DNA of 61 accessions representing 25 Hordeum species was tested for homology to a highly repeated 120-bp sequence from Secale cereale (rye). Homology to the probe (pSC119) was detected in dot blots of all species except H. vulgare (cultivated barley) and its related species, H. agriocrithon and H. spontaneum. Hybridization patterns of Southern blots of restriction fragments demonstrated both intraspecific and interspecific variation in the organization of complex units of DNA having homology to the probe. For eight species, digestion of the DNA with BamHI gave ladder patterns characteristic of tandem arrays of 120-bp repeat units. For EcoRI, HindIII, and SacI digests, the hybridization patterns appeared to be highly conserved in the section Hordeum, except those for H. bulbosum, which were unique. A further set of patterns for these three enzymes was common among the remaining species of the genus. Thus, DNA hybridization with pSC119 generally gave patterns consistent with the current taxonomy of Hordeum species, except that H. bulbosum and H. vulgare were not shown to be closely related.Key words: Hordeum, repeated DNA sequences, pSC119, species variation.
Highly repeated DNA families in the rat.