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Triticeae

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Triticeae is a tribe within the Pooideae subfamily of grasses that includes genera with many domesticated species. Major crop genera are found in this tribe including wheat (See Wheat taxonomy), barley, and rye; crops in other genera include some for human consumption and others used for animal feed or rangeland protection. Among the world's cultivated species this tribe has some of the most complex genetic histories. An example is bread wheat, which contains the genomes of three species, only one of them originally a wheat Triticum species. Seed storage proteins in Triticeae are implicated in various food allergies and intolerances.

Triticeae Genera

This list of tribes broadly follows that in Grass Genera of World Although there are taxonomic disagreements about the precise circumscription of some genera, this scheme is typical of those used in taxonomic literature. Aegilops (goat grasses - jointed goatgrass, Tausch goatgrass, etc)
Agropyron (crested wheatgrasses - Desert wheatgrass, quackgrass, etc)
Amblyopyrum ( Slim wheat grass - amblyopyrum)
Australopyrum (Australian wheatgrasses - velvet wheatgrass, pectinated wheatgrass, etc)
Cockaynea
Crithopsis (delileana grass)
Dasypyrum (Mosquito grass)
Elymus (wild ryes - blue wildrye, Texas ryegrass, etc)
Elytrigia
Eremium (Argentine desert ryegrass)
Eremopyrum (false wheatgrasses - tapertip false wheatgrass, annual wheatgrass, etc)
Festucopsis
Haynaldia
Henrardia
Heteranthelium
Hordelymus
Hordeum (barleys - common barley, foxtail barley, etc)
Hystrix (porcupine grass- bottlebrush grass)
Kengyilia
Leymus (wild rye- American dune grass, lyme grass,etc)
Lophopyrum (tall wheatgrass)
Malacurus
Pascopyrum(western wheatgrass)
Peridictyon
Psathyrostachys (Russian wildrye)
Pseudoroegneria (bluebunch wheatgrasses - beardless wheatgrass, etc)
Secale (Ryes - Cereal rye, Himalayan Rye,etc)
Sitanion
Stenostachys (New Zealand wheatgrasses)
Taeniatherum (medusahead - medusahead)
Thinopyrum (intermediate wheatgrass, Russian wheatgrass, thick quackgrass)
Triticum (Wheats - common wheat, durum wheat, etc)

Cultivated or Edible Species

Aegilops

  • Various species (rarely identifiable to species in archaeological material) occur in pre-agrarian archaeobotanical remains from Near Eastern sites. Their edible grains were doubtless harvested as wild food resources.
  • speltoides - ancient food grain, putative source of B genome in bread wheat and G genome in T. timopheevii
  • tauschii - Source of D genome in wheat

Amblyopyrum

  • muticum - Source of T genome.

Elmyus

Various species are cultivated for pastoral purposes or to protect fallow land from opportunistic or invasive species

Hordeum

Many barley cultivars

Leymus

Secale

Ryes

  • cereale (Cereal Rye) - Livestock feed and sour dough bread - 6 subspecies.
  • cornutum-ergot (Ergot of Spurred Rye) - herbal medicine at very low doses, deadly poisonous as food.
  • strictum - actively cultivated
  • sylvestre - (Tibetan Rye) - actively cultivated in Tibet and China highlands.
  • vavilovi (Armenian Wild Rye) - edible seeds, thickener

Triticum

(Wheat)

  • aestivum (bread wheat) - (AABBDD Genome)

    • compactum (club wheat)
    • macha (hulled)
    • spelta (hulled, spelt)
    • sphaerococcum (shot wheat)
  • monococcum (Einkorn wheat) (A Genome)
  • timopheevii (Sanduri wheat)
  • turgidum (poulard wheat) (AB Genome)

    • carthlicum (Persian black wheat)
    • dicoccoides (wild emmer wheat)
    • dicoccum (cultivated emmer wheat) - used to make Farro
    • durum (durum wheat)
    • paleocolchicum
    • polonicum (Polish wheat)
    • turanicum
    • turgidum

Genetics

 Genomes of some Triticeae genera and species
Genera & Species 1st 2nd 3rd
Triticum boeoticum AA
Triticum monococcum AMAM
Triticum aurata AUAU
Aegilops speltoides speltoides BB
Aegilops caudata CC
Aegilops tauschii DD
Lophopyrum elongatum EE
Hordeum vulgare HH
Thinopyrum bessarabicum JJ
Aegilops comosa MM
Aegilops uniaristata NN
Henradia persia OO
Agropyrum cristatum PP
Secale cereale RR
Aegilops bicornis SS
Amblyopyrum muticum TT
Aegilops umbellulata UU
Dasypyrum VV
Psathyrostachys NsNs
Psuedoregenia StSt
Triticum zhukovskyi AA AMAM GG
Triticum turgidum AA BB
Triticum aestivum AA BB DD
Triticum timopheevii AA GG
Stenostachys sp. HH WW
Elmyus canadensis HH StSt
Elmyus abolinii YY StSt
Thinopyrum Vjd =(V/J/D) JJ StSt VjdVjd
Leymus tricoides NsNs XmXm
Triticeae and its sister tribe Bromeae (possible cultivars: Bromus mango S. America) when joined form a sister clade with Poeae and Aveneae (oats). Inter-generic gene flow characterized these taxa from the early stages. For example, Poeae and Aveneae share a genetic marker with barley and 10 other members of Triticeae, whereas all 19 genera of Triticeae bear a wheat marker along with Bromeae. Genera within Triticeae contain diploid, allotetraploid and/or allohexaploid genomes, the capacity to form allopolyploid genomes varies within the tribe. In this tribe, the majority of diploid species tested are closely related to Aegilops, the more distal members (earliest branch points) include Hordeum (Barley), Eremian, Psathyrostachys. The broad distribution of cultivars within the Tribe and the properties of the proteins have implication in the treatment of certain digestive diseases and autoimmune disorders.

