title: Ancestry of American polyploid Hordeum species with the I genome inferred from 5S and 18S-25S rDNA.
abstract: OBJECTIVE
  The genus Hordeum exists at three ploidy levels (2x, 4x and 6x) and presents excellent material for investigating the patterns of polyploid evolution in plants. Here the aim was to clarify the ancestry of American polyploid species with the I genome. *
  
  
  METHODS
  Chromosomal locations of 5S and 18S-25S ribosomal RNA genes were determined by fluorescence in situ hybridization (FISH). In both polyploid and diploid species, variation in 18S-25S rDNA repeated sequences was analysed by the RFLP technique. *
  
  
  RESULTS
  Six American tetraploid species were divided into two types that differed in the number of rDNA sites and RFLP profiles. Four hexaploid species were similar in number and location of both types of rDNA sites, but the RFLP profiles of 18S-25S rDNA revealed one species, H. arizonicum, with a different ancestry. *
  
  
  CONCLUSIONS
  Five American perennial tetraploid species appear to be alloploids having the genomes of an Asian diploid H. roshevitzii and an American diploid species. The North American annual tetraploid H. depressum is probably a segmental alloploid combining the two closely related genomes of American diploid species. A hexaploid species, H. arizonicum, involves a diploid species, H. pusillum, in its ancestry; both species share the annual growth habit and are distributed in North America. Polymorphisms of rDNA sites detected by FISH and RFLP analyses provide useful information to infer the phylogenetic relationships of I-genome Hordeum species because of their highly conserved nature during polyploid evolution.
authors.affiliation: Faculty of Agriculture, Kagawa University, Ikenobe, Miki, Kagawa 761-0795, Japan. staketa@ag.kagawa-u.ac.jp
authors.forename: Shin
authors.initials: S
authors.lastname: Taketa
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Ando
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Takeda
authors.forename: Masahiko
authors.initials: M
authors.lastname: Ichii
authors.forename: Roland
authors.initials: R
authors.lastname: von Bothmer
mesh_terms: D000569:Americas; D005075:Biological Evolution; D032461:Chromosomes, Plant; D004275:DNA, Ribosomal; D018745:Genome, Plant; D001467:Hordeum / Q000235:genetics*; D007621:Karyotyping; D012150:Polymorphism, Restriction Fragment Length; D011123:Polyploidy; D018749:RNA, Plant / Q000235:genetics*; D012335:RNA, Ribosomal / Q000235:genetics*
chemical_list: D004275:DNA, Ribosomal; D018749:RNA, Plant; D012335:RNA, Ribosomal