Genetically Modified Maize

Source:
Production Estimates and Crop Assessment Division, FAS, USDA (August 1999)

2. The principal uses of the maize harvest

78% of the maize harvest is used as animal feed, in particular for cattle, pigs, and poultry. Thirteen percent is used as human food, e.g. as grain maize or polenta or in processed form such as oil, starch, glucose syrup, dextrose, and flour. An important role is also played by the so-called "extruder products": here maize is processed to manufacture snacks such as peanut flips.
Maize derivatives are also used in pharmaceutical products such as tablets, in cosmetics and soaps, and in industrial products such as chemicals, insecticides, adhesives, paints, solvents, and lacquers.

Principal uses of the maize harvest

Source:
Arthur D. Little (1997).

3. Food products that contain maize

In its processed forms as oil, starch, glucose syrup, dextrose, and flour, maize is an ingredient contained in a wide range of food products.

Source: Gesprächskreis Grüne Gentechnik (GGG), Genius Biotechnologie GmbH, Dr. H. Mahlmann, Cerestar, 1998.

Important: The Bt maize produced by the Novartis company which was already approved in 1997 is not a novel food, and special labelling regulations apply here (see section 6.4).

4. The corn-borer larva

The corn-borer larva is one of the most damaging pests in maize cultivation. Each year it destroys 7% of the worldwide maize harvest (42 million tons). This amount would fill the Cheops pyramid - the largest pyramid in the world - seventeen times over. In some regions in North America and Europe, the larva is responsible for the destruction of as much as 20% of the harvest. Scarcely has it hatched out of its egg than the corn-borer larva drills into the stem of the maize plant. By pupation it will literally eat its way through the plant. Today plant-protection agents are used to combat the corn-borer larva, at a cost of 20 to 30 million dollars each year in the United States alone. The moment of application is critical, as the use of spraying agents is ineffective once the corn-borer larva sits in the middle of the stem, protected from the agents. In total, the damage incurred in the United States as a result of corn-borer infestation amounts to roughly one billion dollars each year; in France the damage is estimated to be about 50 million Euro.

5. The soil bacterium Bacillus thuringiensis

The soil bacterium Bacillus thuringiensis (Bt) has a lethal effect on specific insect larvae.
When a butterfly larva eats the bacterium, the Bt protein produced by the bacterium is cleaved in the intestine of the larva. This in turn results in the production of a new protein that leads to the development of holes in the intestine of the butterfly larva, which then starves and perishes.
In agriculture the highly specific effect of the Bt proteins has been used to combat pests for some 40 years now. Processed into biological spraying agents, they are, for instance, used in vegetable cultivation against the cabbage caterpillar or the Colorado potato-beetle larva, and in maize-cultivation to combat the corn-borer larva.
Spraying agents prepared from Bt proteins are ideal from the ecological viewpoint. They degrade rapidly in the soil to form harmless substances. A drawback with maize is, as indicated above, that once inside the stem, the corn-borer larva is protected from the Bt spraying agents.

6. Maize that protects itself against the corn-borer larva

Novartis has succeeded in producing a genetically modified form of maize that protects itself against the corn-borer larva by producing the Bt protein of Bacillus thuringiensis in its leaves, stem, and pollen - hence the name Bt maize. Thus when the larva begins to bore its way into the plant, it dies.
In 1997, farmers worldwide were already cultivating genetically modified, corn-borer-resistant maize over an area of 3.2 million hectares - in 1998 this acreage had grown to 8.3 million hectares equivalent to 30% of the total global transgenic area for all crops (ISAAA, C. James, 1998). For the first time, in 1998, transgenic Bt maize was cultivated in countries of the European Union with approximately 20,000 hectares in Spain and 2,000 hectares in France. The total number of countries growing transgenic corn in 1998 was six: USA, Canada, Spain, France, Argentina and South Africa.
Bt maize has also been granted a licence for import and further processing by Japan (approved as an animal feed and as human food).

Additional genes in Bt maize

Europe is virtually self-sufficient in maize, and consequently we import only a small percentage of our maize products from abroad. GM maize is generally found in imported products that have been manufactured in the USA (In the UK, e.g. M&S 'Jelly Belly' jelly beans). The limited amounts of GM maize that are currently grown in Europe (in France and Spain only) are licensed solely for use in animal fodder.

The development of genetically modified plants often requires so-called marker genes. These serve the purpose of identifying those plant cells into which the desired gene has been successfully incorporated. The marker genes are transferred linked to the target gene (e.g. the gene for the Bt protein). Using these markers, once the transfer experiment has been carried out, the scientist can select those cells that have taken up the genes. This is important, since only a relatively small proportion of the cells used actually take up the genes.
In addition to the Bt gene, Bt maize contains two marker genes; a herbicide-tolerance gene and the gene for ampicillin (an antibiotic) resistance. Bt maize lines of the most recent generation no longer contain any antibiotic-resistance genes.
The issues arising from the use of antibiotic-resistance genes such as the ampicillin-resistance gene are discussed in detail in sections 6.3.4 and 7.4.
The herbicide-tolerance gene in Bt maize renders the plant resistant to the herbicide BASTA (Liberty) produced by AgrEvo. There was no selection regarding a high degree of herbicide tolerance - the only aim of this development was resistance towards insects, which is why this maize cannot be used as a herbicide-tolerant maize variety. An example of a LibertyLink®-tolerant plant has been described above in section 5.1. With the Maisgard® (Yieldgard®) varieties, Monsanto has developed a corn-borer-resistant maize and also a herbicide-tolerant Roundup-Ready® maize.

7. Who benefits from the corn-borer-resistant maize?

After sowing the Bt maize crop, farmers need no longer worry about infestation with the corn borer - the plants protect themselves against the pests. This results in a reduction in the use of plant-protection agents. Harvest yields are as much as 15% higher than those achieved with the cultivation of conventional maize lines (see following table).
The built-in protection is independent of the weather and is effective in all parts of the plant. By contrast, Bt spraying agents no longer have any effect when they are washed off the plants by rain, nor when the larvae reach the inside of the stem.

Environmental benefits of Bt maize include decreased use of mineral fertilizer, fossil fuels, and plant-protection agents. Because Bt maize reduces harvest/crop losses, as much as one fifth (2.5 million hectares) of the acreage currently under maize cultivation could be released to other agricultural uses. Finally, efficient agricultural production contributes towards reducing the costs in the food-production sector.

Savings made possible by Bt maize that benefit the environment

Source: Novartis, Gafta.

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