Chromosome and Molecular Analyses Reveal Significant Karyotype Diversity and Provide New Evidence on the Origin of .

Zhuk. is tetraploid grass species (2n = 4x = 28, UUXX) closely related to and growing in Western Asia and a western part of the Fertile Crescent. Genetic diversity of was assessed using C-banding, FISH, nuclear and chloroplast (cp) DNA analyses, and gliadin electrophoresis. Cytogenetically was subdivided into two groups, C-I and C-II, showing different karyotype structure, C-banding, and FISH patterns. C-I group was more similar to . All types of markers revealed significant heterogeneity in C-II group, although group C-I was also polymorphic. Two chromosomal groups were consistent with plastogroups identified in a current study based on sequencing of three chloroplast intergenic spacer regions. The similarity of group C-I of with and their distinctness from C-II indicate that divergence of the C-I group was associated with minor genome modifications. Group C-II could emerge from C-I relatively recently, probably due to introgression from another species followed by a reorganization of the parental genomes. Most C-II accessions were collected from a very narrow geographic region, and they might originate from a common ancestor. We suggest that the C-II group is at the initial stage of species divergence and undergoing an extensive speciation process.