GENETICALLY MODIFIED (GM) CROPS By Professor Neil Jones, The University of Wales, Aberystwyth, Institute of Biological Sciences.
The Lloyd George Society is not exclusively devoted to the study of the career of David Lloyd George, or to considering aspects of Welsh, British or international politics, although it is fair to say these are our main interests. The Society invites guests to its weekend schools from a range of professions and specialisms. Professor Jones’ article is based on a talk given at a meeting of the Lloyd George Society held at Llanwyrtd Wells, Powys in February 2001.
It is copyright and no part of it may be reproduced without the permission of the author or the Society. It was first published by the Society as one of four papers delivered at the weekend school of 9-10 February 2001. Please note the science and technology of GM crops may have moved on since the lecture was given.
The starting point for the debate about GM Crops has to be what we mean by crops in the usual sense in which we use this word. With very few exceptions none of our modern day crops are wild plants. They are domesticated forms of their wild relatives, which have been selected and bred by humans over long periods of time, and in many cases they no longer resemble their wild ancestors. In many cases too, we no longer know their ancestry.
Take as a familiar example the cauliflower. Its wild relative is a weedy species of Brassica oleracea, which still grows in this country and it resembles the rape, which we often see by the roadside. The cauliflower is actually an inflorescence with about 10,000 immature flowers making up the edible parts. It had been produced by selective breeding under domestication and it is the same species as the Brussels sprout, the kohlrabi, the kale, the broccoli and the cabbage which all originate from the wild Brassica oleracea following selection for different edible parts of the plant. These crops are ‘genetic monsters’ and they share this attribute with many others, e.g. wheat, maize, potatoes, sugar beet, rice and tomatoes to name but a few.
In the breeding of these crops, to improve their productivity and their nutritional properties, we have altered them greatly from their wild ancestors and in making them edible we have stripped them of their natural defences against a multitude of pests and diseases. To grow them productively, and to minimise losses, we now have to protect them by the use of chemical pesticides and insecticides (or use organic husbandry practices). Breeding can also include introducing natural genes for resistance, as well as the continuous process of ever increasing yields and improving nutritional properties. This breeding is not an exact science. It may begin by crossing together existing varieties of a crop, or trying to bring in variation from a wild relative but in any event the initial crossing combines many thousands of genes from the parent plants involved and these have then to be sorted out over many further cycles of crossing to try and end up with the introduction of just a few useful traits.
Gm crops offer a new way of breeding, which is more exact, and which allows us to move single genes from one species into another even when the species concerned are unrelated or even from different kingdoms – genes from a jellyfish into a potato for example. What has happened to make this new technology of recombinant DNA possible? The answers go back to the 1970s when scientists discovered how to take DNA out of one species, cut it into tiny pieces at very particular places and then stitch one tiny piece (a gene) into the DNA of any other species. The science has moved on now to the point where a single useful gene from one species can be cloned in the laboratory and then introduced into a host crop species by using some natural vector, like a bacterium, to carry it into the cells of the host where it will insert itself into the host’s chromosomes and thereby make a genetically modified organism. Another method of gene transfer is to make multiple copies of a useful gene; coat gold pellets with these genes and then ‘shoot’ them into a host crop plant using a DNA gun. In any event it is now routinely possible to place a gene from any living organism into any other one. All living organisms share the same genetic code after all.
The idea of this kind of genetic engineering has provoked two kinds of reaction: some find it tremendously exciting to be able to manipulate crop plants in such a precise way for the benefit of humans, and others find it frightening.
What kind of new plants are being made? Soya, resistant to herbicides: spray the crop and kill all the weeds, leaving the soya crop. Maize resistant to the corn borer insect (the grub), using a gene from bacterium; rice enriched with vitamin A, using a gene for a beta-carotene from daffodils; dustbin crops (rape, poplar, tobacco) that will soak up pollutants such as mercury from the soil; bananas, for producing edible vaccines; tobacco engineered to produce drugs to treat ovarian cancer; plants with new architectural properties.
We already know since the year 2000 of all the genes in the model plant species Arabidopsis thaliana (thale cress, a brassica from the cabbage family): its genome has been entirely sequenced. [2001] has seen the completion of the sequencing of the genome of rice, a member of the gramineae – grasses and cereals.
All plants have essentially the same genes, so with this new information it can now be said that we know virtually all of the genes that exist in our plant crops. Genetic engineering will now use this knowledge to restructure plants, i.e. make GM plants using other plant genes – is this not acceptable?
A major concern of GM crops is that they may be harmful to health, although no such harmful effects have yet been discovered since the first transgenic plant was made in 1984. Given the level of testing involved, as in GM soya (which was eaten for three years) for example, where the level of protein component is completely defined in biological terms, it could be said that GM crops are the safest foods we can eat. Who knows all the chemicals in a cauliflower, or if it has small negative effects on health? Who knows how dangerous the mycotoxins (poisons produced by fungal pathogens in wheat grains) are that are found in flour made from wheat? They can be fatal. DNA is not harmful to eat. We eat the genes of a wide spectrum of organisms all the time – when we eat fresh fruit and vegetables, yeast in beer, live oysters, lightly cooked fillet steak, raw fish, mussels, bacteria in yoghurt, fungus in cheese – we actually eat the entire genome of these organisms.
Nonetheless, we must be aware of possible risks, whatever they might be. To say we should be risk free is to ask too much. On this basis we would not have, for example, vaccines against polio, blood transfusions, antibiotics, or do any surgical procedures in hospitals, or have any vehicles on the roads, or smoke cigarettes or do many things where the risk factors may be of a high order. We accept engineered foods, such as nutribread, which contains sex hormones for post-menstrual women, margarine which contains wood pulp to reduce levels of cholesterol in the blood, and in the United States, foods with synthetic drugs, alternative medicines and growth hormones. Why do we accept engineered foods but not GM crops?
Are GM crops harmful to the environment? Only testing will give us the answer to this question. To put the issue in context we have to realise the harm we are already doing to the environment by modern intensive agricultural practices: namely the loss of biodiversity, loss of the soil, resistance to man-made pesticides and herbicides. It is estimated that more than 500 species of insect are already resistant to widely used insecticides and that over 200 species of weeds are evolving resistance to herbicides used as crop sprays. No new form of resistance due to GM crops is known. And it is often argued that by using GM crops we can drastically reduce the application of chemical sprays onto our crops – as with cotton in the southern United States and China.
Will GM crops escape into the wild, or cross-hybridise with wild species? In most cases in the UK this is impossible. There is no wild wheat, no wild maize, and no wild tomatoes. The main concern is with oilseed rape, which can cross-pollinate with wild species, so this problem has to be solved. Should we ban GM maize and wheat just because rape might be at risk?
Will the issue of GM crops go away? The answer is no. In China alone there are now 1,000 research institutes as well as American and European Universities undertaking GM research and making new GM crops. When we get a new GM crop (say broccoli),which has anti-cancer properties, do we imagine that people will decline to eat it or that they should be denied the choice to do so?
