A Cytogenetic Basis for Transferring Russian Wildrye from Elymus to Psathyrostachys 1

Russian wildrye, Psathyrostachys juncea (Fisch.) Nevski, is a native grass of the Asian interior, but it has become in important range grass in western North America where it is known as Elymus junceus Fsisch. The purposes of this investigation were 1) to determine the genome relationships between Russian wildrye and Psathyrostachys fragilis (Boiss.) Nevski, and 2) to determine the appropriate taxonomic treatment of Russian wildrye. After several unsuccessful attempts, Russian wildrye was hybridized with P. fragilis in 1979. The parents and hybrids were diploid, 2n=14. More than half of the Metaphase‐I cells in the F 1 hybrids contained seven bivalents, demonstrating that the genomes of Russian wildrye and P. fragilis are closely homologous. The hybrids produced up to 5% stainable pollen, thus permitting introgression between the parent species. The cytogenetic data leave no doubt that Russian wildrye and P. fragilis are closely related and should be placed in the same genus, Psathyrostachys . The appropriate name for Russian wildrye is therefore P. juncea . European and Asian taxonomists are using this name, which should also be accepted in North America.