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Born Against
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For Elphaba and anybody else interested in learning more about genetically modified plants, here is a recent review article about the situation in the UK and Europe. It's a good review of the biology, the techniques, and the cultural obstacles involved in making use of the enormous human benefits of this technology.
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Annals of Applied Biology (2004),145:17-24.
Prospects for genetically modified crops
By NIGEL G HALFORD* Crop Performance and Improvement Division, Rothamsted Research, Harpenden, Hertfordshire, AL5 2JQ, UK (Accepted 4 May 2004; Received 20 February 2004)
Summary
Genetically modified (GM) crops have been in use commercially around the world for almost a decade. This review covers the successes and failures of GM crop varieties in that time, the current status of GM crop adoption and the traits that are being used. It also describes some of the GM crops that might come on to the market in the next decade. The barriers in the way of GM crop development in Europe, including consumer hostility, the difficulty in gaining official approval and discriminatory labelling laws are discussed. Key words: GM crop status, GM crop traits, future applications of GM crops, farm scale evaluations, GM food legislation and labelling
Introduction
Genetic modification using transgenesis is now an established technique in plant breeding. That is not to say that it is sweeping away every other technique, rather that it is an additional tool in the plant breeder's toolbox. All plant breeding, of course, involves the alteration (or, if you like, modification) of plant genes, whether it is through the crossing of different varieties, the introduction of a novel gene into the gene pool of a crop' species, perhaps from a wild relative, or the artificial induction of random mutations in the DNA of a crop plant through chemical or radiation mutagenesis. Recently, however, the term genetic modification has been applied to the technique of inserting a single gene or small group of genes into the DNA of an organism artificially. The methods available for the genetic modification of plants are described in detail elsewhere (e.g. Halford, 2003; Slater et al., 2003) and I will not describe them here. The technique has become established in plant breeding because it has some advantages over other techniques. These advantages are:
o It allows genes to be introduced into a crop plant from any source (although it is likely that the use of animal genes would not be acceptable to consumers, at least in food crops).
* It is relatively precise, single genes can be transferred (this is not possible in conventional breeding).
o Genes and their products can be tested extensively in isolation before use to ensure their safety.
* Genes can be "cut and pasted" in the laboratory to change when and where in a plant they are active, and to change the properties of the proteins that they produce.
There is also, however, a significant down-side for the plant breeder in using genetic modification to produce new varieties for the European market. This is that any genetically modified (GM) crop or food derived from it has to be approved for use within the European Union, and approval is extremely difficult to obtain. Furthermore, any food containing GM crop material above a threshold of 0.9% has to be labelled, while novel foods produced in any other way do not. This is preventing the development of new GM traits specifically for the European market. Nevertheless, the use of GM crops around the world continues to increase.
Current Status of GM Crops
Detailed information on the uptake of GM crops by farmers around the world has been provided for several years by Clive James at the International Service for the Acquisition of Agri-biotech Applications (ISAAA) (www.isaaa.org). In 2003, the ISAAA reported that GM crops were being grown commercially in 18 countries: Argentina, Brazil, Canada, Colombia, Honduras, Mexico, Uruguay and the USA in the Americas; Bulgaria, Germany, Romania and Spain in Europe; China, India, Indonesia and the Philippines in Asia; Australia and South Africa. Of these, Argentina, Brazil, Canada, China and the USA dominate in terms of total area. The global area of land planted to GM crops in 2003 was approximately 65 million ha, an increase of 15% on 2002. *Author E-mail:
More than half of this area is accounted for by herbicide-tolerant GM soybean, in fact more than half of the global soybean crop is now GM. The other major GM crops are maize (corn), cotton and oilseed rape (canola). There are also relatively small areas planted to GM virus-resistant papaya and squash and slow-ripening tomatoes.
GM Traits Being Used Successfully in Commercial Agriculture
The most successful traits to date (and it is difficult seeing them being overtaken) are those aimed at the fanner: herbicide tolerance (soybean, oilseed rape, cotton and maize) and insect resistance (cotton and maize). Traits affecting the quality or the nutritional value of the product have been more difficult to develop and market, but there are signs that these sorts of crops will become important in developing countries. It is fair to say, at present, that the number of traits that have been commercialised successfully is small.
