Thinopyrum is a genus of perennial grasses in the family Poaceae (tribe Triticeae, subfamily Pooideae), native to Eurasia and Africa. The roughly 16 recognised species are distributed across the Mediterranean basin, Europe, the Middle East, Caucasus, and parts of Africa, with several species naturalised in Australia, New Zealand, and North America.
Members of the genus are commonly called wheatgrasses on account of their seed heads, which closely resemble those of cultivated wheat (Triticum aestivum). Unlike wheat and most cereal crops, wheatgrasses are perennial: established stands regrow each season from persistent root systems and spreading rhizomes, making them ecologically valuable for soil stabilisation and potentially significant as sustainable grain crops.
The most widely studied species is Thinopyrum intermedium (intermediate wheatgrass), a sod-forming grass native to central and south-eastern Europe through Asia Minor that has been introduced across the western United States and Canada. Since the 1940s plant breeders have hybridised T. intermedium with common wheat to transfer disease-resistance traits, including resistance to leaf rust, powdery mildew, and wheat streak mosaic virus. T. elongatum (tall wheatgrass) similarly contributes leaf rust resistance genes to wheat breeding programmes. More recently, the Land Institute has developed domesticated selections of T. intermedium under the trademarked name "Kernza," a perennial grain crop whose seeds are richer in protein, calcium, iron, and dietary fibre than wheat and which builds rather than depletes soil organic matter.
Other notable members include T. junceum (sea couch), widespread around the Mediterranean and naturalised in Australia and New Zealand, and T. junceiforme (sand couch), characteristic of northern and central European coastal dunes.
Distribution
Thinopyrum species are native to Europe, the Mediterranean basin, the Middle East, the Caucasus, and parts of Africa. Several species have been introduced beyond their native range: T. intermedium is now widespread across the western United States and Canada, T. junceum has naturalised in Australia, New Zealand, Oregon, California, and the Falkland Islands, and T. junceiforme has established in Australia.
Ecology
Thinopyrum intermedium is adapted to open, well-drained habitats with 30–76 cm of annual rainfall, soils ranging from pH 5.6 to 8.4, and full sun exposure. As rhizomatous perennial grasses, Thinopyrum species contribute to soil stabilisation; their persistent root systems build soil organic matter rather than depleting it, in contrast to annual grain crops.
History
Wheatgrasses of the genus Thinopyrum have been the subject of crop-improvement efforts since the early twentieth century. T. intermedium was first introduced to the United States in 1907, with a more successful introduction from the Caucasus in 1932. Hybridisation with common wheat began in the 1940s. Systematic breeding for grain domestication started at the Rodale Research Center in 1983, and the work was taken up by the Land Institute, which trademarked the name "Kernza" for the resulting perennial grain. The genus name Thinopyrum was established to accommodate species previously classified under Agropyron and Elytrigia.
Taxonomy Notes
Species now placed in Thinopyrum were formerly classified in Agropyron (couch/wheatgrasses) and Elytrigia. Thinopyrum intermedium alone carries numerous historical synonyms including Agropyron intermedium, Agropyron glaucum, Elymus hispidus, and Elytrigia intermedia. GBIF places the genus in order Poales, family Poaceae, as an accepted genus. The broader Triticeae tribe also includes wheat (Triticum), barley (Hordeum), and rye (Secale), explaining the historical and ongoing hybridisation work.
