Submitted to: Euphytica
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/13/2005
Publication Date: 11/30/2005
Citation: Tuna, M., Vogel, K.P., Arumuganathan, K. 2005. Cytogenetic characterization of tetraploid bromus ciliatus genome. Euphytica 146:177-182. Interpretive Summary: Fringed brome, Bromus ciliatus, is a bromegrass that is native to North America. The objective of this study was to determine its nuclear DNA content, characterize its chromosomes using cytogenetic analyses, and compare it to European bromegrass using this information. The results show that tetraploid B. ciliatus has 14 pairs of chromosomes that can be clearly distinguished from each other and its DNA content is significantly larger than that of the European bromegrasses with the same number of chromosomes. These results indictate that Bromus ciliatus originated from two different diploid Bromus species making it an allotetraploid and it likely has different genomes than the European Bromus species evaluated to date.
Technical Abstract: Tetraploid Bromus ciliatus L. is a North American bromegrass. The objective of this study was to characterize the genome of the tetraploid B. ciliatus by cytogenetic methods and compare it to the genomes of the other species included in the genus section Pnigma. All examined plants of the accession (USDA PI 232214) were tetraploids (2n = 28). The mean 2C nuclear DNA content for tetraploid B. ciliatus was 19.13 ± 0.07pg as determined by flow cytometry which is significantly greater than the tetraploid DNA content of tetraploid B. inermis Leyss. (2C = 11.74± 0.16pg). C-banding procedures were used to identify individual mitotic chromosomes and to develop a karyotype for B. ciliatus. The genome of the tetraploid B. ciliatus consisted of 16 median chromosomes, 8 submedian chromosomes and 4 chromosomes with satellites including one pair with a large satellite and one pair with a small satellite. The general pattern of the distribution of constitutive heterochromatin in B. ciliatus was quite different than the other bromegrasses that have been analyzed to date. Except for two pairs of chromosomes, all chromosomes in tetraploid B. ciliatus had telomeric bands on one or both arms. Some of the chromosomes with telomeric bands had centromeric bands situated at one or both sides of the centromere and intercalary bands which were generally absent in the other bromegrass species. It was possible to identify all chromosomes of tetraploid B. ciliatus and to match the pairs of homologous chromosomes by using chromosome lengths, arm length ratios and C-banding patterns. The results of this study indicate that tetraploid B. ciliatus is an allotetraploid and likely has different genomes than the European Bromus species evaluated to date.