Synthetic Hybrids of Agropyron caespitosum X Agropyron spicatum, Agropyron caninum, and Agropyron yezoense

Agropyron caespitosum Koch, 2n = 14, produced 23 viable hybrid seeds in 80 hand-emasculated florets pollinated by A. spicatum (Pursh) Scribn. and Smith, 2n = 14. Unemasculated crosses of A. caespitosum x A. caninum (L.) Beauv., 2n = 28, and A. caespitosum x A. yezoense Honda, 2n = 28, yielded 124 and 4 viable hybrid seeds, respectively, with five maternal spikes per cross. Spike characteristics of the hybrids were generally intermediate between those of their parents. The A. caespitosum x A. caninum and A. caespitosum x A. yezoense hybrids were exceptionally robust, and their induced amphiploids may have possibilities in a breeding program. All parents were cytologically regular, and the tetraploid parents behaved as alloploids. The A. caespitosum x A. spicatum hybrids averaged 0.52I, 6.71II, and 0.02III at metaphase I. Chromosome pairing varied widely among A. caespitosum x A. caninum hybrids. Pairing was negligible in some plants, whereas others frequently formed seven closed bivalents. Genes for asynapsis may have influenced pairing in some plants. Four A. caespitosum x A. yezoense hybrids averaged 13.31I, 3.73II, and 0.08III at metaphase I, and most bivalents were open ended. The A. caespitosum x A. spicatum hybrids were completely sterile, but the other two hybrids produced an occasional seed. Asian A. caespitosum and North American A. spicatum contain closely homologous genomes. One of the two genomes of European A. caninum is closely related to the A. caespitosum genome, whereas a genome of Japanese A. yezoense is only remotely related to the A. caespitosum genome.