GM - boon or bane?

Constructive dialogue has to replace confrontation between pro- and anti-GM camps to allay people's fears, says Professor Geoff Dixon.

Protest: supporters and opponents of GM crops air their views outside the Rothamsted Research centre last May - image: Vic Shorrocks
Protest: supporters and opponents of GM crops air their views outside the Rothamsted Research centre last May - image: Vic Shorrocks

Soil Association chairman Monty Don has called for a "broadening of dialogue" between the anti- and pro-GM camps. This came at Kew's recent Diploma & Prizes Day. Constructive dialogue between the anti- and pro-GM sides would certainly be welcome as opposed to confrontation. Both start from a similar point that any new technology must be treated cautiously. Rachel Carson's Silent Spring graphically taught us that half-a-century ago.

Europeans have been healthily suspicious of plant and animal hydridisation since the mass importation of new species started in the 17th century. Subsequent eugenic experimentation and the Nazi holocaust increased fears and added reasons for caution. Inevitably, therefore, the attempted imposition of GM products by American companies, not least Monsanto in Europe, stirred public antagonism. The result is very suspicious shoppers and almost outright banning. Market surveys show that food labels that refer to GM ingredients, even those indicating their absence, raise public concern.

Two cropping approaches emerged in Europe. These were the pro-organic low-intensity and conventional high-intensity systems. Steadily over a decade, the two have converged as reliance on integrated crop management and environmentally benign land stewardship schemes emerged. But, regrettably, European public and consequently political opinion has prevented even the most rudimentary field testing of GM crops that might aid environmental care. Consequently, Europe has lost a major opportunity for becoming the world centre of independent excellence studying and assessing the agronomy of GM. By taking to the sidelines and erecting huge regulatory controls, Europe's commercial credibility as a centre for GM studies has virtually disappeared.

GM use outside Europe

Worldwide, GM is the fastest-growing new technology in the history of agriculture. In 2011, commercial GM crops were grown on 160 million hectares. Take-up of GM technology increases at five-to-eight per cent a year, producing a 94-fold rise since 1996. The mainstream broadacre agricultural crops like cotton, soya beans, maize (corn) and oil seed rape form the bulk of GM production. Their products are traded in the world's commodity markets. Although most GM crops are in China and South and North America, they are found in 32 countries.

For example, 99.5 per cent of Australia's cotton is GM to control insect pests, especially boll-worm (Helicoverpa armigera). The USA grows 50 per cent of the world's GM crops, while in China they are used by 13.3 million and in India by 7.1 million farmers. There are small areas of GM maize in the Czech Republic, Poland, Portugal, Romania, Slovakia and Spain. Europe's GM cropped area increased by 26 per cent in 2011. As early as 2000, two trillion GM plants grew in the world. Commercial horticultural GM crops include bean, carnation, chicory, melon, papaya, petunia, plum, poplar, potato, rose, squash, sweet pepper and tomato.

These come from 46 organisations including agro-biotech companies, research institutions largely in Brazil, China, India and the USA and a few European organisations. The current round of GM crops carry characters for herbicide resistance; insect, stress and disease resistance; altered qualities like flower colour; and pollination control. Information is available from the International Service for the Acquisition of Agri-biotech Applications (www.isaaa.org). Future GM crops will contain human nutritional and personalised medical features.

Pros and cons

Risks suggested for GM crops focus on the uncontrolled movement of genes that have been imported from beyond conventional breeding barriers. Can transferred genes (transgenes) move into wild relatives, perhaps changing their genetic diversity? That can only happen if a wild relative is present.

There is no risk, for example, from GM potatoes in Europe because wild relatives occur only in South America. Controlling such risks requires the use of isolation barriers not dissimilar to those used effectively in crop certification.

Another argument has been that GM plants possess survival advantages compared with non-modified types. As a result, uncontrollable "super-weeds" might displace native species. In conventional non-GM husbandry, groundskeepers do present management problems for growers. But there is no evidence of spread into native ecosystems. So why should GM plants be different?

Public anxiety centres largely on whether GM plants or their products are toxic to humans or wild and domesticated animals. In each suggested incident, subsequent detailed analysis has proved that the suspicions were unfounded. Naturally there must be intensive monitoring and that requires field experimentation.

