13.10 PSEUDOROEGNERIA (Nevski) Á. Löve

Jack R. Carlson

Plants perennial; usually cespitose, sometimes rhizomatous. Culms 30–100 cm, usually erect, sometimes decumbent or geniculate. Leaves evenly distributed; sheaths open; auricles well developed; ligules membranous; blades flat to loosely involute. Inflorescences terminal spikes, erect, with 1 spikelet per node; internodes (7)10–20(28) mm at midlength, lower internodes often longer than those at midlength. Spikelets (8)12–25 mm, 1.1–1.5(2) times the length of the internodes, usually appressed, sometimes slightly divergent, with 4–9 florets; disarticulation above the glumes and below the florets. Glumes unequal, from shorter to slightly longer than the lowest lemma in the spikelets, lanceolate to oblanceolate, (3)4–5(7)-veined, usually acute to obtuse, occasionally truncate, narrowing beyond midlength, veins prominent; lemmas inconspicuously 5-veined, unawned or terminally awned, awns straight to strongly bent and divergent; anthers 4–8 mm. x = 7. Haplome St. Name from the Greek pseudo, ‘false’, and the genus Roegneria, an Asian taxon often included in Elymus.

Pseudoroegneria includes 15–20 species, one of which is North American and the remainder either Eurasian or Asian. All species currently included in the genus are obligate outcrossers, and almost all are diploids or autotetraploids (Jensen et al. 1992) containing the St haplome (designation by the International Triticeae Consortium). This genome is the most widely distributed in the Triticeae, being found in all species of Elymus sensu lato as well as some species of Thinopyrum.

The limits of Pseudoroegneria are not well established, whether it is treated as a genus, as here, or included in Elytrigia (Tsvelev 1976) or Elymus (Melderis 1980). Two species that were originally included have been transferred to Douglasdeweya C. Yen, J.L. Yang & B.R. Baum (Chen et al. 2005), because specimens grown at agricultural experiment stations were found to be StP allotetraploids (Jensen et al. 1992; Wang et al. 1986; Chen et al. 2005).

There are also questions concerning the delimitation of species in Pseudoroegneria. For instance, Jensen et al. (1995) suggested that P. spicata, P. strigosa (M.-Bieb.) Á. Löve, P. geniculata (Trin.) Á. Löve, P. elytrigioides (C. Yen & J.L. Yang) Bao-Rong Lu, and Roegneria glaberrima Keng & S.L. Chen should be considered members of a single transberingian species complex. They presented cytological, but not morphological, analyses supporting their conclusion.

SELECTED REFERENCES Assadi, M. and H. Runemark. 1995. Hybridization, genomic constitution and generic delimitation in Elymus s.l. (Poaceae, Triticeae). Pl. Syst. Evol. 194:189–205; Dewey, D.R. 1984. The genomic system of classification as a guide to intergeneric hybridization in the perennial Triticeae. Pp. 209–279 in J.P. Gustafson (ed.). Gene Manipulation in Plant Improvement. Plenum Press, New York, New York, U.S.A. 668 pp.; Daubenmire, R.F. 1939. The taxonomy and ecology of Agropyron spicatum and A. inerme. Bull. Torrey Bot. Club 66:327–329; Daubenmire, R.F. 1960. An experimental study of variation in the Agropyron spicatum–A. inerme complex. Bot. Gaz. 122:104–108; Jensen, K.B, S.L. Hatch, and J. Wipff. 1992. Cytogenetics and morphology of Pseudoroegneria deweyi (Poaceae: Triticeae), a new species from the Soviet Union. Canad. J. Bot. 70:900–909; Jensen, K.B., M. Curto, and K.H. Asay. 1995. Cytogenetics of Eurasian bluebunch wheatgrass and their relationship to North American bluebunch and thickspike wheatgrasses. Crop Sci. 35:1157–1162; Melderis, A. 1980. Elymus. Pp. 192–198 in T.G. Tutin, V.H. Heywood, N.A. Burges, D.M. Moore, D.H. Valentine, S.M. Walters. and D.A. Webb (eds.). Flora Europaea, vol. 5. Cambridge University Press, Cambridge, England. 452 pp.; Tsvelev, N.N. 1976. Zlaki SSSR. Nauka, Leningrad [St. Petersburg], Russia. 788 pp.; Voss, E.G. 1972. Michigan Flora: A Guide to the Identification and Occurrence of the Native and Naturalized Seed-Plants of the State, part 1. University of Michigan, Ann Arbor, Michigan, U.S.A. 488 pp.; Wang, R.R-C., D.R. Dewey, and C. Hsiao. 1986. Genome analysis of the tetraploid Pseudoroegneria tauri. Crop Sci. 26:723–727; Yen, C., J.-L. Yang, and B.R. Baum. 2005. Douglasdeweya: A new genus, with a new species and a new combination (Triticeae: Poaceae). Canad. J. Bot. 83:413–419.

