GM CROPS - FOR GOOD OR EVIL - a response
Thanks to Jeremy Bartlett for this article - publication pending
GM Crops - for Good or Evil - a response
The speaker [Dr Ray Matthias of the John Innes Centre] at the lecture to Breckland Deanery Chapter Clergy in March 2000 (‘The Faith’, April 2000) used two arguments that are frequently made to support the development of GM crops.
Firstly, genetic modification is claimed to be far more precise than conventional plant breeding. Secondly, genetic modification is claimed to be the answer to a number of problems, one of which is how to feed the world's starving. However, neither of these claims is true.
Genetic modification is not more precise than conventional plant breeding. In a normal plant cross genes are swapped about but no new genes are introduced into the plant. This swapping about is under the precise, well-ordered control of the plant and has evolved over millions of years.
Genetic modification allows DNA to be introduced from other plants, animals, bacteria or viruses. To transfer a new gene into a plant, the gene first of all needs to be isolated, many copies need to be made and the gene must then be transferred into a receiving plant cell. This can be done using a bacterium that naturally infects plant roots, called Agrobacterium, or by firing the DNA containing the gene at high velocity into the receiving plant cell (the 'gene gun' method).
The rate of uptake of the new gene is very low. Whole plantlets have to be regenerated from the receiving plant cells and tested to see whether the transferred DNA actually inserted into the host plant's DNA. To do this, the tiny plantlets are grown in the presence of a selection agent. For herbicide tolerant plants, this can be the herbicide, but antibiotic resistance or simple colour changes can also be used.
There is absolutely no control over where the introduced DNA will be incorporated in the receiving plant's DNA. Existing genes may be disrupted or switched on by the inserted promoter, leading to unexpected effects. Already, various GM plants have unexpectedly had higher levels of toxins, extra fungal resistance, woodier stems or more starch, when none of these were the intended result of the genetic modification.
Genes cannot be considered in isolation. Genes tend to work in groups in an organised but barely understood way. Introducing new genes and DNA sequences, in combinations never ever known before, can disrupt gene function in ways we simply cannot predict.
If a single gene was transferred into a plant on its own, the plant's cells would recognise the foreign DNA as surplus to requirements and add chemical groups to inactivate it. Therefore a piece of DNA known as a promoter is also introduced into the plant. This has the effect of turning the gene on permanently, in all plant cells and tissues. The most commonly used promoter is from cauliflower mosaic virus.
In the natural state the cauliflower mosaic virus promoter is under the control of the virus and is locked away inside a protein coat. In recent years research has shown that both plant and animal cells contain dormant viruses, which would have infected the plant or animal's ancestors thousands or millions of years ago. Normally, including during conventional crossing, these are quite harmless. However, in the genetically modified plant, the viral promoter is potentially able to recombine with other DNA in the cell and either reactivate these viruses or even create new ones.
Plant genes are normally switched on and off in particular plant tissues according to the plant's needs (for example, bright colours in flowers but not in leaves, stems or roots). Environmental stimuli are also important (such as temperature changes or attack by caterpillars). However, inserted genes in a genetically modified plant are always switched on in every plant cell. In the United States, GM insect resistant crops are starting to become less effective, as the insect pests they were designed to resist rapidly develop tolerance.
Several genes are often introduced in a single genetic modification. The sugar beet grown at Stow Bedon this year actually contained seven different introduced DNA sequences, from different plants, viruses and bacteria. Sometimes, genetic modification accidentally introduces extra DNA that no one knows about. Monsanto's Roundup Ready soya variety has been grown commercially since the mid 1990s, but two extra DNA sequences were only detected early this year.
Is GM the answer?
Supporters of genetic modification often claim that it can help to save the poor from hunger. However, the causes of hunger are poverty, unfair distribution of land and people's lack of control over their own food supply. There is enough food for everyone - World agriculture currently produces one and a half times as much food as is needed to adequately feed the world's population. But food is unevenly distributed. During the Ethiopian famine in 1984, cash crops were still being exported to the rich countries of the world while people starved to death.
Lack of food means lack of nutrients. Worldwide, 230 million children are at risk of vitamin A deficiency but growing 'Golden Rice', a strain of rice genetically modified to contain beta-carotene (which the body turns into vitamin A) will do little to help. In India, grain stores are full yet people starve. Rice is freely available in markets, yet the 300 million people who live below the poverty line cannot buy - or grow - enough rice to meet their requirements. Whether this rice contains beta-carotene or not is therefore irrelevant.
A short term, but successful, answer to vitamin A deficiency is to supply high dosage vitamin A tablets twice yearly, alongside immunisation campaigns against diseases such as measles that exacerbate the deficiency. This approach works because the body can store vitamin A for up to six months. The cost of the tablets is about 4p per child. In contrast, the development of Golden Rice is very costly (hundreds of millions of dollars) and still only in the laboratory, requiring many more years of development.
The long term answer lies in self-reliance and local control of a varied food supply. Several programmes aimed at promoting traditional vitamin A rich foods are already proving successful. In West Africa, mangoes can be dried in simple solar driers and used as a year round source of beta-carotene. In Thailand, gourds supply a good source of beta-carotene, while India has many sorts of leafy vegetables, such as amaranth, spinach and coriander leaves. These crops can be grown on small patches of ground that cannot be used to grow rice. They are also good sources of minerals and other vitamins, which is important because someone on a poor diet will usually be deficient in these too.
It was once common practice to keep fish in paddy fields, where they provided a rich source of protein, fat and vitamin A. Where pesticides are used, this is no longer possible, but farmers in Bangladesh and China who have adopted organic farming methods are now able to do this and have seen rice yields rise by around 5 ? 15%, with a free extra 'crop' in the form of fish. Costs fall by about 80% as pesticides are no longer used and the incidence of malaria has fallen because the fish eat the mosquito larvae.
Worldwide, organic and low input agriculture offers ways of feeding
people, often with increased yields, while preventing the environmental
damage often caused by artificial fertilisers and pesticides.
Rejecting genetic modification does not mean rejecting biotechnology as a whole. The science of genomics allows scientists to map then follow useful genes during conventional plant crosses. Scientists trying to breed sweeter strawberries can quickly find out which offspring contain the desirable genes they want and speed up the breeding process but without the potential hazards and unpredictability of genetic modification. Using such techniques, it will be possible to produce new oil bearing crops or select new or under-used crop species.
In no way does rejecting genetic modification mean 'going back' but can offer modern, sophisticated ways of working with, rather than against, nature to solve our planet's needs.
Dr. Jeremy Bartlett.
Jeremy Bartlett has a PhD in Plant Genetics from Norwich's John Innes
Institute (now John Innes Centre) but currently works in computing.
He has taken an interest in the GM debate for the last three years and
has spoken at a number of GM Crop Trial meetings in Norfolk.