PHYLOGENETIC ANALYSIS OF THE GENUS HORDEUM USING REPETITIVE DNA-SEQUENCES

A set of six cloned barley (Hordeum vulgare) repetitive DNA sequences was used for the analysis of phylogenetic relationships among 31 speci es (46 taxa) of the genus Hordeum, using molecular hybridization techn iques. In situ hybridization experiments showed dispersed organization of the sequences over all chromosomes of H. vulgare and the wild barl ey species H. bulbosum, H. marinum and H. murinum. Southern blot hybri dization revealed different levels of polymorphism among barley specie s and the RFLP data were used to generate a phylogenetic tree for the genus Hordeum. Our data are in a good agreement with the classificatio n system which suggests the division of the genus into four major grou ps, containing the genomes I, X, Y, and H. However, our investigation also supports previous molecular studies of barley species where the u nique position of H. bulbosum has been pointed out. In our experiments , H. bulbosum generally had hybridization patterns different from thos e of H. vulgare, although both carry the I genome. Based on our result s we present a hypothesis concerning the possible origin and phylogeny of the polyploid barley species H. secalinum, H. depressum and the H. brachyantherum complex.