Species relationships in the Hordeum murinum aggregate viewed from chloroplast DNA restriction fragment patterns

Three annual widespread species of Hordeum were investigated by the fragment pattern method on their chloroplast (cp) DNA. The species were H. glaucum, H. leporinum and H. murinum; H. vulgare was surveyed for comparison. Twelve restriction enzymes were used, nine recognizing 6 bp, one 5 bp and two 4 bp, thus, randomly surveyed, a total of 2,113 bp or 1.6% of the cp genome. Differences in patterns were found in three enzymes, HindIII, CfoI and MspI. CfoI characterizes H. glaucum from the other two species. HindIII and MspI revealed polymorphisms within species. These results confirm previous numerical taxonomic relationships among these three closely related species. Furthermore, cpDNA polymorphism in Hordeum is discussed in view of earlier reports on cpDNA polymorphism in H. vulgare. The taxonomic implications of cpDNA polymorphism are discussed after reviewing several articles using the fragment pattern method on cpDNA. The importance of using material from several populations representative of a species is stressed.