Chinese studies show very positive benefits for natural biodiversity. In GM cotton crops grown on 2.6 million hectares, natural insect predators bio-controlling pests increased (Nature, vol 487, 362-5, 2012). Further benefits spilt over into neighbouring non-GM crops, boosting biodiversity across the landscape. In terms of reducing climate change, using GM crops saved the world 15.6 million tonnes of carbon dioxide emissions through reduced herbicide, pesticide and tillage.

Reducing herbicide use in intensely farmed maize-growing parts of the USA reduces risks to humans by improving drinking water quality. Overall, the US General Accounting Officer concludes that there is no long-term harm coming from these foods as compared with conventional ones.

Desirable horticultural characters

The biological potential for producing either trans- or cisgenic plants is huge. In reality, only those products possessing market value will be used. Currently, markets exist for GM cut flowers like carnation as developed by the Australian company Florigene (www.florigene.com.au).

Inserting genes coding for the flower colouring anthocyanidin chemical delphinidin produces mauve and violet shades. The GM crops are grown in Colombia and Ecuador and the flowers exported to the USA and Japan largely for the lucrative floristry markets.

Apples are one of the largest internationally traded horticultural commodities. Scab (Venturia inaequalis) and fireblight (Erwinia amylovora) are major causes of crop losses. Classical breeding produces new disease-resistant cultivars. But carving a market niche for these new cultivars is a long-term process. The market is very traditional and dominated by cultivars that are recognised internationally by consumers - such as Gala, Golden Delicious and Pink Lady.

This market differs significantly, for example, from bananas - the world's most popular fruit, but only recognised by the consumer at commodity level. Single genes coding for enzymes and other proteins that can inhibit or at least reduce the development of scab and fireblight can be achieved using cisgenic transfer from the Malus gene pool. That provides the apple market with disease-resistant cultivars retaining consumer image.

Similar cisgenic breeding is now used in strawberry and tomato. Providing disease resistance in these crops reduces chemical use, environment contamination and fruit residues. The clubroot (Plasmodiophora brassicae) epidemic currently threatening the Canadian oil rape crop (canola) has resulted in rapid breeding of cisgenic and transgenic resistant cultivars. Those resistances will be transferred into vegetable brassicas, especially in Asia and India, over the coming years.

Worldwide shortages of wood for timber, pulp and biodegradable packaging are stimulating interest in GM poplar (Populus). Field trials outside Europe are testing herbicide tolerance, insect resistance and control of flowering. GM virus resistance increases yields and incomes from basic crops like cassava, yams and plantains in Africa.

Increasing the nutritional value of crops like rice or brassicas combats insidious and destructive childhood diseases causing stunted growth and blindness and those of adult affluence such as coronaries and cancers.

Fruit and vegetables are ideal vehicles for increasing nutritional values, reducing allergenicities, enhancing processing qualities and providing personally tailored human medication. Each of these opportunities also brings chances for wealth creation - Europe might well be wise not to spurn them for too much longer.

Ethically acceptable GM

The early GM products predominantly imported genes across previously insurmountable biological barriers - this was termed transgenics. Objectors argued passionately that this is unethical. Such arguments deserve respect.

Equally, it must be recognised that all species of plants and animals have common evolutionary origins. Consequently, processes such as respiration are genetically similar in highly divergent organisms, even between plants and animals. Transgenics identifies a gene coding for a useful characteristic like cold tolerance in fish and then moves it into a crop plant.

Transfer requires the multiplication of the DNA that composes the gene, its movement into a suitable genetic background and then using a physical or biological system that inserts the gene into the receiving cells. Few cells will be successfully transformed and contain the transgene. These are bulked up by tissue culture and eventually produce a transgenic plant. Intense research worldwide over several decades has changed this process from being a long, tedious and frustrating series of laboratory experiments into standardised routine procedures.

Non-GM breeding moves genetic material between close relatives that naturally interbreed. This is a cisgenic process, meaning that the genes come from naturally sexually compatible donor plants. If modified using GM processes, the cisgenic plant is ethically acceptable because it contains no "foreign" genes coming from beyond the species barrier.

A further acceptable development is marker-assisted breeding. Inserting natural markers linked with the desired character provides the breeder with a signal of success. This technique is especially useful for perennial crops. Valuable characters like fruit colour or flavour are not apparent until long after the initial cross. Inserting a marker demonstrates early on whether the breeder has been successful.

Professor Geoff Dixon is managing director of GreneGene International.


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