Physical mapping of repetitive DNA sequences and 5S and 18S–26S rDNA in five wild species of the genusHordeum

Abstract

The genetic relationships between several wild species and subspecies of the genus Hordeum were assessed using fluorescence in situ hybridization (FISH). Plant material included natural populations of wild barley growing in Spain of the annual species, H. marinum ssp. marinum (2n = 14) and gussoneanum (2n = 14), and H. murinum ssp. murinum (2n = 28), and leporinum (2n = 28) and the perennial species H. bulbosum (2n = 14) and H. secalinum (2n = 28), plus the South American perennial species H. chilense (2n = 14). FISH was used to locate the chromosomal sites of two rDNA multigene families 5S and 18S-26S (pTa71 and pTa794) and three repetitive DNA sequences (pSc119.2, pAs1 and pHch950) isolated from different species and genera. The seven chromosomes of the diploid species were readily distinguished by their external morphology and hybridization patterns to pTa71, pTa794, pSc119.2 and pAs1. These DNA probes were also useful for the identification of homologous chromosomes and in differentiating these from unidentified chromosomes in the tetraploid taxa. The use of the probe pHch950 permitted intergenomic differentiation in tetraploids and supports the diphyletic origin of H. murinum and H. secalinum. The in situ experiments yielded the following conclusions: (1) differences between the sub-species marinum and gussoneanum; (2) close relationships between the subspecies murinum and leporinum; and (3) major differences in physical mapping between H. bulbosum and the remaining taxa. The genomic and phylogenetic relationships between taxa, as inferred from the results, are discussed.

Phylogeny of two tetraploid Hordeum species, H. secalinum and H. capense inferred from physical mapping of 5S and 18S-25S rDNA

“…2). These results generally confirm the previous reports of rDNA patterns in diploid cytotypes of H. marinum (Bustos et al 1996, Taketa et al 1999a). The tetraploid cytotype of ssp.…”

“…In Hordeum, ribosomal DNA sites are excellent chromosome markers to study phylogenetic relationships of species (Bustos et al 1996, Taketa et al 1999a, 2001, 2005. Both classes of rDNA sites are known to evolve dynamically, and our interpretation assumes that all rDNA sites are generally conserved in these species.…”

Molecular phylogeny of the genus Hordeum using thioredoxin-like gene sequences

“…An alloploid origin of the tetraploid cytotype ssp. murinum 4x has been suggested by several cytological studies based on its C-banding pattern (LindeLaursen et al 1989) and rDNA sites (Bustos et al 1996, Taketa et al 1999b. Moreover, in situ hybridization analyses using repetitive DNA sequences as probes suggested that ssp.…”

Progress in phylogenetic analysis and a new infrageneric classification of the barley genus Hordeum (Poaceae: Triticeae)

“…These methods resulted in detailed karyograms of Hordeum species (Linde-Laursen et al 1992) and allowed the formulation of evolutionary hypotheses about species relationships (Linde-Laursen et al 1995 and references therein). I here shortly review advances in karyology with special emphasis on in situ hybridization methods introduced during the last two decades in Hordeum research (e.g., Leitch and Heslop-Harrison 1992, De Bustos et al 1996, Taketa et al 1999a, 2000b, and their special relevance to complement phylogenetic analyses in the genus.…”

“…FISH helps particularly to define the occurrence of rDNA tandem repeats on specific chromosomes, thus making (i) chromosome recognition much easier and (ii) allows also inference of the number of independent rDNA loci within a chromosome (e.g., Leitch and Heslop-Harrison 1992, De Bustos et al 1996, Taketa et al 2001. GISH data are quite helpful in the analysis of polyploids.…”