Phylogenetic Relationships Between Leymus And Related Diploid Triticeae Species Based On RAPD And SSR Markers

Leymus Hochst. is an important perennial genus of Triticeae Dumortier (Poaceae). It includes about30species and19subspecies. 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. There are many Leymus species in China and it includes about27species,3subspecies and3varieties, 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 RAPD and SSR molecular markers, 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 phylogenetic relatioships among13Leymus species and4Pseudoroegneria species,3Psathyrostachys species,2Agropyron species,2Hordeum species, Australopyrum retrofractum, Lophyrum elongatum, Hystrix patula were analyzed by using RAPD molecular markers. A total of156products were amplified by2410-mer arbitrary primers, among which154products (98.72%) were found to be polymorphic.2-10product bands were amplified by each primer, with an average of6.5bands.1-10polymorphic bands were amplified by each primer, with an average of6.42bands. The data of156RAPD bands were used to generate Jaccard’s similarity coefficients and to construct a dendrogram by means of UPGMA in the NTSYS-pc computer program. The results showed as follows:(1) The13Leymus species were clustered together, and there is closer relationship between Leymus akmolinensis and L. angustus. it same as L. pseudoracemosus and L. racemosus.(2) There are closer relationships among Psathyrostachys huanshanica, Psa. juncea. Agropyron critatum, Ag. Mongolicum, Hordeum chilense, Australopyrum retrofractum, Hystrix patula, Lophyrum elongatum and Leymus species, while the relationships among Pseudoroegneria species, H. bogdanii, Psa. fragilis and Leymus species are remote.2. The phylogenetic relatioships among12Leymus species and4Pseudoroegneria species,3Psathyrostachys species,2Agropyron species,2Hordeum species, Australopyrum retrofractum, Lophyrum elongatum, Hystrix patula were analyzed by using SSR molecular markers. A total of187products were amplified by23pairs of specific SSR primers, among which184products (98.39%) were found to be polymorphic.2-16product bands were amplified by each pair primers, with an average of8.13bands.2-16polymorphic bands were amplified by each pair primers, with an average of8.0bands. The data of187SSR bands were used to generate Jaccard’s similarity coefficients and to construct a dendrogram by means of UPGMA in the NTSYS-pc computer program. The results showed as follows:(1) Except L. multicaulis, the other11Leymus species were clustered together, and there are closer relationships among L. racemosus、L. tianshanicus、L. secalinus and L. triticoides.(2) L. multicaulis was clustered with Hystrix patula and related diploid Triticeae species.(3) The relationship between Hystrix patula and Leymus species is remote.3. RAPD and SSR molecular markers results indicated that Leymus species have Ns genome, which come from Psathyrostachys, and different Psathyrostachys species could seve as the donor for different Leymus species. The partial species of Leymus has close phylogenetic relationship with Hordeum chilense, Australopyrum retrofractum, Lophyrum elongatum, while St genome absent in Leymus.