Herbicide tolerance
Herbicides have been used since the 1950s, long before the advent of genetic modification, and are an essential part of weed control for farmers in developed countries. Most herbicides are selective in the types of plant that they kill and a fanner has to select a herbicide or combination of herbicides, applied at different times in the season, that is tolerated by the crop that he is growing but kills the problem weeds. Some of these herbicides have to go into the ground before planting, some pose a health risk to farm workers and some are persistent in the soil, making crop rotation difficult. They all require equipment and labour to apply and they all cost money.
Herbicide-tolerant GM crops were produced to overcome or reduce these problems. The first to be grown commercially were soybeans developed by Monsanto that were modified to tolerate the broadrange herbicide, glyphosate (Padgette et al., 1995). Glyphosate is relatively safe to use, does not persist long in the soil because it is broken down by microorganisms and is taken up through the foliage of a plant, so it is effective after weeds have become established. It is also relatively cheap. Its target is 5-enolpyruvoylshikimate 3-phosphate synthase (EPSPS), an enzyme in the shikimate pathway that is required for the synthesis of many aromatic plant metabolites, including some amino acids. The shikimate pathway is not present in animals, hence glyphosate's low toxicity to animals. The gene that confers tolerance of the herbicide is from the soil bacteriumAgrobacterium tumefaciens andmakes an EPSPS that is not affected by glyphosate.
Over 150 US seed companies now offer varieties carrying the trait and 81% of the US soybean crop in 2003 was glyphosate-tolerant (Benbrook, 2003). This success is due to simple factors: simplified and safer weed control, reduced costs and more flexibility in crop rotation. Overall, between 1995 and 1998 there was estimated to be a reduction of $380 million in annual herbicide expenditure by US soybean growers (Gianessi et al., 2002). However, farmers who used glyphosate-tolerant varieties had to pay a technology fee of $6 per acre. This reduced the overall cost saving to $220 million. Another report has suggested that although herbicide use fell with the introduction of these crops it has since risen (Benbrook, 2003). The fact that the GM system has led to a switch to conservation tillage systems which involve leaving weeds and stubble undisturbed over winter and then spraying with herbicide in the spring could explain an increase in herbicide use. If this is the case the consequent benefits of reductions in soil erosion and pollution from run-off would far outweigh the disadvantage of a modest increase in herbicide use. Nevertheless, it is not clear how these reports should reach such different conclusions. There are two other broad-range herbicide tolerant GM systems in use, involving the herbicides gluphosinate (or glufosinate) and bromoxynil, both marketed by Bayer. The gene used to make plants resistant to gluphosinate comes from the bacterium Streptomyces hygroscopicus and encodes an enzyme called phosphinothricine acetyl transferase (PAT). This enzyme detoxifies gluphosinate. Crop varieties carrying this trait include varieties of oilseed rape, maize, soybeans, sugar beet, fodder beet, cotton and rice. The oilseed rape variety has been particularly successful in Canada. Bromoxynil tolerance is conferred by a gene isolated from the bacterium Klebsiella pneumoniae ozanae. This gene encodes an enzyme called nitrilase, which converts bromoxynil into a non-toxic compound. So far this has only been used commercially in Canadian oilseed rape.
Interestingly there is a fourth broad-range herbicide-tolerance trait available in commercial oilseed rape varieties in Canada. The herbicide in this case is imidazolinone and the varieties were produced by Pioneer Hi-Bred, now part of DuPont. However, the trait was produced by mutagenesis, not genetic modification. Herbicide tolerance has now been engineered into many crop species and is undoubtedly the most successful GM trait to be used so far. In the USA in 2003,59% ofthe upland cotton and 15% ofthe maize was herbicide-tolerant (Benbrook, 2003), as well as the 81% of the soybean crop already discussed. Herbicide-tolerant soybeans have been adopted even more enthusiastically in Argentina and now account for 95% of the market, while herbicide-tolerant oilseed rape has taken 66% of the market in Canada. 18 Prospects for genetically modified crops
Insect resistance
Organic and salad farmers have been using a pesticide based on a soil bacterium, Bacillus thuringiensis (Bt), for several decades. The bacterium produces a protein called the Cry protein that is toxic to some insects but has no toxicity to mammals, birds or fish. Different strains of the bacterium produce different versions of the protein that are effective against different types of insects. Cryl proteins, for example, are effective against the larvae of butterflies and moths, while Cry3 proteins are effective against beetles.
