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Emmer Wheat

Triticum dicoccoides

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Wild Emmer wheat (Triticum turgidum ssp. dicoccoides)

A spike of wild emmer wheat (Triticum turgidum ssp. dicoccoides), the progenitor of the cultivated tetraploid and hexaploid wheats, discovered 101 years ago in northen Israel.

Zvi Peleg

Emmer wheat [Triticum dicoccoides or T. turgidum ssp. dicoccoides (körn.) Thell] is the wild form of nearly all the domesticated wheats in the world, including both bread wheat (T. aestivum) and durum wheat (T. durum). Emmer is an annual, predominantly self-pollinated plant with large oval grains and brittle ears: it is too small and low-yielding to be of use to farmers today, except as a potential source of hybridization.

The earliest evidence of the use of emmer wheat is from the site of Ohalo II, where hunter-gatherers collected wild emmer about 23,000 years ago, on the shore of the sea of Galilee in what is today Israel. Based on the recovery of charred grains, Ohalo's residents processed the wheat into flour and baked it.

Domestication

Genetic investigations of the mutations of wheat genomes place emmer wheat at the center of the wheat domestication process, although the story is something of a complicated one. Current understandings (Peng and colleagues 2011) are that hunter gatherers began cultivating wild emmer about 11,300 years ago (Netiv Hugdud and other southern Pre-Pottery Neolithic A (PPNA) sites in Jordan), and within 2,000 years had created a cultivated emmer (T. dicoccum), and an early spelt (T. spelta), a hybrid form of emmer and goat grass (Aegilops tauschii). About 9,000 years ago, both emmer and spelt had mutated to a more easily threshed type of wheat. About 8500 years ago, bread wheat was created from a cross between domesticated emmer or a related free-threshing form and goat grass; and durum wheat had mutated from domestic emmer.

In the late 19th century, agronomist Aaron Aaronsohn discovered wild emmer wheat (T. dicoccon) growing near Rosh Pinna in Israel. Two different races of wild emmer exist today: one found in Israel, Syria, Lebanon and Jordan, and one in Turkey, Iraq and Iran. The one from the Karacadag region in Turkey is believed to be the progenitor of all the domesticated genotypes; although some evidence has found that multi-site independent domestication in both regions is a moderately strong possibility.

The differences between the wild version of emmer and its descendants include threshability (a combination of rachis fragility, and glume (husk) shape and tenacity. To successfully thresh grain after it has ripened in the field, you want a non-brittle stem and you want a hull that will peel off easily. Other traits selected for the domestic versions are enlarged seed size and nutrients leading to a higher and more productive grain yield.

The NAM-B1 Gene

A gene identified as a qualitative control for wild and domesticated emmer is called NAM-B1 gene. This gene slows grain maturation and creates a larger grain size, but at the same time decreases the amount of nitrogen, iron and zinc that moves from the leaves of the plant into the seeds. This gene is found in the wild and domesticated forms of emmer, but not typically in durum or bread wheats, and until recently it was believed to have been removed during the domestication process. A recent investigation into historic cultivars (Asplund and colleagues), however, found the gene still present in types from northern Europe until the mid-19th century. Asplund et al. argue that the conservation of this gene might have come about because of the need for early maturity in regions with a short growing season.

Sources

This glossary entry is a part of the About.com guide to the Domestication of Wheat, and the Dictionary of Archaeology.

Asplund L, Hagenblad J, and Leino MW. 2010. Re-evaluating the history of the wheat domestication gene NAM-B1 using historical plant material. Journal of Archaeological Science 37(9):2303-2307.

Brenchley R, Spannagl M, Pfeifer M, Barker GLA, D'Amore R, Allen AM, McKenzie N, Kramer M, Kerhomou A, Bolser D et al. 2012. Analysis of the breadwheat genome using whole-genome shotgun sequencing. Nature 491(703-709).

Dong P, Wei Y-M, Chen G-Y, Li W, Wang J-R, Nevo E, and Zheng Y-L. 2010. Sequence-related amplified polymorphism (SRAP) of wild emmer wheat (Triticum dicoccoides) in Israel and its ecological association. Biochemical Systematics and Ecology 38(1):1-11.

Özkan H, Willcox G, Graner A, Salamini F, and Kilian B. 2011. Geographic distribution and domestication of wild emmer wheat (Triticum dicoccoides). Genetic Resources and Crop Evolution 58(1):11-53

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Peleg Z, Fahima T, Korol AB, Abbo S, and Saranga Y. 2011. Genetic analysis of wheat domestication and evolution under domestication. Journal of Experimental Botany 62(14):5051-5061

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Peng J, Sun D, and Nevo E. 2011. Wild emmer wheat, Triticum dicoccoides, occupies a pivotal position in wheat domestication process. Australian Journal of Crop Science 5(9):1127-1143.

Sela H, Loutre C, Keller B, Schulman A, Nevo E, Korol A, and Fahima T. 2011. Rapid linkage disequilibrium decay in the Lr10 gene in wild emmer wheat (Triticum dicoccoides ) populations. TAG Theoretical and Applied Genetics 122(1):175-187.

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