title: Karyotype and nuclear DNA content of hexa-, octo-, and duodecaploid lines of Bromus subgen. Ceratochloa.
abstract: The subgenus Ceratochloa of the genus Bromus includes a number of closely related allopolyploid forms or species that present a difficult taxonomic problem. The present work combines data concerning chromosome length, heterochromatin distribution and nuclear genome size of different 6x, 8x and 12x accessions in this subgenus. Special attention is paid to the karyotype structure and genomic constitution of duodecaploid plants recently found in South America. Hexaploid lineages possess six almost indistinguishable genomes and a nuclear DNA content between 12.72 pg and 15.10 pg (mean 1Cx value = 2.32 pg), whereas octoploid lineages contain the same six genomes (AABBCC) plus two that are characterized by longer chromosomes and a greater DNA content (1Cx = 4.47 pg). Two duodecaploid accessions found in South America resemble each other and apparently differ from the North American duodecaploid B. arizonicus as regards chromosome size and nuclear DNA content (40.00 and 40.50 pg vs. 27.59 pg). These observations suggest that the South American duodecaploids represent a separate evolutionary lineage of the B. subgenus Ceratochloa, unrecognized heretofore.
authors.affiliation: Cytogenetics Group in the Department of Plant Breeding and Seed Science, University of Agriculture in Kraków, Cracow Poland.
authors.forename: Joanna
authors.initials: J
authors.lastname: Klos
authors.forename: Elwira
authors.initials: E
authors.lastname: Sliwinska
authors.forename: Adam
authors.initials: A
authors.lastname: Kula
authors.forename: Hieronim
authors.initials: H
authors.lastname: Golczyk
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Grabowska-Joachimiak
authors.forename: Tomasz
authors.initials: T
authors.lastname: Ilnicki
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Szostek
authors.forename: Alan
authors.initials: A
authors.lastname: Stewart
authors.forename: Andrzej J
authors.initials: AJ
authors.lastname: Joachimiak