The CrylA gene has now been introduced into several crop species (de Maagd et al, 1999) and the modified varieties are generally referred to as Bt varieties. As with herbicide tolerance, the benefits of using the insect-resistant GM crops depend on many factors, most obviously the nature ofthe major insect pests in the area (not all are controlled by Bt) and the insect pressure in a given season. However, Bt varieties have been successful in many parts of the USA (in 2003, 29% of the maize and 41% of the upland cotton crop was Bt) and Bt cotton in particular is gaining ground in Australia, China, India and the Philippines. Farmers who use Bt varieties cite reduced insecticide use and/or increased yields as the major benefits. A further, unexpected benefit of Bt maize varieties is that the Bt grain contains lower amounts of fungal toxins (mycotoxins) such as aflatoxin and fumicosin.
A different Cry gene, Cry3A, has been used to modify potato to make it resistant to the Colorado beetle. These GM potato varieties were withdrawn in the USA due to poor sales, farmers preferring to use broad-range insecticides instead. However, they may have a role to play elsewhere in the world where the Colorado beetle is a problem.
Virus resistance
There are two methods currently in use to genetically modify plants to be resistant to viruses. The first arose from studies into the phenomenon of cross protection, in which infection by a mild strain of a virus induces resistance to subsequent infection by a more virulent strain (reviewed by Culver, 2002). Modifying a plant with a gene that encodes the viral coat protein has been found to mimic the phenomenon.
An example of the commercialisation of this technology comes from the papaya industry in the Puna district of Hawaii (Ferreira et al., 2002; Gonsalves, 1998). After an epidemic of papaya ringspot virus (PRSV) in the 1990s almost destroyed the industry growers switched to a virus-resistant GM variety containing a gene that encodes a PRSV coat protein. The GM variety was successful and probably saved the papaya industry in Hawaii. The other method used to engineer virus resistance is to use antisense or co-suppression techniques (Grierson et al., 1996) to block the activity of viral genes when the virus infects a plant. Apotato variety carrying a replicase gene from potato leaf roll virus (PLRV) was marketed by Monsanto in the 1990s, later in combination with the Bt insect-resistance trait. These GM potato varieties have since been withdrawn in the USA because of reluctance to use them in the important fast-food industry. This technology is being applied to many other plant virus diseases, just one example of resistance being achieved at least under trial conditions being with potato tuber necrotic ringspot disease (Racman et al., 2001). It has tremendous potential for developing countries where losses to viral diseases are the greatest and have the most severe consequences.
Modified oils
Oilseed rape was first grown in the UK during the second world war to provide industrial oil, high in erucic acid (which is poisonous to humans), and these varieties are still grown today for that purpose. In the second half of the last century, however, varieties were bred with reduced levels of erucic acid and another group of poisonous compounds called glucosinolates. When these varieties were passed as acceptable for human consumption (oilseed rape received its seal of approval from the Food and Drug Administration of the USA in 1985), Canadian producers came up with the name Canola for edible oilseed rape oil. This name was adopted all over North America as the name not only for the edible oil but also for the crop itself. A problem for farmers who grow oilseed rape is that its oil is one of the cheapest edible oils on the market. The value of the crop is, therefore, relatively low and there is a lot of interest in increasing it. This has been achieved through genetic modification by introducing a gene from the California Bay plant that causes an accumulation of lauric acid to approximately 40% of the total oil content, compared with 0.1% in unmodified oilseed rape. Lauric acid is a detergent traditionally derived from coconut or palm oil.
