Characterization of Hordeum chilense chromosomes by C-banding and in situ hybridization using highly repeated DNA probes.

C-banding patterns of Hordeum chilense and of Triticum aestivum 'Chinese Spring' - H. chilense disomic addition lines were analyzed and compared with in situ hybridization patterns using a biotin-labeled highly repetitive Triticum tauschii DNA sequence, pAs1, and a wheat 18S-26S rDNA probe. All seven H. chilense chromosomes pairs and the added H. chilense chromosomes present in the addition lines were identified by their characteristic C-banding pattern. Chromosome morphology and banding patterns were similar to those of the corresponding chromosomes present in the parent H. chilense accession. A C-banded karyotype of the added H. chilense chromosomes was constructed and chromosome lengths, arm ratios, and relative length, as compared with chromosome 3B, were determined. The probe pAs1 was found to hybridize to specific areas on telomeres and interstitial sites along the chromosomes, allowing the identification of all seven pairs of the H. chilense chromosomes. Comparison of the patterns of distribution of the hybridization sites of clone pAs1 in the T. tauschii and H. chilense chromosomes was carried out by in situ hybridization on somatic metaphase chromosomes of the HchHchDD amphiploid. In situ hybridization using the 18S-26S rDNA probe confirmed that the H. chilense chromosomes 5Hch and 6Hch were carrying nucleolus organizer regions. The results are discussed on the basis of phylogenetic relationships between D and Hch genomes.