Karyotype and C-banding patterns of mitotic chromosomes in diploid bromegrass (Bromus riparius Rehm)

Previous cytogenetic studies of the genus Bromus L. were limited to chromos ome counts and construction of karyotypes on the basis of Feulgen staining. Since the chromosomes of Bromus are similar in morphology, these karyotype s are of limited use for chromosome identification and genome analysis. The objectives of this study were to develop and evaluate a Giemsa C-banding p rocedure to use in identification of individual bromegrass chromosomes and to develop a karyotype for diploid Bromus riparius Rehm. (2n = 14; PI 44021 5). All chromosomes had one or more C-bands which were located mainly at te lomeric regions. A group (I) of four pairs of chromosomes had telomeric ban ds on only one arm and could be differentiated. In this group, one pair had an interstitial C-band along with a telomeric band, one pair had a nucleol us organizer region (NOR) at a subtelomeric location on the short arm, and the other two pair could be distinguished by centromere location. The other group (II) of three pairs or chromosomes had telomeric bands on both arms. The unequivocal identification of specific chromosomes of Group II was not possible in all cells because of their similarity and differential condens ation of chromosomes. Chromosomes of both groups were either metacentric or submetacentric. The total length of individual chromosomes ranged from 5.5 8 to 6.87 mum and the arm ratios ranged from 1.02 to 1.5. The homologous ch romosomes were paired and assigned numbers I to VII in decreasing length. A karyotype was constructed by means of the C-bands, mean chromosome lengths , and arm ratios. The C-banding procedure used in this study could be used to developed karyotypes for the other species of the genus Bromus and these C-banded karyotypes could be used to compare genomes within the genus.