Abstract
In this study, chromosome numbers, ploidy levels and karyotype criteria of 23 taxa representing 13 Astragalus species from different ecological regions of Iran were analyzed and discussed. The basic chromosome number was found as x=8 and all the studied taxa were diploid, tetraploid or hexaploid. Among the species, eighteen were diploid (2n= 16), four were tetraploid (2n=32) and one was hexaploid (2n=48). The karyotype in the studied taxa was mostly comprised of metacentric to submetacentric chromosomes as indicated by their mean arm ratio that ranged between 1.376 in A. megalotropis (in accession 14929) and 2.453 in A. vegetus (in accession 3421). The degrees of karyotype asymmetry were indicated by the values of A¹ ranging between 0.236 in A. megalotropis (in accession 14929) and 0.540 in A. vegetus (in accession 3421) , and the values of TF%, ranging between 30.697 in A. vegetus (in accession 3421) and 42.50 0 in A. megalotropis (in accession 14929). Based on the values of A¹, TF% and karyotype formula, A. vegetus (accession 3421) and A. megalotropis (accession 14929) had an asymmetric and symmetric karyotype respectively. The chromosomes in the studied species of Astragalus were generally small with mean sizes ranging between 2.475 and 4.515 μm. Shorter chromosomes were found in A. aduncus (in accession 14995, TL=2.475 μm), A. vanilla (in accession 13764, TL=2.670 μm) and A. dactylocarpus (in accession 1734, TL=2.743 μm), whereas longer chromosomes were recognised in A. vegetus (in accession 25786, TL=4.515 μm). Based on the analyses of karyotype features, the relationships among the taxa were constructed using PCA analysis. The grouping of the species examined in these plots is discussed in the light of their traditional systematic classification.
