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Leymus cinereus & L. salina
Illustrator Cindy Roché.
©Utah State University

Leymus racemosus, Leymus arenarius, & Leymus mollis
Illustrator Cindy Roché.
©Utah State University

Distribution of species, compiled from regional floras

Genomic constitution

Two versions of the N genome which is derived from the Psathyrostachys. It is not apparent why they should be recognized as two separate genera but molecular markers say there is a substantial difference between the two genomes in Leymus and between them and the version in Psathyrostachys.

Distinguishing features

Plants perennial, usually rhizomatous, growing in alkaline or saline soils. Spikelets usually 2 or more per nodes, sometimes only one in inland species. Glumes membranous and lanceolate or horn-like  to subulate.  Glumes and lemmas muticous or shortly (to 7 mm) awned.

Description

Plants perennial, usually rhizomatous, sometimes forming clumps. Culms 10-350 cm tall.

Leaf blades 1-20 mm wide, usually involute, usally prominently ribbed on the upper surface.

Inflorescence usually spikelike, sometimes paniculate, 1.5-35 cm long, rachis tough, terminating in a ; middle internodes 3.5-15 mm long; disarticulation below the florets.

Spikelets 1-8 per node, tangential to the rachis when solitary, 8-35 mm long, with 2-12 florets, middle spikelets half to almost 4 times as long as the adjacent internodes.

Glumes usually equal to subequal, sometimes highly reduced or absent, 0-30 mm long, sometimes almost as long as the adjacent lemmas, lanceolate, membranous, and flexible or lanceolate-subulate, tapering from below midlength, and stiff, 0-5(7) veined, keels straight, tips unawned or with an awn no more than 4 mm long. Lemmas 7-25 mm long, acute, unawned or with straight awns to 7 mm long. Paleas >>>. Lodicules??. Anthers 2.5-10 mm.

Size

About 50, most of which are in Central Asia.

Distribution

Cool and temperate regions of Eurasia and the Americas, generally in alkaline or saline areas, including shorelines.

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Alternative interpretations

Leymus is now accepted by most taxonomists. The only question concerns whether it should include some of the species that have no glumes. In the Flora of China, these are included in Hystrix but, in the Flora of North America, the type of Hystrix is included in Elymus. It appears that loss of glumes has occurred within different lineages in the Triticeae. The taxoomic implications of this statement have not yet been resolved.

Type species

Leymus arenarius Hochst.

Known problems

The relationship of Leymus triticoides to Leymus simplex, Leymus salina, Leymus ambiguus, and Leymus multicaulis  needs further study.

References

Ahokas, H. and B. Fredskild. 1991. Coexistence and hybridization of Leymus mollis and L. arenarius in Greenland, and demarcation of the species by endospermal prolamins, leymins. Nordic J. Botany 11: 385-392.

Anamthawat-Jonsson, K., B.Th. Bragason, S.K. Bodvarsdottir, and R.M. Koebner. 1999.  Molecular variation in Leymus species and populations.  Molecular Ecology 8:309-315. 

Barkworth, M.E. and R.J. Atkins. 1984. Leymus Hochst. (Gramineae: Triticeae) in North America: taxonomy and distribution. American Journal of Botany. 71:609-625.

Dubcovsky, J., A.R. Schlatter, and M. Echaide. 1997. Genome analysis of South American Elymus (Triticeae) and Leymus (Triticeae) species based on variation in repeated nucleotide sequences. Genome 40:505-520. [Elymus erianthus and E. mendocinus transferred to Leymus; other South American species found to be StH or StHH]

Hole, D.J., K.B. Jensen, R.R.-C. Wang, and S.M. Clawson. 1999. Genome analysis of Leymus flavescens : Chromosome pairing and Molecular Genomic Markers (Poaceae: Triticeae). International  Journal of Plant Science 160: 371-376.

Jensen, KB., and Wang, RRC. 1997. Cytological and molecular evidence for transferring Elymus coreanus from the genus Elymus to Leymus and molecular evidence for Elymus californicus (Poaceae: Triticeae). International Journal of Plant Sciences, 158: 872-877.

Sun, G., Yen, C., and Yang, JL. 1994. The genome constitution of Leymus aemulis (Poaceae). Hereditas. 121: 191-195.

Wang, RRC., and C. Hsiao. 1984. Morphology and cytology of interspecific hybrids of Leymus mollis . Journal of Heredity 75:488-492.

Wang, RR-C., and K.B. Jensen. 1994. Absence of the J genome in Leymus species (Poaceae: Triticeae): Evidence from DNA hybridization and meiotic pairing. Genome 37: 231-235.

Wu, X., Larson, SR., Hu, Z., Palazzo, AJ., Jones, TA., Wang, RR-C., Jensen, KB., Chatterton , NJ . 2003. Molecular genetic linkage maps for allotetraploid Leymus wildryes (Gramineae: Triticeae). Genome 46: 627-646.

Zhang, H.B. and J. Dvorak. 1990. The genome origin of tetraploid species of Leymus (Poaceae: Triticeae) inferred from variation in repeated nucleotide sequences. Amer. J. Bot. 78: 871-884.