Bread and the wheat from which it is derived are sold to us in down to earth language, as natural, plain and wholesome. Television advertisements employ pictures of bygone rural idylls, fields of golden corn ripening in the summer’s sun, with life simpler and slower, man and nature together in harmony. In reality this glorified grass which by the hand of man has risen from obscurity to become the commonest plant on earth, is so out of touch with nature that it has been unable to survive in the wild for millennia. Outside cultivation the top of the crops would be confined to history within a year or two.
Man has cultivated wheat for some 10,000 years, a practice recorded in the first book of the bible. However, far from being simple or natural its genesis is so complex that modern genetic engineers can only marvel at the complexity. Unlike the genetically modified crops that concern us today which contain just one or two genes from another species, bread wheat is an amazing three-way hybrid, assembled by combining all the genes from three different species of grass. To understand how this occurred requires an understanding of the mechanics of sex at a genetic rather than Kama Sutra level.
The fact that biologically sex is the combining together of cells from two individuals to form one new one hardly warrants explanation. A prerequisite to this sexual fusion is that the cells involved must first divide to reduce by a half the amount of genetic material they contain. The cells of most organisms contain two sets of chromosomes, one from each of their parents. Chromosomes are sausage like structures, which house genes. The cell division which produces, eggs, sperm, pollen or ovules is technically termed meiosis. It involves the pairing of parental chromosomes, such that each chromosome from the male parent aligns with its matching partner chromosome from the female parent. This allows the cell to subsequently divide in half equally, to produce daughter cells containing a single copy of each chromosome, while facilitating the shuffling of parental genes. If this fails to happen then the offspring of every generation would contain twice as many genes as did their parents. Indeed this is known to have occurred during the domestication of some crops, but what happened in wheat is even more complex.
If two unrelated species have sex, then the hybrid offspring they produce are usually sterile. The reason for this is that during meiosis in the hybrid, chromosomes from the different parents are unable to find a partner with which to pair and thus the process aborts. Occasionally these abortive cell divisions do so in such away that they produce viable cells containing duplicates of all the chromosomes present. The new doubled cells and their descendants are now fully fertile. Indeed they are technically, instantly a new species. This doubling provides each chromosome with an identical partner, with which to pair during meiosis, which enables fertility to be restored, but because they now contain as many chromosomes as both parent species put together, the new hybrid species is no longer able to interbreed with either of them. This miraculous hybridisation method of creating a new species has occurred not once but twice during the evolution of bread wheat.
The origins of wheat have been traced to the biblical lands of the Fertile Crescent. In this region a primitive cereal called Einkorn wheat, which relies on just a single set of chromosomes is still occasionally grown. Einkorn wheat was once thought to have been one of the three ancestral parents of modern wheat. Recent research points the finger of suspicion at a liaison between two unrelated wild grasses, with the Latin names of Triticum urartu and Aegilops speltoides. The hybrid species born from this pairing is cultivated in drier areas of the world such as India, the Mediterranean, and in parts of North and South America. It is used in making pasta and called unimaginatively pasta wheat, Durum wheat or in Latin, Triticum turgidum. Pasta wheat with its two sets of chromosomes was probably cultivated for many centuries before it also succumbed to the attractions of sex with one of its wilder relatives. On this occasion the act of adultery was with goat grass or Triticum tauschii which still grows as a troublesome weed in and amongst the cereal fields of the Middle East. The progeny of this match contain six sets of chromosomes, two from each of its three parent species. Other hybrids species of wheat produced from other crosses are also know in cultivation, but none are as widely grown as this Triticum aestivium or bread wheat, which occurs as several thousand varieties. Always quick to learn from nature, man has been using the same doubled hybrid method since the 1930s to continue the process further. Both pasta wheat and bread wheat have been artificially crossed with rye to produce an entirely new and vigorous cereal called triticale which has either six or eight sets of chromosomes.
Compared to the laboratory techniques of modern genetic engineering the hybridisation events that gave rise to good old-fashioned bread wheat are natural, in that they were not deliberately planed or manufactured. But there is no escaping the fact that it is genetic modification on a massive scale. The rare ‘natural’ chance events involved only occurred because mankind unwittingly loaded the odds in their favour by cultivating millions of wheat plants over thousands of years and then carefully selected and tendered generations of plants incapable of unassisted life.
Does the wheat story have any relevance to current concerns about genetically modified foods? The answer is probably yes, in that one of the genes that was incorporated into bread wheat from its goat grass parent codes for gluten production. This piece of genetic material enables wheat to produce large amounts of protein in its grains. This gluten protein is essential in the bread making process, because by trapping bubbles of carbon dioxide produced by the baker’s yeast it causes the dough to rise. Wash the starch out of a lump of uncooked dough by holding it under a running tap and you are soon left with just stringy elastic protein fibres. The gluten gene is therefore an important gene without which our daily bread would be hard and heavy. Unfortunately a minority of the human population is allergic to gluten, it causes irritation of the intestines and results in chronic diarrhoea. If a molecular geneticist had been responsible for incorporating a gene into an important basic food crop, which had such dramatic unpleasant consequences, the project would be stopped immediately. In addition to its impacts on human health, wheat has had even more dramatic effects on our environment. Being the most important crop on earth, millions of hectares of land have been put under the plough for its cultivation. On top of which by feeding the heaving mass of humanity it has facilitated even more damage to the global ecosystem. The impacts of this particular genetically modified crop are almost unimaginable. Perhaps it is time to start a campaign to ban wheat.