A different modification has been made to the oil of soybean. In this case, the genetically modified variety accumulates oleic acid to approximately 80% of its total oil content, compared with approximately 20% in non-GM varieties (Mazur et al., 1999; Kinney, 1996). This was achievedby co-suppression (Grierson et al., 1996) of a gene that encodes an enzyme that converts oleic acid to linoleic acid. Oleic acid is very stable at high temperatures and at present the oil from the GM soybeans is used for industrial purposes. Relatively small amounts ofthese GM oilseed rape and soybean varieties are grown to contract, but those farmers who can get in on this business benefit from a premium price for their crop.
Slow-ripening fruit
Fruit ripening is a complex process that brings about the softening of cell walls, sweetening and the production of compounds that impart colour, flavour and aroma. The process is induced by the production of a plant hormone, ethylene. The problem for growers and retailers is that ripening is followed sometimes quite rapidly by deterioration and decay. Genetic modification has been used to slow ripening down or to lengthen the shelf-life of ripe fruit by interfering either with ethylene production or with the processes that respond to ethylene. This technology has the potential not only to improve the produce of western farmers but also to enable farmers in tropical countries to sell fruit to customers in Europe and North America. So far, however, the only examples of its commercial use are in tomato.
The first GM tomatoes with increased shelf life had reduced activity of an enzyme called polygalacturonase (PG), which contributes to cell wall softening. Afresh fruit GM tomato, Flavr Savr, with this trait was marketed by Calgene in the mid- 1990s but did not prove popular with consumers. Zeneca introduced the trait into tomatoes used for processing. The GM tomatoes have a higher solid content than conventional varieties, reducing waste and processing costs in paste production and giving a paste of thicker consistency. This product proved very popular in the UK from its introduction in 1996 until 1999 when retailers withdrew it in response to anti-GM hostility.
Some GM tomato varieties with delayed ripening are still on the market in the USA. They have reduced activity of the enzyme aminocyclopropane- 1-carboxylic acid (ACC) synthase, which is required for ethylene synthesis. ACC has also been targeted by Monsanto using a gene from a bacterium, Pseudomnonas chlororaphis, that encodes an enzyme called ACC deaminase, which breaks down ACC. A similar strategy has been adopted by Agritope, Inc., to break down another of the precursors of ethylene, S-adenosyl methionine (SAM), using a gene encoding an enzyme called SAM hydrolase. These products are not yet on the market but demonstrate that there is still considerable interest in modifying fruit ripening and shelf-life. The StarLink Incident
Not everything has run smoothly in the commercial application of GM crops. The most costly mistake involved several Bt maize varieties produced by Aventis (now part of Bayer) and marketed in the USA under the trade name StarLink. StarLink contained a different version of the Cry gene to that in other Bt varieties on the market (Cry9C instead of Cryl4) and was also tolerant of the herbicide gluphosinate. StarLink was not approved for human consumption but, inexplicably given that maize is an outbreeding crop, the Environmental Protection Agency approved StarLink for commercial growing as an animal feed in 1998. Inevitably, cross-pollination occurred between StarLink and maize varieties destined for human consumption and StarLink had to be withdrawn. Aventis agreed to buy back the entire StarLink crop of 2000 at a premium price.
Future Applications in GM Crops
Production of industrial oils and pharmaceutical fatty acids
Two examples of GM crops with modified oil content are described above but they are undoubtedly only the first of many. One application of this technology is in the production of oils with nutritional orpharmaceutical properties. Several oils produced by plants have pharmaceutical properties, including gamma-linolenic acid (GLA), which is found in borage and evening primrose, and arachidonic acid (AA) which is only found in a few mosses and fungi. GLA is used in the treatment of skin conditions such as atopic eczema and also has anti-viral and anti-cancer properties. AA is a constituent of breast milk and is important for brain and eye development in infants. The aim of biotechnologists is to take the genes that encode the enzymes responsible for making these fatty acids and engineer them into crop plants and there are already examples of this being done successfully (reviewed by Napier et al., 1999; Napier & Michaelson, 2001).
