Crested Wheatgrass

Appearance

''Agropyron cristatum'' is a densely tufted grass, with culms ranging from 30–50 cm high at maturity. Its sheaths are scabrous or the lowest ones pubescent. Its blades are up to 8 mm wide and scabrous to pubescent above. Its spikes are flat and range from 2–7 cm long, with spikelets ranging from 8–15 mm long, being 3–5-flowered, densely crowded, and spreading to ascending. Its glumes are 4–6 mm long, awn-tipped, and its lemmas are 6–8 mm long and either awnless or awn-tipped.

''Agropyron cristatum'' is known among other grasses and wheats for its relatively high granivory. Granivory, or granivores, describe the interaction between animals and seeds. ''Agropyron cristatum'''s high granivory indicates that animals feed on the seeds of the plant as their primary, or even exclusive, food source. Although this raises concerns about the plant's continued ability to reproduce if its seeds are all being consumed, the high granivory of this species does indicate that ''Agropyron cristatum'' is an important food source.

Habitat

''Agropyron cristatum'' is best adapted to dry rangeland conditions and is most frequently found in such circumstances. It prefers from 23 to 38 cm of precipitation per year, but can tolerate more moisture on favourable sites, extending its range into tundra and taiga conditions and elevations up to 2000 m above sea level in the southern portions of its adapted area. It prefers well drained, deep, loamy soils of medium and moderately coarse texture, including Chernozemic, Solonetzic, Regosolic, Brunisolic and Luvisolic soils. ''A. cristatum'' can tolerate salinity in the range of 5 to 15 mS/cm and prefers moderately alkaline conditions. It has low to medium fertility requirements. It will not tolerate prolonged flooding.

''Agropyron cristatum'' is the most shade-tolerant of the crested wheatgrasses, but does best in open conditions. ''A. cristatum'' is extremely drought tolerant. It achieves this drought tolerance by starting growth very early in the season, then going dormant from seed set until fall when it will exhibit vegetative regrowth if moisture is sufficient.

A recent study has shown that invasive populations of ''Agropyron cristatum'' have spread across the upper U.S. as well as southern Canada, and the invading ''Agropyron cristatum'' populations have been found to have a higher granivory than native grasslands and they maintain dominance even when native grassland species are reintroduced. This current study indicated that the increased granivory of ''Agropyron cristatum'' did not contribute to its competitive success. The study did show that although ''A. cristatum'' was found to have higher granivory, after 2 years the difference between ''A. cristatum'''s granivory and that of native species lessens, and that there was no apparent preference among the animals for either wheat. Therefore, the factors responsible for ''Agropyron cristatum'''s high granivore content are still relatively unknown.

''Agropyron cristatum'' is very tolerant of grazing, although under dry conditions new stands should be protected from grazing for at least two years as the seedling are slow to develop. ''A. cristatum'' can be damaged by several fungi, including leaf and stripe rusts, snow mold and some arthropods including black grass bugs in pure plantings.

Evolution

''Agropyron cristatum'' is one of several closely related grass species referred to as crested wheatgrass. It is unable to hybridize with its similar relatives, as it is a diploid species, whereas its closest relative, ''Agropyron desertorum'', is a tetraploid species. It was introduced from Russia and Siberia to North America in the first half of the twentieth century, and widely used to reseed abandoned marginal cropland undergoing varying degrees of soil erosion and secondary succession. ''A. cristatum'' is very long lived, with stands often remaining productive for 30 years or more.

Uses

''Agropyron cristatum'' has been bred into many cultivars selected for attributes ranging from forage yield to drought tolerance to turf types that will exhibit more pronounced degrees of rhizomatous growth habit. It has been and continues to be, widely used in both agricultural and industrial reclamation activities.

''Agropyron cristatum'' is known among other grasses and wheats for its relatively high granivory. Granivory describe the interaction between animals and seeds. ''Agropyron cristatums high granivory indicates that animals feed on the seeds of the plant as their primary, or even exclusive, food source. Although this raises concerns about the plant's continued ability to reproduce if its seeds are all being consumed, the high granivory of this species does indicate that ''Agropyron cristatum'' is an important food source. Studies have been conducted in search of the cause of ''Agropyron cristatums increased granivory, but as of yet a high relative granivory has not been proven to be a unique characteristic of ''A. cristatum,'' and could actually be attributed to factors other than the plant's genome, such as environmental conditions.

One promising factor that could lead to, and be responsible for, increased granivore in ''Agropyron cristatum'' is a certain genetic difference found on chromosome 6 of plants with a higher granivore content. Plants with a translocation on chromosome 6P yield wheat of greater weight and longer spike length than those without the mutation. ''Agropyron cristatum'' possesses higher tiller number, higher floret numbers, and greater resistance to various pathogens such as wheat rusts, powdery mildew, and barley yellow dwarf virus than many of its close wheat relatives. It has been used to cross-breed with other species of grass and wheat to transfer a greater disease resistance to them, as well as enhance their properties as a food source. This cross-breeding involves the transferring of the chromosome 6P translocation to the species it is cross-breeding with. Chromosome 6P of ''A. cristatum'' has also been proven to play an important role in regulating fertile tiller number and it possesses positive and negative regulators of tiller number. These regulators were specifically found to be on the 6PS and 6PL chromosome arms. High floret numbers and number of kernals per spike is controlled by genes located on chromosome 6P of ''Agropyron cristatum''. ''Agropyron cristatum''’s genes can be used to instill leaf resistance in other species of wheat. Three backcrosses between ''Agropyron cristatum'' and ''Aegilops tauschii'' produces a number stable, fertile lines of ''Aegilops tauschii'' that then has resistance to leaf rust. Also, multi-spike cultivars of ''A. cristatum'' have been found to be more stable agronomically and achieve higher yields than cultivars with large-spike type.

It is an easy grass to establish by seed, having both high germination rates and high seedling vigour. It also establishes rapidly relative to many other grasses. Under non-irrigated conditions in low precipitation areas, Crested Wheatgrasses are consistently some of, if not the, highest yielding and persistent of domestic forage grasses. However, ''A. cristatum'' is lower yielding, although it is slightly more palatable, relative to other Crested Wheatgrasses.

''Agropyron cristatum'' shows an immense toughness to a wide range of environmental conditions. ''Agropyron cristatum'' can be grown in cold temperatures, drought conditions, and relatively high amounts of salinity. It also has a resistance to barley yellow dwarf, wheat streak mosaic viruses, and leaf rust disease as well as containing high protein content.

''Agropyron cristatum'' is a highly competitive and persistent plant in drier areas, and has a moderate ability to spread by seed. As such, its use in and adjacent to remaining natural grassland communities within its adapted areas in outside its native Eurasian distribution has come under criticism as a factor in natural grassland biodiversity loss, although the subject is still being studied. One such fear is that its seedlings' emergence does not decrease under herbicide treatment.