Emmer Wheat - The Domestication History of Triticum dicoccoides

The Ancient Parent of the Wheat Used in Bread and Pasta

Emmer wheat, farro (Triticum dicoccum), the oldest cultivated cereal, suitable for beer production, southern Germany, Europe
Emmer Wheat (Triticum dicoccum). Albrecht WeiaŸer / Getty Images

Emmer wheat (Triticum dicoccoides or T. turgidum ssp. dicoccoides) is the wild form of nearly all the domesticated wheat 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--it contains several attractive characteristics that could be used by other plants.

It is one of the traditional eight founder crops of the origins of agriculture.

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 8,500 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. Civan and colleagues (2013) have  suggested, however, that emmer wheat originated from a hybridized population of different wild lineages. 

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. Experiments in threshing rates indicate that the transition to a brittle stem reduces threshing time 35% in wild forms of emmer and a whopping 85% in emmer cultivars (Tzarfati et al.).

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 wheat, 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.

Emmer has been found to have accumulated several characteristics that make it an important source for improving other grains.

Identified attributes of emmer wheat include a set of stress-tolerance mechanisms--different varieties of emmer are more salt- or drought-resistant (Huang et al. 2016)--as well as a resistance to powdery mildew (Xie et al; Xue et al).

Sources

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