Evolution of the Tribe

One of the earliest branches in Triticeae, to Psuedoroegeneria, produces the genome StSt and another Hordeum then genome = HH. Allotetraploid combinations of Psuedoroegeneria and Hordeum and are seen in Elmyus (HHStSt), but also shows introgression from Australian and Agropyron wheatgrasses. Elymus contains mostly Psuedoroegeneria mtDNA. Like other polyploid genomic Triticeae.

Many genera and species of Triticeae are exemplary of allopolyploids, having more chromosomes than seen in typical diploids. Typically allopolyploids are tetraploid or hexaploid, XXYY or XXYYZZ. The creation of polyploid species results from natural random events tolerated by polyploid capable plants. Likewise natural allopolyploid plants may have selective benefits and may allow the recombination of distantly related genetic material facilitating at a later time a reversion back to diploid. Poulard wheat is an example of a stable allotetraploid wheat.

The Secale may be a very early branch from the goat grass clad or goat grasses are a branch of early rye grasses, as branch these are almost contemporary with the branching between monoploid wheat and Aegilops tauschii. Studies in Anatolia now suggest Rye (Secale) was cultivated, but not domesticated, prior to the holocene and to evidence for the cultivation of wheat. As climate changed the favorablitiy of Secale declined. At that time other strains of barley and wheat may have been cultivated, but humans did little to change them.

Goat Grasses and the Evolution of Bread Wheat

Tetraploidation in Wild Emmer Wheat

Aegilops appears to be basal to several taxa such as Triticum, Ambylopyrum, and Crithopsis. Certain species such as Aegilops speltoides could potentially represent core variants of the taxa. The generic placement may be more a matter of nomenclature. Aegilops and Triticum genera are very closely related as the image to the right illustrates the Aegilops species occupy most of the basal branch points in bread wheat evolution indicating that Triticum genus evolved from Aegilops after an estimated 4 million years ago. The divergence of the genomes is followed by allotetraploidation of a speltoid goatgrass x basal wheat species Triticum boeoticum with strains in the middle eastern region giving rise to cultivated emmer wheat.

Hexaploidation of tetraploid wheat

Hybridization of tetraploid wheat with Ae. tauschii produced a hulled wheat similar to spelt, suggesting T. spelta is basal. The tauschii species can be subdivided into subspecies tauschii (eastern Turkey to China or Pakistan) and strangulata (Caucasus to S. Caspian, N. Iran). The D genome of bread wheat is closer to A.t. strangulata than A.t. tauschii. It is suggested that Ae. tauschii underwent rapid selective evolution prior to combining with tetraploid wheat.

Wild Triticeae use by humans

Intense use of wild Triticeae' can be seen in the Levant as early as 23,000 years ago. This site, Ohala II (Israel), also shows that Triticeae grains were processed and cooked. Many cultivars appear to have been domesticated in the region of the upper Fertile Crescent, Levant and central Anatolia. More recent evidence suggests that cultivation of wheat from emmer's wheat required a longer period with wild seeding maintaining a presence in archaeological finds.

Pastoral Grasses

Triticeae has a pastoral component that some contend goes back to the Neolithic period and is referred to as the Garden Hunting Hypothesis. In this hypothesis grains could be planted or shared for the purpose of attracting game animals so that they could be hunted close to settlements.

Today, rye and other Triticeae cultivars are used to grazing animals, particularly cattle. Rye grasses in the New World have been used to selectively for use as fodder, but also to protect grasslands without the introduction of invasive old world species.

Triticeae and health

Glutens (storage proteins) in the Triticeae tribe have been linked with certainty to coeliac disease, certain complex allergic reactions and controversaly to other conditions. Triticeae glutens examines of the proteins of Triticeae, important in the link between gluten, gastrointestinal, allergic and autoimmune diseases that are primarily focused on the glutens of Wheat, Rye and Barley, but may also be triggered by similar proteins in Aveneae species or subspecies. Some of the recently discovered biochemical and immunochemical properties of these proteins suggest they evolved for protection against dedicated or continuous consumption by mammalian seed eaters. One recent publication even raises doubts about wheat's safety for anyone to eat Overlapping properties with regard to food preparation have made these proteins much more useful as cereal cultivars and a balanced perspective suggest a variable tolerance to Triticeae glutens reflects early childhood environment and genetic predisposition.

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