Thinopyrum intermedium

The native range of intermediate wheatgrass extends from central and southeastern Europe to Asia Minor. Although it was first brought to the United States in 1907, the first successful introduction was from the Caucasus region in 1932.[8] The plant can now be found growing wild throughout the Western United States and Western Canada.[6][9]

Thinopyrum intermedium is best adapted to:[6]

• Regions with annual rainfall between 12 and 30 inches
• Soil with a pH between 5.6 and 8.4
• Locations with full exposure to the sun
• A wide range of soils but with a minimum depth of 16 inches
• Locations where the minimum temperature exceeds -38 °F

Forage

Thinopyrum intermedium is among the most productive forage species for the western United States. Because it heads relatively late, it can be grown effectively in mixture with alfalfa to increase its productivity, longevity, and forage quality. It regrows slowly after grazing or cutting, making it best suited to management with a single harvest per year.[10] If multiple harvests are needed per year, other species will be more productive. If managed well, stands can persist for up to 50 years.

Habitat

Habitat for wildlife - intermediate wheatgrass can be an excellent food source for grazing and browsing animals. Left unharvested, the vegetation is a good nesting habitat for some birds and waterfowl. Generally, it is not an invasive plant and coexists well with native plant species.

Soil management

Erosion control and land rehabilitation are additional uses for this plant. It establishes quickly to form a protective mat of roots and rhizomes, even when planted on soils degraded by earth moving or mining. Within five years, stands have produced up to 7000 pounds of the dry root mass per acre in the top 8  inches of soil.[10] Heavy root production holds the soil in place and restores its natural fertility by increasing the soil carbon.

Grain

Thinopyrum intermedium is a perennial grain crop. In 1983, the Rodale Research Center evaluated close to 100 species of perennial grasses to identify those with good potential for development into perennial grain crops. Intermediate wheatgrass was selected as the most promising species based on flavor, ease of threshing, large seed size, resistance to shattering, lodging resistance, ease of harvest, and perennial growth.[11] Intermediate wheatgrass is nutritionally similar to wheat, and the grain can be ground into flour and used for food products, including muffins, tortillas, pancakes, cookies, crackers, and bread. Some products have been marketed under the trade name Kernza.[12]

Although the primary use of Thinopyrum intermedium is as a forage, seed production is essential because farmers and ranchers continue to establish new stands by planting the seed. In 1988 over 500 metric tons of seed were harvested in Saskatchewan alone, although more recently the harvest has fallen to less than 225 metric tons in that Canadian province.[13] Average seed yields are about 330 pounds per acre, but on-farm yields of up to 880 pounds per acre have been achieved. Seed is generally produced in rows spaced 30 to 36  inches apart. The wide row spacing (relative to grain crops like wheat) allows for sustained seed yields for five to ten years. Without spacing and occasional tillage between the rows, yields decline rapidly as the plant population becomes increasingly dense through rhizome spread. Despite this, Thinopyrum intermedium is still considered lesser than Wheat by some, as its seeds are comparatively tiny.[14]

Intermediate wheatgrass, Thinopyrum intermedium, has been widely hybridized with wheat in the effort to transfer traits such as disease resistance or perenniality.[15] Transferring leaf rust and powdery mildew resistance to wheat has been a special interest.[16] But, attempts to directly domesticate the species into a grain crop did not commence until workers at the Rodale Research Center began to evaluate collections in 1983.[17] In 1989, after assessing 300 collections, the workers selected the best twenty based on grain yield and seed quality. The selected collections were allowed to intermate, and 380 progeny were evaluated between 1991 and 1994. The best eleven plants, plus three from another evaluation, had intermated, causing a second cycle to begin. Seeds from the best plants in the second cycle were passed to scientists at The Land Institute, where the research has continued.

In 2001 and 2002, seed from the first and second breeding cycles of the Rodale Research Center was planted at The Land Institute. In the fall of 2003, 1000 individual plants were dug up and vegetatively propagated to obtain three clones of each plant. The 3000 resulting plants were randomly transplanted to the field on a three foot by three-foot grid. In this manner, genetic differences between plants were separated from environmental influences. In 2005, heads were harvested from every plant and threshed to remove the seeds. The seeds were both counted and weighed to determine the yield per seed head and weight per seed. The fifty plants with the highest yield and largest seed were selected to intermate in 2004.

