Systematics Relationships Of Leymus (Poaceae: Trticeae) By Molecular Markers

Leymus Hochst.is an important perennial genus of Triticeae Dumortier(Poaceae). It includes about 30 species and 19 subspecies.They are distributed in the coastal areas of North Sea,Central Asia,East Asia,extending to Alaska and the western areas of North America.They are found in particularly large numbers on the mountains of Central Asia and North America.Formerly,it included about 10 species recorded in China.In addition to some new taxon reported in recent years,it includes about 25 species,4 subspecies and 3 varieties,which are mainly distributed in north-western, north,north-eastern and south-western regions in China.Many species of Leymus are not only main components of grasslands and grass marshlands,but also fine varieties of herbage and forge.Growing in saline or alkaline lands,and dry or semi-dry areas,some species are highly adaptable to coldness,dryness and saline or alkaline lands.And some species bear such desirable traits as disease and insect resistance,bigger spikes,more and bigger grains and efficient photosynthesis.Being an important genetic resource, Leymus is of significance to improvement of Triticeae cereal crops.However,the origin and definition of the genus,precise taxonomic ranks and relationships among the species in the genus have been under discussion.The study on genetic diversity of Leymus would provide theoretical foundation for using this genus plants to breed Triticeae crops and herbage.The present study systematically evaluated the systematics relationships of Leymus on isoenzyme,gliadin and RAPD molecular level,and investigated the parental Psathyrostachys ancestries which offered the Ns genome to Leymus and to elucidate the origins of another base genome of Leymus.The main results showed as following:1.The esterase isozyme(EST) and superoxide isozyme(SOD) of 24 species of Leymus,Australopyrum,Agropyron,Lophopyrum,Pseudoroegneria,Psathyrostachys and Hordeum in triticeae were analyzed by using polyacrylamid gel electrophoresis (PAGE) technique.The results show as follows:â‘ All the 24 species have significant isozymes polymorphism,a total of 45 bands are separted;â‘¡The relationship between L.chinensis and the other 13 species of Leymus is remote,while it is close to Hordeum bogdanii,Psathyrostachys juncea and the species of Leymus have closer relationship;â‘¢The species of those which contain similar genomes are clustered together;â‘£The results of isozymes analysis are basically comparable with those obtained from studies on cytology and morphology.2.The gliadin of 22 materials of Leymus,Australopyrum,Agropyron, Lophopyrum,Pseudoroegneria,Psathyrostachys and Hordeum in Triticeae were analyzed by using acid-polyacrylamide gel electrophoresis(A-PAGE).The results show as follows:â‘ All the 22 materials have significant gliadin polymorphism.A total of 52 bands are separated,and the gliadin ploymorphism amounts to 100%.It shows that there is plentiful polymorphism between these genera and species;â‘¡The relationship between Psathyrostachys juncea and Psa.huashanica is remote,while Psa.juncea and the species of Leymus have closer relationship;â‘¢The species of those which contain similar genomes are clustered together,which suggests they have closer relationship;â‘£The results of gliadin analysis are basically comparable with those obtained from studies on cytology and morphology,which shows that the gliadin patterns is usefulness in the systematic studies of those perennial species in Triticeae.3.Six genome-specific RAPD markers representing Ns,E,W,P,St,H genome respectively were utilized to determine the genome relationships among Leymus and its related species.The results indicated that:the Ns genome-specific RAPD marker presented in 14 polyploid species of Leymus,while the E and P genome-specific RAPD markers absent in 14 polyploid species of Leymus;â‘¡the W genome-specific RAPD marker presented in L.ramosus;the St genome-specific RAPD marker presented in L.triticoides,L.ramosus,L.paboanus,L.chinensis,L. pseudoracemosuss;the H genome-specific RAPD marker presented in L.angustus,L. arenarius,L.multicaulis,L.karelinii,L.tianshanicus,L.paboanus,L.cinereus,L. chinensis,L.racemosus;â‘¢L.paboanus and L.chinensis had the specific bands of Ns genome,H genome and St genome;L.ramosus had the specific bands of Ns genomes, St genomes and W genomes.Based on these results from this study,we can draw conclusions that:Leymus species have multiple origins.Ns genome arose from the genus Psathyrostachys, While Psa.juncea and the species of Leymus have closer relationship.E and P genome absent in Leymus,While the partial species of Leymus had close phylogenetic relationship with St,W and H genome.