Species-specific in situ hybridization of Hordeum bulbosum chromosomes

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Abstract
BamHI-digested genomic DNA from three barley cultivars and four Hordeum bulbosum accessions was hybridized in Southern blots with two rye (Secale cereale) repetitive DNA sequences, clones pSc119.1 and pSc119.2. Both clones showed exclusive hybridization to H. bulbosum DNA. The pSc119.1 probe exhibited two strong and two weak bands on Southern blots of all four H. bulbosum accessions (two diploid and two autotetraploid). The two diploid H. bulbosum accessions exhibited a five-step ladder of DNA fragments with a periodicity of about 600 bp in Southern blots with pSc119.2. The band pattern of the two autotetraploids differed from the diploids as well as from each other. In in situ hybridizations with biotin-labelled probes, pSc119.1 hybridized predominantly to centromere regions of H. bulbosum chromosomes, with some interstitial sites, whereas pSc119.2 hybridized predominantly to a few telomeric sites. Three of the accessions exhibited one telomeric site on up to 6 chromosomes, while one accession had telomeric sites on up to 12 chromosomes, with one chromosome sometimes exhibiting hybridization at both telomeres. pSc119.2 hybridization to the satellite of H. bulbosum chromosome 6 revealed that two of the four accessions were heterozygous for the presence of DNA hybridization with this probe. No in situ hybridization was revealed on barley chromosomes with either probe. As discussed, these rye repetitive DNA probes could be used to detect the transfer of segments of H. bulbosum chromosomes, or from a number of other species, into barley.