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Intermediate Wheatgrasses of Iran¹

Geographic distribution, morphology, cytology, and fertility were studied in 247 collections of the intermediate wheatgrass complex (Agropyron intermedium (Host) Beauv., A. trichophorum (Link) Richt., and A. pulcherrimum Grossh.) collected in Iran and grown at Logan, Utah. This group of grasses is the most widespread Agropyron complex in Iran, occurring at altitudes of 500 to 2,700 m in the Alborz and Zagros mountain ranges and in semiarid plateau regions north of 30° N Lat. A 2,735-plant population was extremely diverse in vegetative and spike characteristics. Plant breeders will find ample variation in these collections for significant improvement in forage and seed production. Of 234 plants, 93% had a chromosome number of 2n=42, and the remainder were 2n=41, 43, 45, and 52. Chromosome pairing at metaphase I averaged 0.60^I, 20.19^II, 0.05^III, 0.20^IV, 0.002^V, and 0.008^VI per cell in 1,926 cells. Pairing was in harmony with the hypothesis that intermediate wheat grasses are segmental autoallohexaploids. Open-pollination fertility of 247 plants ranged from 0.0 to 72.8 seeds per spike and averaged 35.5. Self-fertility of the same plants ranged from 0.0 to 44.4 seeds per spike and averaged 5.7. Occasional plants were highly self-fertile, a condition previously unknown in these grasses. The spike characteristics that separate A. intermedium, A. trichophorum, and A. pulcherrimum taxonomically, i.e., pubescent vs. glabrous lemmas and awns vs. awnlessness, segregated in the population as if they were simply inherited traits. The three taxa cannot be separated on the basis of geographic distribution, ecological adaptation, cytological characteristics, or reproductive behavior. Consequently, all should be treated as a single species, A. intermedium.

Key Words: Agropyron intermedium • Agropyron trichophorum • Agropyron pulcherrimum • Taxonomy • Plant-exploration • Cytogenetics

² Research geneticist, ARS-USDA, Logan, UT 84322.

Received for publication April 15, 1977.