Nutritional value
Consumers in the developed world who take advantage of the world's harvest of fresh fruit, vegetables, bread, meat and dairy products that is available to them all year round probably have little need for an increase in the nutritional value of their food. Many, however, do not, and there is an argument for increasing the nutritional value offoods that consumers like rather than persuading consumers to change their diets. Nutritional value is also a selling point with some foods, breakfast cereals being a good example. Examples ofthe many potential targets for plant breeders and biotechnologists are folic acid, deficiency of which may cause gastrointestinal disorders, anaemia and birth defects, and the fat-soluble vitamins E and K, deficiencies in which are associated with arterial disease and, in the case of vitamin K, postmenopausal osteoporosis. Strategies for increasing 20 Prospects for genetically modified crops the levels of some of these nutrients are described by Herbers (2003). The real need for nutritional enhancement of foods, however, is in developing countries, where a limited amount and range of foodstuffs may be available or affordable. An example of a severe but avoidable health problem in poor countries is night and totalblindness brought about by vitamin A deficiency. This is associated in particular with a reliance on rice as a staple food and it is estimated that a quarter of a million children go blind each year because of vitamin A deficiency in South East Asia alone. There are many ways to tackle this problem and many have been tried but so far all have failed. One possible solution might be to address the low levels of vitamin A in rice (rice grain does contain vitamin A but only in the husk, which is discarded because it rapidly goes rancid during storage, especially in tropical countries). This has been achieved in an experimental GM rice line called Golden Rice (the name deriving from the colour of the grain) (Ye et al., 2000). Golden Rice actually accumulates ,Bcarotene (a precursor that humans can process into vitamin A) in its seed endosperm. The modification required the introduction of three genes, phytoene synthase (psy) and lycopene j3-cyclase genes from daffodil (Narcissus pseudonarcissus), and a phytoene desaturase (crtl) gene from the bacterium Erwinia uredovora. The enzymes encoded by these genes convert the compound geranylgeranyl diphosphate, which is present in rice endosperm, into a-carotene. This line was then crossed with another GM rice line which had been modified with a gene encoding phytase, an enzyme which breaks down phytate, a compound that prevents iron absorption, to make Golden Rice.
Golden Rice is not a commercial variety but the trait is being crossed into commercial breeding lines at the Rice Research Institute in the Philippines and by plant breeders in India. Even if these programmes are successful, it will still be several years before commercial varieties carrying the trait become available. Nevertheless, the potential of the work is extremely exciting.
Another target of great potential is improving the protein content of crops in terms of amount and quality. One example where this has been achieved is in potato at the National Centre for Plant Genome Research in Delhi. Tuber yield and protein content have been increased by introducing theArmaranthus hypochondriacus AmMA1 gene, which encodes a seed protein that is rich in essential amino acids (Chakraborty et al., 2000). Potato is not a major crop in India, but the same gene is also being introduced into rice, sweet potato and cassava. Improving nutritional value, particularly protein content and protein quality, is also relevant to the production of animal feed. However, although-some GM crops, for example soybean, maize, cotton and oilseed rape, are used for animal feed, there is currently no commercial use of a GM crop that has been modified specifically to improve its nutritional value to animals.
Resistance to fungal diseases
Fungal diseases of plants cause severe losses in crop production and an example of genetic modification being used to tackle the problem is in the engineering of potato to make it resistant to late blight (Song et al., 2003). Late blight is infamous as the cause of the Irish potato famine of the 19h century and still causes serious crop losses around the world today. The gene that was introduced into the potato line was called RB and came from a wild Mexican potato species called Solanum bulbocastanum.
Salt tolerance
Millions of acres of otherwise fertile land in developed and developing countries are rendered useless by salt build-up, usually as a result of irrigation. A possible solution to this problem has been developed using genetic modification to increase the rate at which a plant cell can remove salt from its cytoplasm and dump it in its vacuole. This involved the over-expression of a gene that encodes a vacuolar Nag/H' antiport pump (Apse & Blumwald, 2002). Tomato plants modified in this way can tolerate salt concentrations several times higher than non-GM plants and should survive comfortably in the salt concentrations of soils that are currently considered unusable. Salt accumulates in the leaves but the fruit remains edible and not salty at all. This means that removal and disposal of the leaf material after harvest actually cleans up the soil and a few harvests of the GM plants should return the soil to salt concentrations suitable for growth of other crops. Similar technologies are being developed to address the problem of contamination of soils with heavy metals.
