Cytogenetic Study in some Species of Stipagrostis

In the present investigation، eight accessions belonging to three species of Stipagrostis were subjected to cytogenetic analyses. Results of chromosome count showed two ploidy levels of diploid (2n=2x=22) in S. plumosa and tetraploid (2n=4x=44) in S. pennata and S. karelinii. The chromosome number (tetraploid) of S. karelini is reported for the first time. Karyotypic formula obtained in the studied populations mostly included metacentric chromosomes. Satellite and nucleolus organizer region (NOR) were observed in diploid populations of S. plumosa. Karyotypic analysis and grouping of karyotypes with Stebbins method classified diploid population into 1A and 2A and tetraploid populations into 1B karyotypic classes. Considering this classification it could deduced that tetraploid populations containing asymmetrical karyotype. Analysis of variance of karyotypic traits showed significant differences for short arm length، arm ratio and centromeric index that indicating chromosomal variation among the studied genotypes. The highest correlations were observed between short arm with long arm، centromeric index with total form percentages and centromeric index with value of relative chromatin content (r = 0. 96، 0. 88 and 0. 87، respectively). The results of cluster analysis and Romero Zarco coefficient grouping were consistent and divided the populations into two separate groups. First group included three diploid populations from S. plumosa and the second group included tetraploid populations from S. pennata and S. karelinii species.