Professor Anthony Trewavas: I yam convinced GM food is safe

The sweet potato was the first genetically modified food – 8,000 years ago, writes Professor Anthony Trewavas

The sweet potato  or yam  was genetically modified not by Man, but by nature. Picture: Getty

The sweet potato (commonly called a yam) is a familiar root vegetable on our supermarket shelves. The swollen root is highly nutritious, low in fat but high in vitamins A, C and fibre. It is easily grown and is eaten by one billion people world-wide. Hardy varieties are necessary for cultivation in the UK and are available from seed merchants. It is unrelated to the potato but it too can be roasted, fried, boiled, chipped and baked and acts as one of the recommended five-a-day. If you, too, have eaten sweet potato you have eaten your first genetically modified (GM) meal.

Some 8,000 years ago a bacterium (Agrobacterium) inserted two of its genes into the original sweet potato DNA, thus producing a GM sweet potato. These genes have been detected in some 300 varieties of yam but are absent in close wild relatives; they are expressed and cause tissues like the root to swell. Domestication was probably based on root size and thus continued propagation of its GM variety. These observations have considerable consequences for those that oppose GM crops.

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In one, well-publicised opposition statement it was argued that mixing genetic material from species that cannot breed naturally takes mankind into areas that should be left to God. While this statement is a matter of belief, the occurrence of an entirely natural GM yam surely suggests GM technology is a perfectly legitimate area of intervention for mankind, just as conventional plant breeding is legitimate. It was further claimed that cultivation of GM crops would cause ecological disaster and seriously damage the soil. The current annual world yield (125 million metric tonnes) of the GM yam is grown throughout Africa, Asia, the Americas and Pacific islands. Current growing area is about 12 million hectares. Has the predicted ecological disaster or soil damage followed cultivation? If it has, it is proving very well hidden.

One other commonly made objection is that these genes would contaminate natural environments and spread to wild relatives, and in particular, organic farms. Once released it was said “the genie could not be put back in the bottle”. If these genes from the GM sweet potato did at some time spread to other familiar close relatives, they are not there now. When this GM yam originated, agriculture was supposedly green, clean and entirely organic; it is thus a green, clean and organic product, contradicting completely the organic regulations that dismiss any form of GM agriculture or product. Is cultivation of the sweet potato now to be regarded as contaminating organic farms if grown nearby? If so, this will be the ultimate absurd contradiction.

The public have been subjected to enormous propaganda from green NGOs that claimed GM foods were unsafe to eat, that the process, being new, wasn’t adequately tested. But GM clearly isn’t new. Being eaten by a billion people worldwide with evident safety and for thousands of years, the GM sweet potato puts that claim to rest too. But these NGOs always relied on public ignorance of the years that current testing takes before any GM crop approval. Testing of any new product is essential, but claims that it is the GM process itself which represents some kind of undetermined danger is clearly wrong. Perhaps now we will no longer be subject to the claims that we are somehow all guinea pigs.

But other early actions of opponents – vandalising GM crop trial fields, for example – now look irrelevant when all the time the actual GM product, the sweet potato, resided happily on the shelf, untouched and unlabelled as GM. But what now looks equally uncalled-for are the bans on growing GM crops in a number of European countries, including that instituted by Richard Lochhead, cabinet secretary for food and the environment, here.

These bans are not based on evidence, as he admits, but incorrect perceptions about edible safety and Scotland’s supposed green, clean, food and drink industry that the GM sweet potato contradicts. Lack of leadership by our political class left a vacuum into which false opinions, malignant myths, and contamination were allowed to burgeon. People are entitled to their opinions; they are not entitled to their own facts.

Finally, opponents claim that GM manipulation is much more than just an extension of selective breeding techniques. But technology continually advances. A single gene can be selectively removed from its position in the crop genome and either moved to other places in the genome or replaced by one from another variety. In all respects this procedure is no different to conventional plant breeding but is certainly more precise, quicker and essential to increase yield with a concomitant reduction in land use and an aid to feeding a growing world population.

Professor Anthony Trewavas FRS FRSE, Scientific Alliance Scotland