Biosystematic Studies On Leymus Chinensis, L. Multicaulis And L. Secalinus (Poaceae: Triticeae)

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,and extended 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.Now it includes about 25 species,4 subspecies and 3 varieties,which are mainly distributed in north-western, north,north-eastern and south-western regions of China.Many species of Leymus are not only main components of grasslands and grass marshlands,but also fine varieties of herbage and forage.They are growing in saline or alkaline lands,dry or semi-dry areas.Some species of Leymus are highly adaptable to coldness,dryness and saline or alkaline lands,while 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 improve 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 the Leymus in cereal breeding.The aims of the present paper is to evaluate the relationship of the three species including Leymus chinensis,L.multicaulis and L.secalinus,and the relationship between Leymus species and Psathyrostachys species,according to morphological comparison,meiotic and fertility studies.The main results showed as follows:1.L.chinensis,L.multicaulis and L.secalinus showed different morphological characteristics,such as plant height and panicle.2.Chromosome pairing behavior in meiosis of hybrids,L.multicaulis(PI 499520)×L. chinensis(PI 499515) andL.multicaulis(PI 499520)×L.chinensis(PI 499514) formed an average of 12.26 and 10.14 bivalents per cell,respectively;chromosome pairing of hybrids of L.multicaulis(PI 440324)×L.secalinus(Y040) and L.multicaulis(PI 440325)×L. secalinus(Y040) formed an average of 12.78 and 13.16 bivalents per cell,respectively.The results suggest that the three Leymus species contain the same genome constitutions,NsXm.3.Chromosome pairing of hybrids of L.multicaulis(PI 499520)×L.chinensis(PI 499515) formed an average of 12.26 bivalents per cell,with a C-value of 0.72;L.multicaulis (PI 499520)×L.chinensis(PI 499514) formed an average of 10.14 bivalents and 0.04 trivalent per cell,with a C-value of 0.60.The results suggest that genome differentiation occurred between the two populations of L.chinensis.4.Chromosome pairing of hybrids of L.multicaulis(PI 440324)×L.secalinus(Y040) and L.multicaulis(PI 440325)×L.secalinus(Y040) formed an average of 12.78 and 13.16 bivalents per cell,with C-values of 0.80 and 0.82,respectively.The results indicate that a degree of variations existed between the two populations of L.multicaulis.5.Chromosome pairing of hybrids of L.chinensis×Psa.huashanica formed an average of 8.26 bivalents per cell,with C-values of 0.94.In the 50 cells that observed,1 trivalent exisited in 1%of them.The results suggest that L.chinensis contains a set of Ns genome from Psathyrostachys,while the other set of genome might have homoelogy with the Ns genome.