Origin of the H genome in StH-genomic Elymus species based on the single-copy nuclear gene DMC1

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.

Amplified fragment length polymorphism in Elymus elymoides, Elymus multisetus, and other Elymus taxa

The geographic and phylogenetic significance of amplified fragment length polymorphism within and among 22 Elymus elymoides (Raf.) Swezey subsp. elymoides, 24 E. elymoides subsp. brevifolius (J.G. Sm.) Barkworth, and 13 Elymus multisetus (J.G. Sm.) Burtt-Davy squirreltail accessions was assessed relative to six other North American and three Eurasian Elymus taxa. Elymus elymoides and E. multisetus, comprising Elymus sect. Sitanion (Raf.) Á. Löve, were both monophyletic and closely related compared with other congeners. The monophyly of subsp. elymoides was also supported; subsp. brevifolius, however, was paraphyletic and separated into four genetically distinct groups. Estimates of nucleotide divergence among the five E. elymoides groups range from 0.0194 to 0.0288, with approximately 0.0329 differences per site between E. elymoides and E. multisetus. Corresponding estimates of nucleotide divergence range from 0.0243 to 0.0387 among North American taxa and from 0.0337 to 0.0455 between North American and Eurasian taxa. DNA polymorphism among E. elymoides accessions was correlated with geographic provenance and previously reported quantitative traits. Distinct genetic groups of E. elymoides generally correspond to different geographic regions, whereas divergent E. multisetus and E. elymoides accessions are sympatric. Thus, taxonomic ranks of E. multisetus and E. elymoides were supported and geographic groups within E. elymoides were distinguished.Key words: AFLP, Elymus, nucleotide diversity, squirreltail.