Molecular-cytogenetic analysis of diploid wheatgrass Thinopyrum bessarabicum (Savul. and Rayss) A. Löve

Thinopyrum bessarabicum(T. Săvulescu & T. Rayss, 1923) A. Löve, 1980 is diploid (2n=2x=14, JJ or EbEb), perennial self-fertilizing rhizomatous maritime beach grass, which is phylogenetically close to another diploid wheatgrass species,Agropyron elongatum(N. Host, 1797) P. de Beauvois, 1812. The detailed karyotype ofTh. bessarabicumwas constructed based on FISH with six DNA probes representing 5S and 45S rRNA gene families and four tandem repeats. We found that the combination of pAesp_SAT86 (= pTa-713) probe with pSc119.2 or pAs1/ pTa-535 allows the precise identification of all J-genome chromosomes. Comparison of our data with the results of other authors showed that karyotypicallyTh. bessarabicumis distinct fromA. elongatum. On the other hand, differences between the J-genome chromosomes ofTh. bessarabicumand the chromosomes of hexaploidTh. intermedium(N. Host, 1797) M. Barkworth & D.R. Dewey, 1985 and decaploidTh. ponticum(J. Podpěra, 1902) Z.–W. Liu & R.–C. Wang, 1993 in the distribution of rDNA loci and hybridization patterns of pSc119.2 and pAs1 probes could be an indicative of (1) this diploid species was probably not involved in the origin of these polyploids or (2) it could has contributed the J-genome toTh. intermediumandTh. ponticum, but it was substantially modified over the course of speciation