1. Pseudoroegneria spicata (Pursh) Á. Löve

Bluebunch Wheatgrass

Plants loosely cespitose, sometimes rhizomatous. Culms 30–100 cm tall, 0.5–2 mm thick, sometimes glaucous. Ligules truncate, 0.1–0.4 mm on the lower leaves, 0.2–0.4 mm on the upper leaves; blades 2–6 mm wide, involute when dry, flag leaf blades strongly divergent when dry, abaxial surfaces smooth, glabrous, adaxial surfaces scabrous or hirsute. Spikes 8–15 cm long, 3–8(10) mm wide excluding the awns; middle internodes 7–20(25) mm, glabrous, scabrous on the angles. Spikelets 8–22(25) mm, with 4–9 florets. Glumes 6–13 mm long, 0.9–2.2 mm wide, about 1/2 the length of the spikelets, glabrous, sometimes scabrous over the veins, acute; lemmas 9–14 mm, unawned or with a terminal, strongly divergent awn, awns to 25 mm. 2n = 14, 28.

Pseudoroegneria spicata is primarily a western North American species, extending from the east side of the coastal mountains to the western edge of the Great Plains, and from the Arctic Ocean to northern Mexico. It was also collected by Farwell in Keenewaw County, Michigan in 1895 (Voss 1972). It grows on medium-textured soils in arid and semiarid steppe, shrub-steppe, and open woodland communities, and was one of the dominant species in grassland communities of the Columbia and Snake river plains (Daubenmire 1939, 1960). It is still an important forage plant in the northern portion of the Intermountain region. Several cultivars have been developed.

Rhizomatous plants are favored in relatively moist habitats, and cespitose plants in dry habitats (Daubenmire 1960). Daubenmire noted that rhizomatous plants produce few inflorescences and, possibly for this reason, are collected less frequently than cespitose plants. Daubenmire also found that awn length varies continuously within plants grown from seed. He concluded that the ability to produce rhizomes and unawned plants is heritable, that the two characters are not linked, and that the form which becomes dominant at a local site is determined by environmental conditions.

The unawned phase tends to be more restricted in its distribution than the awned phase, being dominant in the native grasslands of southern British Columbia, eastern Washington, northern Idaho, and northern and eastern Oregon; the awned phase is found throughout the range of the species. Many populations include awned and unawned plants, as well as some that have poorly developed awns on some lemmas. Awned autotetraploid populations grow in mesic grassland and woodland communities of the hills and mountains of southern British Columbia and eastern Washington.

Based on informal observations, plant breeders working with Pseudoroegneria spicata consider that awn presence is determined by a single major gene, and modified by some minor genes. The unawned condition is apparently dominant, as seed from crosses of heterozygotic, diploid, unawned parents gives rise to around 50% awned offspring.

The above observations make it clear that the awned and unawned phases of Pseudoroegneria spicata are of little taxonomic significance, despite their evident morphological difference. If it is considered necessary to distinguish between them, the awned phase can be called Pseudoroegneria spicata (Pursh) Á. Löve forma spicata and the unawned phase P. spicata forma inermis (Scribn. & J.G. Sm.) Barkworth.

Plants with densely pubescent leaves are known from the east slope of the Cascade Mountains in Washington. Plants with nearly as densely pubescent leaves are found elsewhere in southern Washington and northeastern Oregon. Such pubescent plants may be called Pseudoroegneria spicata forma pubescens (Elmer) Barkworth.

Pseudoroegneria spicata used to be confused with Elymus wawawaiensis, from which it differs in its more widely spaced spikelets and wider, less stiff glumes. The two species are geographically sympatric, but P. spicata grows in medium- to fine-textured loess soils, and E. wawawaiensis in shallow, rocky soils. Pseudoroegneria spicata may also be confused with Elymus arizonicus, particularly with immature specimens of that species or specimens mounted so that they appear to have erect, rather than drooping, spikes. It differs in having shorter, truncate ligules and generally thicker culms than E. arizonicus, and in having a distribution that extends much further north.

Pseudoroegneria spicata has been suggested as one of the parents in numerous natural hybrids with species of Elymus in the Flora region. These hybrids are usually mostly sterile, but development of even a few viable seeds permits introgression to occur, as well as the formation of distinctive populations. It is often difficult to detect such hybrids, particularly if they involve the unawned form of Pseudoroegneria. The named hybrids are treated under ×Pseudelymus (p. ??). Others are discussed under the Elymus parent.