q.Zhang et W.H.Chen.