Other traits
The above is not meant to be a comprehensive list. Other traits that might be developed commercially in the future include the ability to survive difficult climatic conditions (Araus et al., 2003), improved photosynthetic efficiency (Parry et al., 2003), the synthesis of non-food products such as pharmaceuticals, including vaccines (Mor et al., 1998), the synthesis of fragrances, pigments and industrial starch (Burrell, 2003), the removal of allergens (Tada et al., 1996) and the modification of metabolism (H-alford et al., 2003; Halford & Paul, 2003). Whether or not these advances are made will depend to some extent on the barriers that are put in the way of the development of the technology.
21 Barriers to the Development of Plant Biotechnology
Resistance to the use of GM crops is most significant in Europe. A major barrier is consumer hostility, driven in part by an intense anti-GM campaign waged by pressure groups. The UK government ran a public consultation exercise in 2003 called the 'GM Nation' debate. This consisted of public meetings organised around the country after which participants were invited to complete questionnaires. Entirely predictably these debates were dominated by the representatives of pressure groups and the result was an overwhelming rejection of GM crops and food. Real consumer attitudes are much more complex and difficult to gauge. A poll undertaken by the Institute of Grocery Distribution in August 2003 in the UK found that 47% of respondents were not interested in the ingredients in their food at all. Another 27% would prefer not to eat GM products but would not trouble to look at a label to avoid them, while 13% were happy to eat GM products but another 13% would actively avoid them. Clearly this is not a simple issue for retailers. The second barrier in Europe is one of legislation and official approval. This arose at first as an attempt to err on the side of caution as the new technology was introduced, but it is now clearly a political issue. If a GM crop is to be grown commercially in the EU it must first be granted a Part C consent by the European Commission. An application for consent is submitted to one of the 15 Member States, which becomes the lead Competent Authority (CA) for the application. If the United Kingdom is the CA for an application the dossier, which includes the results of safety testing and environmental risk assessment, is reviewed by the Joint Regulatory Authority, comprising the Department for the Environment, Food and Rural Affairs (DEFRA), the Scottish Executive, the National Assembly for Wales and the Department for the Environment in Northern Ireland. Advice is taken from the Advisory Committee on Releases into the Environment (ACRE), the Advisory Committee on Novel Foods and Processes (ACNFP) and the Advisory Committee on Animal Feeding-stuffs (ACAF). The CA returns the application to the European Commission with an accept or reject recommendation.
If acceptance has been recommended, a dossier is circulated to the other Member States, who have 60 days to make comment. If they all approve the marketing application the lead CA issues a Part C marketing consent, which applies across all Member States. In reality, one ormore Member States objects to every application and the Commission passes the dossier to its own Scientific Committee on Plants (SCP), which considers exactly the same questions already considered by ACRE. The SCP can consult two other committees, the Scientific Committee on Animal Nutrition (SCAN) and the Scientific Committee on Food (SCF), the equivalents ofACAF and ACNFP.
If the SCP recommends that approval be granted, the Commission asks the Members States to vote again, this time by the Qualified Majority Voting (QMV) procedure. If there is a QMV in favour the lead Member State should issue consent. But since 1998, France, Italy, Denmark, Greece, Austria and Luxembourg have blocked every application. The Commission then has the option of referring the application to the Council of Ministers, who can reject the decision of the Commission but only by a unanimous vote. If this does not happen the Commission should instruct the lead CA to grant consent. The Commission has been reluctant to use this option but appears to have become more assertive on the issue and has exercised it this year (2004) in the case of a Syngenta sweetcorn variety. However this variety is intended for import, not for cultivation in Europe. Three other products, a variety ofBt maize, glyphosate-tolerant soybean and tomato paste from GM tomatoes, have had such approval for many years.
