Common wheat explained

Common wheat (Triticum aestivum), also known as bread wheat, is a cultivated wheat species.[1] [2] [3] [4] [5] About 95% of wheat produced worldwide is common wheat; it is the most widely grown of all crops and the cereal with the highest monetary yield.[6]

Taxonomy

Numerous forms of wheat have evolved under human selection. This diversity has led to confusion in the naming of wheats, with names based on both genetic and morphological characteristics.

List of common cultivars

Phylogeny

Bread wheat is an allohexaploid a combination of six sets of chromosomes from different species. Of the six sets of chromosomes, four come from emmer (Triticum turgidum, itself a tetraploid) and two from Aegilops tauschii (a wild diploid goatgrass). Wild emmer arose from an even earlier ploidy event, a tetraploidy between two diploids, wild einkorn (T. urartu) and A. speltoides (another wild goatgrass).[8] [9] [10] [11] [12]

Free-threshing wheat is closely related to spelt. As with spelt, genes contributed from Ae. tauschii give bread wheat greater cold hardiness than most wheats, and it is cultivated throughout the world's temperate regions.

Cultivation

History

Common wheat was first domesticated in West Asia during the early Holocene, and spread from there to North Africa, Europe and East Asia in the prehistoric period. Naked wheats (including Triticum aestivum, T. durum, and T. turgidum) were found in Roman burial sites ranging from 100BCE to 300CE .[13]

Wheat first reached North America with Spanish missions in the 16th century, but North America's role as a major exporter of grain dates from the colonization of the prairies in the 1870s. As grain exports from Russia ceased in the World War I, grain production in Kansas doubled.

Worldwide, bread wheat has proved well adapted to modern industrial baking, and has displaced many of the other wheat, barley, and rye species that were once commonly used for bread making, particularly in Europe.

Plant breeding

Modern wheat varieties have been selected for short stems, the result of RHt dwarfing genes[14] that reduce the plant's sensitivity to gibberellic acid, a plant hormone that lengthens cells. RHt genes were introduced to modern wheat varieties in the 1960s by Norman Borlaug from Norin 10 cultivars of wheat grown in Japan. Short stems are important because the application of high levels of chemical fertilizers would otherwise cause the stems to grow too high, resulting in lodging (collapse of the stems). Stem heights are also even, which is important for modern harvesting techniques.

Other forms of common wheat

Compact wheats (e.g., club wheat Triticum compactum, but in India T. sphaerococcum) are closely related to common wheat, but have a much more compact ear. Their shorter rachis segments lead to spikelets packed closer together. Compact wheats are often regarded as subspecies rather than species in their own right (thus T. aestivum subsp. compactum).

Notes and References

  1. 23192148 . 2012 . Brenchley . R. . Analysis of the bread wheat genome using whole-genome shotgun sequencing . . 491 . 7426 . 705–10 . Spannagl . M. . Pfeifer . M. . Barker . G. L. . d'Amore . R. . Allen . A. M. . McKenzie . N. . Kramer . M. . Kerhornou . A. . Bolser . D. . Kay . S. . Waite . D. . Trick . M. . Bancroft . I. . Gu . Y. . Huo . N. . Luo . M. C. . Sehgal . S. . Gill . B. . Kianian . S. . Anderson . O. . Kersey . P. . Dvorak . J. . McCombie . W. R. . Hall . A. . Mayer . K. F. . Edwards . K. J. . Bevan . M. W. . Michael W. Bevan . Hall . N. . 10.1038/nature11650 . 3510651 . 2012Natur.491..705B .
  2. Book: Bonjean, Alain P. and William J. Angus . 2001 . The world wheat book: a history of wheat breeding . Andover, Massachusetts, US . Intercept . 978-1-898298-72-4 . 1131 . Excellent resource for 20th century plant breeding.
  3. Book: Caligari, P.D.S. and P.E. Brandham . 2001 . Wheat taxonomy: the legacy of John Percival . . . Special Issue No. 3 . 190 .
  4. Book: Heyne, E.G. . 1987 . Wheat and wheat improvement . Madison, Wis., US . . 978-0-89118-091-3 . 765 .
  5. Book: Zohary . Daniel . Daniel Zohary . Maria . Hopf . Maria Hopf . 2000 . Domestication of Old World plants: the origin and spread of cultivated plants in West Asia . . Oxford University Press (OUP) . 978-0-19-850356-9 . 316 . Standard reference for evolution and early history.
  6. Web site: Triticum aestivum (bread wheat). . 1 October 2016.
  7. 10.1016/j.envexpbot.2009.02.008. Occurrence of different inter-varietal and inter-organ defence strategies towards supra-optimal zinc concentrations in two cultivars of Triticum aestivum L. . . 66. 2. 220. 2009. Sanità Di Toppi . L. . Castagna . A. . Andreozzi . E. . Careri . M. . Predieri . G. . Vurro . E. . Ranieri . A. . 2009EnvEB..66..220S .
  8. 2016 . 7 . 991 . Mondal S, Rutkoski JE, Velu G, Singh PK, Crespo-Herrera LA, Guzmán C, Bhavani S, Lan C, He X, Singh RP . . Harnessing Diversity in Wheat to Enhance Grain Yield, Climate Resilience, Disease and Insect Pest Resistance and Nutrition Through Conventional and Modern Breeding Approaches . 10.3389/fpls.2016.00991 . 27458472 . 4933717 . free .
  9. 10.1126/science.1251788 . 25035500 . A chromosome-based draft sequence of the hexaploid bread wheat (Triticum aestivum) genome . . 2014 . 345 . 6194 . 1251788 . K. F. X. . Mayer. 206555738 .
  10. 10.1126/science.1250092 . 25035499 . Ancient hybridizations among the ancestral genomes of bread wheat . . 2014 . 345 . 6194 . 1250092 . T. . Marcussen. 206554636 .
  11. De Oliveira . Romain . Rimbert . Hélène . Balfourier . François . Kitt . Jonathan . Dynomant . Emeric . Vrána . Jan . Doležel . Jaroslav . Cattonaro . Federica . Paux . Etienne . Choulet . Frédéric . Structural Variations Affecting Genes and Transposable Elements of Chromosome 3B in Wheats . . 18 August 2020 . 11 . 891 . 10.3389/fgene.2020.00891. 33014014 . 7461782 . free .
  12. Matsuoka . Yoshihiro . Evolution of Polyploid Triticum Wheats under Cultivation: The Role of Domestication, Natural Hybridization and Allopolyploid Speciation in their Diversification . . 1 May 2011 . 52 . 5 . 750–764 . 10.1093/pcp/pcr018. 21317146 . free .
  13. Rottoli. Mauro. Castiglioni. Elisabetta. 19 April 2011. Plant offerings from Roman cremations in northern Italy: a review. . en. 20. 5. 495–506. 10.1007/s00334-011-0293-3. 2011VegHA..20..495R . 128545750. 0939-6314.
  14. 10.1007/s00122-002-1048-4. 12582931. "Perfect" markers for the Rht-B1b and Rht-D1b dwarfing genes in wheat. . 105. 6–7. 1038–1042. 2002 . 22854512. Ellis. M.. Spielmeyer. W.. Gale. K.. Rebetzke. G.. Richards. R..

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