Cytogenetics of Agropyron ugamicum and Six of Its Interspecific Hybrids

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Abstract
Seven collections of A. ugamicum Drob., introduced into the USA from Central Asia in 1965, proved to be tetraploid, 2n = 28, and self-fertilizing. Hybrids were obtained between A. ugamicum and 6 other Agropyron spp. with known genome constitutions: North American A. spicatum (Pursh) Scribn. and Smith, 2n = 14, SS; Middle Eastern A. libanoticum Hack., 2n = 14, SS; Eurasian A. caninum (L.) Beauv., 2n = 28, SSHH; Eurasian A. mutabile Drob., 2n = 28, SSHH; North American A. trachycaulum (Link) Malte ex H. F. Lewis, 2n = 28, SSHH; and North American A. pringlei (Scribn. and Smith) Hitchc., 2n = 28, SSHH. Chromosome pairing in triploid hybrids showed that one of the 2 genomes of tetraploid A. ugamicum was partially homologous with the S genome of diploid A. spicatum and A. libanoticum, Pairing in the tetraploid hybrids showed that A. ugamicum had only the S genome in common with A. caninum, A. mutabile, A. trachycaulum and A. pringlei. The 2nd genome of A. ugamicum is designated as Y and the genome formula of A. uganmicum is SSYY. Species with S and Y genomes are East Asian grasses. The diploid source of the Y genome is unknown. If a YY diploid still exists, it probably occurs in Western Chain or Himalayan countries. All hybrids were totally sterile, which precludes introgression between A. ugamicum and the other 6 spp. Two hybrids, A. libanoticum .times. A. ugamicum and A. ugamicum .times. A. trachycaulum, were exceptionally vigorous and may have economic potential as forage grasses it fertility can be restored.