Genome constitution of Elymus tangutorum （Poaceae： Triticeae）inferred from meiotic pairing behavior and genomic in situ hybridization

Elymus tangutorum （Nevski） Hand.-Mazz （2n = 6x = 42） is a perennial species in the tribe Triticeae, which distributes in Nepal and north and northwest China. However, the genome constitution of E. tangutorum is controversial and its taxonomic status is not clear. Hybridizations of E. tangutorum were carried out with E. wawawaiensis J. R. Carlson ＆ Barkworth （StH）, Roegnerio grondis Keng （.STY）, and E. dohuricus Turcz. ex Griseb. （.StYH）. Meiotic pairing in the hybrids E. tangutorum × E. wawawaiensis （StH）, E. tongutorurn × R. grandis （STY）, and E. tangutorurn × E. dahuricus （StYli） averaged 10.48, 11.12, and 20.92 bivalents per cell, respectively. The results suggested that E. tangutorum is an allohexaploid and contains the StYli genomes. Results of genomic in situ hybridization analysis strongly supported the chromosome pairing data. Therefore, E. tangutorum should be treated as Compeiostochys dahurica var. tangutorum （Nevski） B. R. Baum, J. L. Yang ＆ C. Yen. Intergenomic rearrangements of E. tangutorum may be affected by environmental factors.