All taxa contain the E genome, with or without additional genomes. Additional genomes known to be in some of its species are the St genome of Pseudoroegneria, the P genome of Agropyron, and possibly the L genome of Festucopsis. The use of E, rather than J, for the genome present in all members of the genus follows the recommendations of Wang et al. (1996) and maintains consistency with earlier usage by wheat breeders. These authors used the same symbol for the genome present in Lophopyrum, regarding the similarity between the two sufficient to use a single symbol, although the variant involved can be indicated by a superscript.
Perennnial plants with solitary spikelets. Glumes and lemmas coriaceous, usually glabrous, and with truncate to acute tips. Pedicels absent.
Plants perennial, sometimes rhizomatous, not stoloniferous. Culms 70-225 cm tall, lowest internode 1.3-3.5 mm thick.
Leaves 1-8 mm wide, flat or convolute, sometimes only the margins convolute, upper surface usually with prominent ribs.
Inflorescence spikelike, stiff; rachis usually tough, disarticulating in T. junceum, terminating in a spikelet, cross section trapezoidal, lowest internode longer than the middle internodes; middle internodes 8-22 mm long; initial disarticulation usually below the glumes, sometimes in the rachis, sometimes below the florets.
Spikelets solitary, tangential to the rachis, usually glabrous, not pedicellate, lowest spikelet shorter to subequal to the adjacent internode, sometimes much shorter, middle spikelets longer than the adjacent internode, usually less than twice as long.
Glumes 5.5-17 mm long, 0.9-2.3 mm wide, coriaceous, from half the length of the adjacent lemmas to almost as long as them, usually glabrous, midvein sometimes with a few, squat teeth on the distal portion, almost flat over the midvein or strongly keeled distally, margins scarious, particularly distally, tip truncate, obtuse, or acute, usually muticous, sometimes mucronate, occasionally shortly awned.
Lemmas usually glabrous and smooth, occasionally both the glumes and the lemmas evenly hairy all over the surface. lemmas usually rounded over the midvein except keeled distally, tips truncate to acute, occasionally awned, awn to 3 mm. Paleas not winged, tapering in the distal quarter. Lodicules fimbriate. Anthers 4-11 mm long.
Thinopyrum includes 15-25 taxa, but not all the taxa have valid combinations in the genus. For a listing go to http://herbarium.usu.edu/triticeae/thinopyrum.htm
Native to Europe, western Asia, and southern Africa; a few species have become established in other parts of the world.
Thinopyrum is sometimes interpreted more narrowly than here. For instance, Ellesnog-Staam et al. (2001) include some of its species in Psammopyrum. In addition, some taxonomists also recognize Lophopyrum and Trichopyrum as distinct genera. If recognized, Trichophyrum includes only T. intermedium which differs from other species of Thinopyrum in combining the E and St genomes.
Thinopyrum junceum L.
There has been no taxonomic treatment of the group as a whole in which the type species were reviewed, nor one in which the author accepted the genus. Not surprisingly, there are some nomenclatural questions that can only be resolved by consulting potential and known type specimens. In addition, several new combinations are needed if the genus is to be circumscribed as here. A highly desirable development would be formal, illustrated taxonomic treatment with parallel descriptions and both dichotomous and polychotomous keys that reflect the treatment.
Jarvie, J.K. 1992. Taxonomy of Elytrigia sect. Caespitosae and sect. Junceae (Gramineae: Triticeae). Nordic J. Bot. 12:155-169.
Wang, R.R-C., R. von Bothmer, J. Dvorak, G. Fedak, I. Linde-Laursen, and M. Muramatsu. 1995. Genome symbols in the Triticeae (Poaceae). Pp. 29-34 in R.R-C. Wang, K.B. Jensen, and C. Jaussi, [Editors], Proc. Second International Triticeae Symposium. Forage and Range Laboratory, U.S.D.A.-A.R.S., Logan, Utah.