In the fall of 2004, 4000 progeny were planted to establish the second cycle of breeding at The Land Institute. In 2008, these plants were harvested separately by using a power scythe and threshed in a combine. Again the best 50 plants were selected, this time based on yield per head, seed size, shortness, and free-threshing ability.

The selection methods described above have increased seed size and yield by about 10 to 18% per cycle.[18] But perhaps of greater importance has been the discovery of two Mendelian traits. The first is dwarfing, which results in stems about 30  cm shorter than wild-type plants and short, erect leaves (see photo). The second is a more subtle change in head shape which results in thick, non-brittle heads and slightly larger seeds (see picture). Both of these traits appear to be controlled by dominant genes.

The whole process mentioned above is called mass selection, which is breeding and selecting the best individuals to spawn the next generation. Mass breeding, however, is a process by which large quantities of genetically diverse individuals are made. Due to Thinopyrum intermedium's grass-like structures, some believe that it still needs to be domesticated as much as possible to resemble wheat.[19]

The fact that Thinopyrum intermedium is a perennial grass is important with regards to its use as a grain. The plant persists and can be harvested year after year, and its domestication would yield an additional three months of agriculture; its leaves are most active in the months in which common wheat is not active: July through September. Despite the promise, the yield per acre of Thinopyrum intermedium is 26% of the yield of traditional wheat. Because of this, some are putting effort into hybridizing wheat and Thinopyrum intermedium instead of attempting to domesticate Thinopyrum intermedium to a more acceptable yield.[20]

Attempts to hybridize Thinopyrum intermedium with wheat have also been done. This has some distinct advantages. First, there is wide evidence that hybridization of Thinopyrum intermedium with wheat is a method to confer fungal resistance to domestic wheat plants. However, which specific genes that protect against which specific fungus has not been as well studied. Thinopyum elongatum and Thinopyrum intermedium impart a total of four leaf rust resistance genes, while Thinopyrum intermedium confers two powdery mildew genes.[21] There's evidence that Thinopyrum intermedium also has resistance to wheat streak mosaic virus, the Aceria tosichella mite, Barley yellow dwarf, and others.[22] These conferred genes in wheat help increase yield and hardiness in times of environmental strain. Second, Thinopyrum intermedium also has genes that improve bread making when hybridized common wheat. While this may not seem like an important characteristic, better bread may mean more calories, feeding more people. In addition, bread that stays fresh longer may provide more opportunities for people to be adequately fed, and/or the bread can be transported to areas without much food access.[23]

The Land Institute has been working to develop viable wheat and Thinopyrum intermedium hybrid since 2001, and there have been several successful strains that shared 14 Thinopyrum intermedium chromosomes and 42 wheat chromosomes. These hybrids perform better regarding yield and resistance than either of their parents, but it cannot be widespread due to the changes of climate across the world. Also, perenniality is lost with these hybrids. This loss of perenniality is a common problem with hybridization attempts. All other desired characteristics are present in the hybrids - large seeds, good yields, etc. - except that the plants have taken on too many wheat characteristics: they are annual. However, crosses between durum wheat and Thinopyrum intermedium have resulted in hybrids that do exhibit perenniality in addition to other desired characteristics (increased vigor, hardiness in colder weather, good yield).[24] There are two general strategies for creating an alternate grain crop. One strategy is to domesticate Thinopyrum intermedium through mass breeding and selection to create a strain that mimics wheat's seed size and yield but retains Thinopyum Intermedium's natural resistances, hardiness, and perenniality. In other words, this strategy gives Thinopyrum intermedium more wheat-like characteristics. A second strategy is to hybridize wheat with Thinopyrum intermedium to create a strain of wheat that mimics Thinopyrum intermedium's resistance and perenniality but retains wheat's seed size and yield. In other words, this second strategy gives wheat more Thinopyrum intermedium-like characteristics. Researchers hope that these two strategies will progress and meet in the middle.[19]