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The millet known as tef (Eragrostis tef) is a minor cereal crop on a global scale, but a major food grain in Ethiopia and Eritrea. In 2003–2004, for example, this grass was planted on around 2 million hectares, accounting for 28% of the 8 cereal crops grown in Ethiopia, and yielded more than 1.5 million metric tons. Tef can be grown under a wide range of conditions, including situations not suitable for other cereals. However, the national average yield of tef is very low, less than one metric ton per hectare, and the development of higher yielding cultivars would be very beneficial. The primary use of tef is for grinding into flour to make injera, the spongy fermented flat bread that is a staple food for most Ethiopians. In addition, the vegetative portions of the plant are an important source of fodder for livestock. Tef and several other Eragrostis species have been introduced to many other African countries, India, the United States, and Australia, mainly as specialty foods and forage crops. (Ayele et al. 1996; Zeller 2003; Yu et al. 2006 and references therein; Yu et al. 2007)
Tef has been grown in the Horn of Africa for at least 2,000 years. The domestication history of tef appears to be different from that of some other cereals (a factor which may explain the difficulty encountered in identifying many Eragrostis seeds in archaeological samples). In contrast to the domestication of many grains, selection of large seed size and intensified tillage were not key factors in tef domestication. Early cultivators were likely selecting for increased branching and higher percentage seed set under conditions of minimal tillage. (D'Andrea 2008)
Yu et al. (2006) constructed and analyzed an expressed sequence tag (EST) library as a resource for genetic research on tef. All tef cultivars that have been assessed are tetraploid, with a base chromosome number of 10 (2n = 4x = 40). The genome size of tef is roughly 50% larger than that of rice, small enough that it should be amenable to molecular mapping and analysis. (Ayele et al. 1996) Yu et al. (2007) mapped agronomically important quantitative trait loci for use in marker-assisted breeding programs.
The direct wild progenitor of Eragrostis tef is generally believed to be E. pilosa, a weedy species that occurs throughout the world in tropical and temperate regions and is common in Ethiopia. The only documented and consistent morphological distinction between E. pilosa and E. tef is spikelet shattering. The multi-floreted spikelets of E. pilosa readily break apart at maturity as a natural mechanism of seed dispersal, whereas the lemmas, paleas, and caryopses of E. tef remain attached to the rachis at maturity, which facilitates harvesting. Because of its importance in allowing farmers to control seed dispersal, the transition from shattering to non-shattering is one of the most common features seen in the domestication of grains. (Ingram and Doyle 2003)
Tef has been grown in the Horn of Africa for at least 2,000 years. The domestication history of tef appears to be different from that of some other cereals (a factor which may explain the preponderance of indeterminate Eragrostis seeds in archaeological samples). Selection of large seed size and intensified tillage were not key factors in tef domestication. Early cultivators were likely selecting for increased branching and higher percentage seed set under conditions of minimal tillage. (D'Andrea 2008)
