Molecular phylogeny of the genus Hordeum and origins of Hordeum polyploidy species

Abstract

The phylogeny of the diploid species in the genus Hordeum has been studied intensively, however, there has been incongruences between nuclear and chloroplast datasets. In addition, the origins of polyploid species in Hordeum remain unclear. The aims of the present study are to: 1) Investigate the phylogeny of Hordeum diploid species. 2) Investigate the origins of Hordeum polyploids, with combined genetic information from both chloroplast and nuclear datasets. Thirty two Hordeum species from eighty accessions were used in this study. In total 214 sequences from three single copy nuclear genes and two chloroplast regions were obtained. Both nuclear and chloroplast phylogenies of Hordeum diploids are supported by previous studies, and our study suggests the major incongruence between them could be explained by incomplete lineage sorting. For polyploids, our study confirms H. brachyantherum subsp. californicum is the parent of H. brachyantherum subsp. brachyantherum and H. depressum . The present study does not favor previous results that H. roshevitzii is the possible parent of H. tetraploidum and H. fuegianum . Instead, this study suggests H. brevisubulatum is the possible genome donor to tetraploids H. brachyantherum subsp. brachyantherum, H. tetraploidum, H. fuegianum and hexaploids H. lechleri and H. procerum . The present study also suggests the other genome donor of H. tetraploidum and H. fuegianum might come from H. patagonicum species. The diploid H. pusillum is further confirmed as the maternal parent of H. arizonicum in the present study. Previous suggestion on H. tetraploidum as the possible tetraploid genome donor of H. parodii and H. procerum is supported by our study. In addition, the study also suggests H. flexuosum is one possible genome donor of hexaploid H. parodii .