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Hybrids and Induced Amphiploids Involving Agropyron curvifolium, A. repens, and A. desertorum¹

Agropyron curvifolium Lange (2n=28) was hybridized with Agropyron repens (L.) Beauv. (2n=42). An amphiploid (2n=70) was produced by treatment of an F₁ (2n=35) with colchicine. The purposes of this study were to determine the mode of pollination and nature of polyploidy in A. curvifolium; to describe the morphology, cytology, and fertility of F₁ hybrids and a C₀ amphiploid of A. repens x A. curvifolium; and to describe a threespecies amphiploid hybrid involving A. repens, A. curvifolium, and A. desertorum (Fisch. ex Link) Schult.

Most A. curvifolium plants were highly self-sterile. Occasional quadrivalents in all A. curvifolium plants at metaphase I indicated that they were partial autoploids whose genome formula could be written as E₁E₁E₂E₂. Chromosome pairing in the F₁ hybrids averaged 14.82^I, 9.73^II, 0.20^III, and 0.03^IV. Most, if not all, pairing was the consequence of autosyndesis. The genome formula of the F₃ was designated as E₁E₂S₁S₂X.

Chromosome doubling of the F₂ hybrid increased plant height 20 to 25 cm. The amphiploid was meiotically irregular, averaging 6.02 univalents at metaphase I, 1.43 laggards at anaphase I, and 2.01 micronuclei per quartet. In spite of meiotic Irregularity, the amphiploid produced 90% stainable pollen. Some C₁ progeny were the result of crossing of the A. repens-A. curvifolium C₀ amphiploid (2n=70) to an A. repens-A. desertorum C₀ amphiploid (2n=70). The three-species amphiploid hybrids averaged 71% stainable pollen. The three-species amphiploid hybrids were the most vigorous plants in the study and they may warrant the attention of grass breeders.

Key Words: Interspecific hybridization • Quackgrass • Crested wheatgrass • Grass breeding • Polyploidy • Genome analysis

² Research geneticist, USDA-SEA-AR, Logan, UT 84322.

Received for publication January 28, 1980.