Two new Tibetan species of Elymus (Poaceae: niticeae) and their genomic relationships

Two Elymus species, E. cacuminus (2n = 4x = 28) and E. retroflexus (2n = 2x = 28). native to western China are described as species new to science. In order to determine genomic constitutions of the two species, intergeneric and interspecific hybridizations were carried out between the two new species and Pseudoroegneria spicata (2n = 2x = 14, SS), and sixteen other Elymus species, fifteen tetraploids (2n = 4x = 28) and one hexaploid (2n = 6x = 42), containing the “SH”, “SY”, and “SYH” genomes. Chromosome pairing behaviour was studied in the two species and their hybrids. Generally low meiotic pairing was observed in the hybrids with S‐ and SH‐genome species and high pairing in the hybrids with SY‐ and SYH‐genome species. It is concluded from this study that (i) the two new species are strict allotetraploid (2n = 4x = 28) and self‐pollinating taxa (inbreeders) in nature; (ii) they contain the “SY” genomes and; (iii) they have close genomic relationships with the SY‐genome Elymus species from the same or geographically adjacent areas.