Taxonomic Notes: Hordeum marinum Huds. is a tertiary wild relative of Barley, H. vulgare L. (USDA, ARS, National Genetic Resources Program ). Differs from Hordeum leporinum and Hordeum glaucum in that the junction of the with line drawing: Background and Aims Hordeum marinum. is a species complex that includes the diploid subspecies marinum and both diploid and tetraploid.
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However, only three marinum accessions were used in this study; more must be examined to support the separation of subspecies marinum into two or more geographically differentiated cytotypes. Published online Nov 5. The considerable genome size variation of Hordeum species Poaceae is linked to phylogeny, life form, ecology, and speciation rates.
It is reasonable to assume that this could be due to the amplification of pre-existing interstitial 5SrDNA sequences in an ancient form present in the Iberian Peninsula after the geographical isolation of marinum populations in glacial refuges during the Pleistocene Jakob et al.
Cytogenetic and Genome Research. The relationships within this group of waterlogging-tolerant barleys have remained unclear. It may also be that related forms of the diploid accessions analysed were parentals and underwent significant genomic and chromosomal changes during the generations coming soon after polyploidization.
AAG 5which produced the clearest pattern of signals, was chosen as the diagnostic probe for identifying chromosomes and for analysing the physical mapping of the set of probes in multiple-target in situ experiments Fig. Identification of all chromosome arms and their involvement in meiotic homoeologous associations at metaphase I in 2 Hordeum vulgare L. However, in the tetraploids, which have more chromosomes of similar morphology and in situ pattern, it was very hard to identify individual chromosomes Fig.
In addition, as in diploid gussoneanuman interstitial site was found at a similar location on the long arm of a very submetacentric chromosome. An autopolyploid origin is supported by a number of cytogenetic studies, including the analysis of C-banded karyotypes and the meiotic behaviour of hybrids Bothmer et al.
Conclusions The tetraploid forms of gussoneanum appear to have come about through a cross between a diploid gussoneanum progenitor and a second, related—but unidentified—diploid ancestor.
Another major disagreement concerns the auto- or allopolyploid origin of the tetraploids. The authors thank Adrian Burton for linguistic assistance. It is noteworthy that no other diploid Hordeum species has a 5SrDNA locus on the long arm of its satellitized chromosomes de Bustos et al.
Progenitor-derivative relationships of Hordeum polyploids Poaceae, Triticeae inferred from sequences of TOPO6, a nuclear low-copy gene region.
Life Form – primary Therophyte annual land plant. New Hordeum – Triticum hybrids.
IUCN Red List of Threatened Species
One locus, which was sometimes resolved as a pair of two very close signals, was observed in the satellitized chromosome pair. Four probes were employed in FISH analyses: Utah State University; ACT 5 and ATC 5 returned very few signals, always of weak intensity, marinuk could not be used as diagnostic landmarks data not shown. This agrees with the monophyletic origin of this complex revealed by molecular studies of single nuclear genes and repeated DNA polymorphisms, which position all H.
Atlas c Atlas of north European vascular plants north of the Tropic of Cancer. It could be that independent mechanisms of amplification or reduction of the number of copies of each repeat sequence in different lineages occurred after they split from a common ancestor.
Although individual chromosome identification was very difficult with this probe, greater similarities were seen in the pattern of distribution of pAs1 among accessions BCC and GRA than between either of these accessions and accession GRA compare Fig.
The structure, amount and chromosomal localization of defined repeated DNA sequences in species of the genus Secale. Open in a separate window. Variation in highly repetitive DNA composition of heterochromatin in rye studied by fluorescence in situ hybridization.
In conclusion, this study reveals the origin of the polyploid forms of H. However, their clear morphological differences and the absence of gene flow between both diploid taxa have led several authors to regard them as separate species, i. The aim hordfum the present work was to identify chromosomal markers for characterizing the karyotypes of a representative sample of H.
The second pair with only one 5SrDNA locus only showed visible satellites in less condensed chromosomes Fig. Count of 10km squares in Ireland: January Mean Temperature Celsius: Their relationships, the rank of the taxa and the horseum of the polyploid forms remain points of debate.
Theoretical and Applied Genetics. For example, controversy exists regarding the polyphyletic or monophyletic origin of this species, in part due to conflicts between phylogenetic trees derived from narinum and nuclear sequences Blattner, ; Petersen et al. At the intraspecific level, the conserved distribution patterns of the 2 x gussoneanum accessions contrast with the diversity observed for the accessions of marinum.
Phylogenetic relationships within H.
Hordeum marinum | Online Atlas of the British and Irish Flora
The distribution, organization and evolution of two abundant and widespread repetitive DNA sequences in the genus Hordeum. The tetraploid forms of gussoneanum appear to have come about through a cross between a diploid gussoneanum progenitor and a second, related—but unidentified—diploid ancestor. Canadian Journal of Genetics and Cytology. This article has been cited by other articles in PMC. Note that signals observed with the ribosomal DNA probes clearly shown in Fig.
The distribution pattern of the set of repetitive DNA sequences, plus chromosome morphology, helped establish putative homologies among chromosomes assigned the same number in the subspecies of H.