Climate changes in the Fertile Crescent some 10,000 years ago lead to the spread of wild cereals, one of which was the predecessor of modern day wheat. Since those times, many genetic changes, brought about both by accident and by design, have led to a very different plant.
Wheat was originally a wild grass called einkorn. Around 10,000 years ago, this provided a staple diet for the hunter-gatherers in Mesopotamia and in the Tigris and Euphrates River valleys in the Middle East, an area called the Fertile Crescent. The amount of grain people could harvest from it allowed them to form permanent villages and marked the beginning of modern agriculture. Today, more foods are made with modern varieties of wheat, gradually modified over many centuries, than any other cereal grain.
When wild wheat is ripe, the seeds fall from the stem onto the ground, reducing the harvest. They are also enclosed in a husk. The transition to modern wheat, whose naked seeds remain attached to the stem, took place through chance hybridisations. These occurred between einkorn and other wild grasses in the Fertile Crescent. Each hybridisation resulted in a different combination of chromosomes (genetic information) and different characteristics in the offspring. In two such hybridisations, Einkorn (chromosomes AA) combined with two other wild grasses (BB and DD) resulting in Bread wheat (AABBDD).
As people in the Fertile Crescent harvested wheat, they tended to collect more of the grains that were firmly attached to the stem than the loose ones. Because this characteristic is passed on to future generations, once they started planting their own seeds, they grew far more of the variety with firmly attached and naked grains than that with loose grains enclosed in a husk. In this way, wheat began to change, so that today, in domesticated wheat, the grains remain attached to the stem in all plants. The genetic ancestors of today’s wheat can still be found in the Fertile Crescent and are still used for breeding experiments. For this reason, it is sometimes called the Wheat Gene Centre.
Since these serendipitous beginnings, further successes in wheat breeding have been achieved by intentional hybridisation or “crossing” and subsequent selection of successful outcomes. The use of crossing and selection led to the so-called green revolution of the 1960’s and 70’s, which saw increases in production of wheat by as much as 35%.
Crossings are not only possible between individuals of the same species but also, to a limited extent, between different species. For example, the crossing of hard wheat and rye resulted in Triticale, which combines the yield potential and grain quality of wheat with the agronomic features of rye, which can be grown in poorer soil conditions.
Conventional breeding programmes have clearly proved a powerful means of utilising the genetic diversity of crop plants to feed the world’s population. There is however a question mark over whether such methods will be adequate to feed the burgeoning population of the new millennium.