Any food containing material from GM crops and sold in the EU must be labelled. Up to April 2004 vegetable oils, sugar and other refined products that do not contain DNA or protein are exempt from this rule, as are foods that contain small amounts (below 1%) of GM material as a result of accidental mixing and food sold in restaurants and other catering outlets (the UK government waived this exemption). In April 2004 the exemption for refined products will be dropped (although there are fears that this will lead to fraud since there is no way of policing it), the tolerance level for accidental mixing will be reduced to 0.9% and the law will be extended to animal feed.
The clear labelling of foods is entirely laudable, but the policy applies solely to GM crop products, not to new crop varieties produced by other methods or to the products of GM micro-organisms commonly used in yoghurts, cheeses and other foodstuffs. The policy could, therefore, be regarded as illogical and discriminatory. Nevertheless, the lack of a clear labelling policy when GM crop products first went on sale in Europe is one of the factors that led to consumer hostility.
The UK Farm-Scale Evaluations (FSE) Programme
In 2000 the UK government erected another barrier to the commercial use of GM crops. At that time a gluphosinate-tolerant maize variety, Chardon LL from Bayer, had been granted Part C consent and gluphosinate-tolerant oilseed rape and glyphosate- I 22 Prospects for genetically modified crops tolerant sugar beet were expected to be granted consent shortly after. The government negotiated a voluntary agreement with the companies involved that these varieties would not be marketed until a 3- yr programme of farm-scale evaluations had been carried out to compare the environmental effects of the GM crop and its non-GM equivalent together with the appropriate herbicide regime. The results of these studies were published in a special edition of the Philosophical Transactions: Biological Sciences of the Royal Society (Vol. 358, No. 1439, 29 November 2003).
These studies produced a huge amount of data and it is not possible to review it all here. In brief summary, it was found that for the sugar beet and oilseed rape varieties the numbers of weeds and consequently insects in the GM crop were lower than in the non-GM equivalent. This was widely reported as showing that GM crops were 'bad for the environment'. In reality it meant that the herbicide regime used with the GM varieties did what it was supposed to do. The possible advantages to the farmer of growing herbicide-tolerant GM crops (for example May (2003) estimated that sugar beet farmers could save £150 ha-' yr-') were not considered and different ways of using the crops and the herbicide were not included in the study. As a result, the Government has put off approval of these varieties until the companies involved, Monsanto and Bayer, can show that they can be used in an 'environmentally-friendly' manner. It is not clear whether Monsanto and Bayer are interested in doing this.
Both GM and non-GM maize were found to harbour fewer weeds and insects than the other crops studied (maize is taller and weed growth is restricted by shading). However, the GM variety was 'better' than the non-GM variety. In fact this relatively poor weed control was a concern to at least one farmer participating in the study (personal communication). However, the herbicide used on the non-GM maize in the study and used by most maize farmers in the UK was atrazine, which has just been banned for use within the EU because of its toxicity. The GM maize/gluphosinate combination represented a possible alternative.
In March 2004 the UK Government announced that it agreed in principle to the commercial cultivation of Chardon LL maize but that a number of constraints would be placed on its use. In April 2004 Bayer announced that, in view of the fact that details of these constraints had still not been made available, resulting in another period of delay, and that the variety was already 5 years old, it was not worth proceeding with commercialisation.
Conclusions
The GM crops that have been introduced so far and have been, in cases such as herbicide tolerant soybean, extremely successful will continue to be used by farmers around the world. It is also likely that the traits that have proved successful will be introduced into other crop species. Glyphosate tolerance, for example, has been engineered into a wide variety of crops from wheat to onions (Eady et al., 2003) and the wheat is already being considered for approval for commercial release in North America and Australia.
Despite this, the only significant use of GM crops in the European Union at present is the cultivation of Bt maize in Spain and it is almost inconceivable under the present circumstances that a company would develop a GM crop specifically for the European market. Europe might continue to get spinoff products with traits that have been shown to be successful elsewhere. However, biotechnology companies appear to be focussing more on gaining approval for the import of GM crop products from outside the EU rather than for cultivation within it. This means that European farmers may not be able to grow GM crops but they will have to compete with them.
Acknowledgement
Rothamsted Research receives grant-aided support from the Biotechnology and Biological Sciences Research Council of the United Kingdom. References
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