Plant 251

Plant 251

Triticum aestivum L. (Poaceae)


Wheat grains, rich in starch and protein, are the most important food in Europe and much of the rest of the world.

Wheat belongs to a small genus of annual grasses whose distribution is concentrated in the Mediterranean and Fertile Crescent. Wheat fragments, from archaeological sites, provide some of the evidence for the Fertile Crescent being the cradle of western agriculture. Wild wheats, and their close relatives (goat grasses), produce grains annually, grow in large populations and are easily harvested. Consequently, nomadic or semi-nomadic peoples could have had access to predictable food supplies. Gradually, humans started to collect and grow the grains, and we became sedentary; becoming changed by the plants we farmed.

The basic outline of wheat origin has been known for over a century. Between half and three million years ago, wild wheat naturally hybridised with a goat grass to produce another type of wheat (wild emmer). Wild emmer was a successful evolutionary experiment; it spread throughout the Near East long before its use by humans. Twenty-three thousand years ago, in the Jordan Valley and Syria, early hunter-gatherers were using wild emmer and another type of wild wheat, einkorn. About ten millennia later domestication of both wild emmer and einkorn started.

Cultivated emmer, together with barley, became the staples of civilisations stretching from Egypt through Mesopotamia to the Indus Valley. Some seven to ten millennia ago, in Transcaucasia, hybridisation between cultivated emmer and another goatgrass produced bread wheat. About 2,000 years ago, bread wheat production overtook emmer production. Wheat domestication is the product of astonishing artificial modification of natural genetic variation.

To be successfully domesticated, wheat had to be a good food and have the right genetics. Adaptations that eased harvesting and increased grain production were important socially and biologically. The most conspicuous harvesting feature is that mature grains in cultivated wheats remain attached to the plant; wild wheats drop their grains at maturity. Theoretically, wheats that retain their grains can be selected from those that drop their grains in 20 to 100 years, although archaeological evidence shows this transformation took about 1,500 years. Another obvious change is that today's commercial wheats are much shorter than they were seventy years ago.

Adaptation of wheat to meet changing environmental and food needs is continual. Publication of a map locating all genes on the wheat genome offers the prospect of building wheat with precisely the characteristics to satisfy those needs.

Further reading

International Wheat Genome Sequencing Consortium 2018. Shifting the limits inwheat research and breeding using a fully annotated reference genome. Science 361: doi: 10.1126/science.aar7191.

Murphy DJ 2007. People, plants & genes. The story of crops and humanity. Oxford University Press.

Zohary D et al. 2013. Domestication of plants in the Old World. Oxford University Press.

Stephen Harris