Elymus cylindricus (2n = 6x = 42) and E. breviaristatus (2n = 6x = 42) are distributed in grasslands and deserts of northern and north-western China. Their genomic constitution and taxonomic status are unclear. Elymus cylindricus was crossed with E. wawawaiensis J.R.Carlson & Barkworth (StH), Roegneria grandis Keng (StY) and Campeiostachys dahurica (Turcz. ex Griseb.) B.R.Baum, J.L.Yang & C.Yen var. dahurica (StYH). Meiotic pairing in the hybrids E. cylindricus 9 E. wawawaiensis (StH), E. cylindricus 9 R. grandis (StY) and E. cylindricus 9 C. dahurica var. dahurica (StYH) showed on average 10.00, 11.30 and 20.92 bivalents per cell, respectively. Elymus breviaristatus was crossed with C. dahurica var. dahurica (StYH) and E. cylindricus. Chromosome pairing in the hybrids of E. breviaristatus 9 C. dahurica var. dahurica and E. breviaristatus 9 E. cylindricus showed on average 19.60 and 19.27 bivalents, respectively. Genomic in situ hybridization (GISH) revealed the presence of St, Y and H genomes in E. cylindricus and E. breviaristatus. An intergenomic rearrangement was observed in E. cylindricus using GISH. Meiotic pairing data and GISH indicated that both E. cylindricus and E. breviaristatus are allohexaploids containing the StYH genomes. Elymus cylindricus and E. breviaristatus should be treated as Campeiostachys dahurica var. cylindrica and Campeiostachys breviaristata, respectively.

Elymus purpuraristatus and Roegneria calcicola are perennial species of wheatgrass in Triticeae (Poaceae), treated as members of different genera on the basis of morphological characteristics. However, their genomic constitution is still unknown and their taxonomic status remains disputed. To identify their genomic constitution, we performed chromosome pairing analysis, genomic in situ hybridization and phylogenetic analyses on E. purpuraristatus and R. calcicola. The meiotic pairing results for the artificial hybrids of E. wawawaiensis (StH) × E. purpuraristatus, E. purpuraristatus × Campeiostachys dahurica var. tangutorum (StYH) and R. calcicola × C. kamoji (StYH) suggested that E. purpuraristatus and R. calcicola are allohexaploid with the St, Y and H genomes. The genomic in situ hybridization results of E. purpuraristatus and R. calcicola confirmed that they possess two sets of the H genome and two sets of the StY genome. Phylogenetic analyses suggested that Acc1 and DMC1 sequences from E. purpuraristatus and R. calcicola grouped with the St genome clade, Y genome clade and H genome clade, respectively. In summary, cytological and phylogenetic results indicated that the genome formula of E. purpuraristatus and R. calcicola is StStYYHH. According to the genomic system of classification in Triticeae, E. purpuraristatus and R. calcicola should be classified in Campeiostachys as C. purpuraristata and C. calcicola, respectively.