Previous studies have suggested that the H haplome in Elymus could originate from different diploid Hordeum species, however, which diploid species best represent the parental species remains unanswered. The focus of this study seeks to pinpoint the origin of the H genome in Elymus. Allopolyploid Elymus species that contain the StH genome were analyzed together with diploid Hordeum species and a broad sample of diploid genera in the tribe Triticeae using DMC1 sequences. Both parsimony and maximum likelihood analyses well separated the American Hordeum species, except Hordeum brachyantherum subsp. californicum, from the H genome of polyploid Elymus species. The Elymus H-genomic sequences were formed into different groups. Our data suggested that the American Horedeum species, except H. brachyantherum subsp. californicum, are not the H-genomic donor to the Elymus species. Hordeum brevisubulatum subsp. violaceum was the progenitor species to Elymus virescens, Elymus confusus, Elymus lanceolatus, Elymus wawawaiensis, and Elymus caninus. Furthermore, North American H. brachyantherum subsp. californicum was a progenitor of the H genome to Elymus hystrix and Elymus cordilleranus. The H genomes in Elymus canadensis, Elymus sibiricus, and Elymus multisetus were highly differentiated from the H genome in Hordeum and other Elymus species. The H genome in both North American and Eurasian Elymus species was contributed by different Hordeum species.

The phylogeny of diploid species in the genus Hordeum has been studied intensively. Although the origin of American polyploid species has been analyzed using multiple-copy internal transcribed spacer sequences, the origins of these species in Hordeum remain unclear. The objectives of our study were to elucidate the origins of American polyploid species and to explore phylogenetic relationships of these polyploids to diploid Hordeum and other diploid species in Triticeae using a single copy of a nuclear gene, disrupted meiotic cDNA1 (DMC1). DMC1 sequences from nine Hordeum polyploid species were analyzed. Sequence comparisons revealed that one copy of sequences from polyploid species Hordeum fuegianum, Hordeum jubatum, and Hordeum tetraploidum showed a 82 bp miniature inverted-repeat terminal element (MITE) (Stowaway) insertion, which was also detected in the Triticeae diploid species Australopyrum species (W genome) and Taeniatherum caput-medusae (Ta genome). Maximum parsimony and Bayesian analysis suggested that diploid Hordeum brachyantherum subsp. californicum is one ancestor of polyploids Hordeum arizonicum, H. brachyantherum subsp. brachyantherum, Hordeum depressum, and Hordeum procerum. The other ancestor of tetraploid H. depressum is probably Hordeum euclaston. Hordeum cordobense was suggested to be one of the genome donors to hexaploid H. procerum. The diploid Hordeum flexuosum and tetraploid H. tetraploidum were suggested as the parents to hexaploid species Hordeum parodii. The result is that one sequence from each of three Hordeum tetrapolyploids, including H. fuegianum, H. jubatum, and H. tetraploidum, and one from Hordeum hexaploid H. arizonicum fall outside the Hordeum clade of the DMC1 phylogenetic tree, therefore representing another example of complex evolutionary history. Our data may shed light on future phylogenetic studies in Triticeae, especially for the polyploids, by broadening the scope of investigations through sampling more genome types in Poaceae, not only from the tribe Triticeae. Résumé : La phylogénie d'espèces diploïdes, au sein du genre Hordeum, a été étudiée intensivement. Bien que l'origine des espèces polyploïdes d'Amérique ait été analysée en utilisant les séquences de l'espaceur interne transcrit en copies multiples, les origines des espèces d' Hordeum demeurent floues. Cette étude a pour objectifs d'élucider les origines d'espèces polyploïdes d'Amérique et d'explorer les relations phylogénétiques entre ces polyploïdes les Hordeum diploïdes ainsi que d'autres espèces diploïdes chez les Triticeae, en utilisant un gène nucléaire en simple copie, le cADN1 méiotique perturbé (C1MP). Les séquences C1MP provenant de neuf espèces d'Hordeum polyploïdes ont été analysées. Les comparaisons de séquence ont révélé qu'une copie des séquences provenant des espèces polyploïdes H. fuegianum, H. jubatum, et H. tetraploidum montrait l'insertion d'un élément terminal inversé-répété miniature (ETMI) (stowaway) de 82 pb, lequel a aussi été détecté chez les espèces de Triticeae diploïdes Australopy...