Studies On Karyotypic Variations Of Agropyron Cristatum (L.) Gaertner Populations

Agropyron cristatum (L.) Gaertner. a perennial herb of Triticeae in Gramineae, is the type species of the genus Agropyron Gaertner. It possesses strong adaptability and can be used as soil and water conservation and landscaping plants in arid areas. Geographically, A. cristatum is widely distributed in Eurasia. Extensive researches have been focused on morphology, molecular and physiological. However, ploidy of A. cristatum is still a lack of systematic and comprehensive research. Karyotypic variations of A. cristatum remain unclear in different geographic distributions and ecological environments. The genetic relationships and evolutionary trends among distinct A cristatum populations are short of studies.In this study, A. cristatum (60 materials) were collected from four natural distribution areas. The aims of this study were to:(1) study preliminarily karyotypical variations of A. cristatum; (2) reveal genetic relationships, origin and evolution by karyotype, evolutionary trend and cluster analyses. The main results are as follows:1. The karyotype analysis of A. cristatum displayed that there existed eight diploid (2n=2x=14),50 tetraploid (2n=4x=28), one hexaploid (2n=6x=42) and one aneuploid (2n=4x+1=29).2. Chromosome karyotype consisted of metacentric chromosomes (m) and submetacentric chromosomes (sm). The mean arm ratio of A. cristatum varied from 1.38 to 1.61, chromosome length ratio varied from 1.32 to 1.97, percent of chromosomes whose arm ratio are more than 2:1 ranged from 0 to 0.29, karyotype asymmetry index of ranged from 57.74% to 61.46%. The karyotype belonged to 1A and 2A types.3. The karyotype evolution trend elluminated that European population origin at the latest and evolutionary higher; Central Asia and the Tibetan Plateau populations relatively early origin and the earliest populations of Central Asia and evolution lower. It suggested that the central Asia could be the center of origin of A. cristatum.4. Cluster analysis manifested that A. cristatum were approximately divided into three clades, as follows:Clade ? and Clade ? included A. cristatum from Central Asia, East Asia and the Tibetan Plateau populations. Clade III contained all of the European population and parts of the Central Asia population. Three-dimensional scatter plot analysis of A. cristatum reflected similar genetic relationship as Cluster analysis. Thus, we speculated the A. cristatum populations of Central Asia, East Asia and the Tibetan Plateau had closer genetic relationships, European and Central Asia had closer genetic relationships.5. Comprehensive analysis suggested that chromosome karyotypic variations of A. cristatum may be closely related to the distribution of different habitats. The A. cristatum Central Asia population may be the original centre and diffused to East Asia, the Tibetan Plateau and Europe populations.