BLATTNER, FRANK R. Dept. of Taxonomy, IPK, D-06466 Gatersleben, Germany. - Tracing allopolyploid speciation in Hordeum.
The genus Hordeum L. occurs with about 32 species in temperate
climates mostly in Eurasia and the Americas. Four basic genomes were
described within Hordeum: 'I' in barley and the closely related
H. bulbosum, 'Y' in H. murinum, 'X' in H.
marinum, and 'H' in all other species of the genus. The latter
group contains several (tetra- and hexa-) polyploids. To reveal
species history the nrDNA ITS region of all Hordeum species was
PCR amplified, cloned, and several clones of each species were
sequenced. The analysis of the resulting sequences allowed in many
cases the reconstruction of the parental ancestors (or ancestor
groups) of allopolyploids and a distinction between putative auto- and
allopolyploid species. Phylogenetic analysis clusters 'I' and 'Y'
genomes and 'X' and 'H' genomes, respectively, and reveals a SW Asian
origin of the genus. A relatively fast radiation occurred in C Asia
and S America possibly due to the evolution of salt tolerance and/or
small seeds in a basal taxon of the X/H subgroup of the genus.
Key words: Hordeum, hybridization, internal transcribed spacer, phylogenetic analysis