Morphology, Cytology, and Fertility of F1 and Induced‐amphiploid Hybrids of Elymus canadensis — Agropyron subsecundum1

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Abstract
Octoploid (2n=56) amphiploids of Elymus canadensis L. × Agropyron subsecundum (Link.) Hitchc. were obtained by treating sterile tetraploid (2n=28) F1 hybrids with colchicine. Chromosome doubling initially restored fertility but drastically reduced vegetative vigor. Dry matter yields of the amphiploids in the C2 to C5 generations were about 50% of those of the Fl's. The range in chromosome number changed from 2n=54 to 58 in the C1 to 2n=27 to 59 in the C5 generation, while the population means decreased from 2n=55.9 to 2n=53.8. Meiotic irregularities tended to increase in each succeeding amphiploid generation. Fertility declined from 2.36 seeds per spikelet in the Co generation to 0.78, 0.58, 0.50, 0.37, and 0.22 in the C1 to C5 generations, respectively. Amphiploid sterility was attributed to heterogenetic pairing between the closely related E. canadensis and A. subsecundum chromosomes. Chances of synthesizing a fertile, cytologically stable octoploid species from E. canadensis × A. subsecundum amphiploids, or from amphiploids with a similar genome constitution, are remote.