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Theoretical and Applied Genetics

, Volume 98, Issue 1, pp 1–9 | Cite as

Comparative physical mapping of the 5S and 18S-25S rDNA in nine wild Hordeum species and cytotypes

  • S. Taketa
  • G. E. Harrison
  • J. S. Heslop-Harrison

Absract

 The physical locations of the 5S and 18S-25S rDNA sequences were examined in nine wild Hordeum species and cytotypes by double-target in situ hybridization using digoxigenin-labelled 5S rDNA and biotin-labelled 18S-25S rDNA as probes. H. vulgare ssp. spontaneum (2n=2x=14; I-genome) had a similar composition of 5S and 18S-25S rDNA to cultivated barley (H. vulgare ssp. vulgare, I-genome), with two major 18S-25S rDNA sites and minor sites on four of the other five chromosomes; three chromosomes had 5S rDNA sites. The closely related H. bulbosum (2x; also I-genome) showed only one pair of 5S rDNA sites and one pair of 18S-25S rDNA sites on different chromosomes. Four wild diploid species, H. marinum (X-genome), H. glaucum and H. murinum (Y-genomes) and H. chilense (H-genome), differed in the number (2–3 pairs), location, and relative order of 5S and the one or two major 18S-25S rDNA sites, but no minor 18S-25S rDNA sites were observed. H. murinum 4x had three chromosome pairs carrying 5S rDNA, while the diploid had only a single pair. Two other tetraploid species, H. brachyantherum 4x and H. brevisubulatum 4x (both considered to have H-type genomes), had minor 18S-25S rDNA sites, as well as the major sites. Unusual double 5S rDNA sites – two sites on one chromosome arm separated by a short distance – were found in the American H-genome species, H. chilense and H. brachyantherum 4x. The results indicate that the species H. brachyantherum 4x and H. brevisubulatum 4x have a complex evolutionary history, probably involving the multiplication of minor rDNA sites (as in H. vulgare sensu lato), or the incorporation of both I and H types of genome. The rDNA markers are useful for an investigation of chromosome evolution and phylogeny.

Key words In situ hybridization Hordeum Karyotype evolution rDNA Barley 

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Copyright information

© Springer-Verlag Berlin Heidelberg 1999

Authors and Affiliations

  • S. Taketa
    • 1
  • G. E. Harrison
    • 2
  • J. S. Heslop-Harrison
    • 2
  1. 1.Research Institute for Bioresources, Okayama University, Chuo 2-20-1, Kurashiki 710, Japan Fax: +81 86 434 1249 E-mail: staketa@rib.okayama-u.ac.jpJP
  2. 2.Department of Cell Biology, John Innes Centre, Colney, Norwich NR4 7UH, UKGB

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