Genetically modified maize

Genetically modified maize (corn) has been engineered and is grown commercially in the United States. Currently there are two traits that have been engineereds into corn, these are resistance to the herbicides and incorporation of a gene that codes for the Bacillus thuringiensis (Bt) toxin, protecting plants from insect pests. Hybrids with both herbicide and pest resistance have also been produced.

Herbicide resistant corn

Corn varieties resistant to imidazolinone herbicides and Roundup have been produced.

Herbicide resistant corn is grown in the United States and was approved for import into the EU in 2004.

Bt corn

Bt corn is a variant of maize, genetically altered by methods of to express the bacterial Bt toxin, which is poisonous to insect pests. In the case of corn the pest in the European Corn Borer . This was achieved by inserting a gene from the soil-dwelling microorganism Bacillus thuringiensis into the corn genome. This gene codes for a toxin that will crystallize in the digestive tract of insect larvae, leading to its starvation.

In 2001 Bt176 varieties were withdrawn from the list of approved varieties by the competent US authorities.[1]

Bt corn and monarch butterflies

In May 1999 a laboratory at Cornell University published the resulats from a laboratory trial that appeared to indicate that the pollen of genetically modified Bt corn presented a threat to monarch caterpillars. Although this experiment did not duplicate natural conditions under which monarch caterpillars may come in contact with corn pollen, popular media reported that monarch butterflies were threatened.

In 2001 the scientific journal the Proceedings of the National Academy of Sciences published six comprehensive studies that showed that Bt corn pollen does not pose a risk to monarch populations for the following reasons:

• The density of Bt corn pollen that overlay milkweed leaves in the environment rarely comes close to the levels needed to harm monarch butterflies. Both laboratory and field studies confirmed this.
• There is limited overlap between the period that Bt corn sheds pollen and when caterpillars are present.
• Only a portion of the monarch caterpillar population feeds on milkweeds in and near cornfields.

The StarLink corn controversy

StarLink was a variety of Bt corn patented by Aventis Crop Sciences (a subdivision of Aventis, acquired by Bayer AG in 2002).

U.S. regulatory authorities permitted the commercial sale of StarLink seed, with the stipulation that crops produced must not be used for human consumption. This restriction was based on the possibility that a handful of people might develop an allergic reaction to a protein contained in the grain.

StarLink corn was subsequently found in food for people, with an episode involving taco shells being particularly well publicized. This led to a public relations disaster for Aventis and the biotechnology industry as a whole. Sales of StarLink seed were discontinued.

The southern portion of the U.S. corn belt planted the greatest amount of StarLink corn. It is this portion of the U.S. where corn borer damage creates the greatest economic loss to farmers.

There have never been any adequately controlled studies to determine whether StarLink actually poses any greater risk of allergic reaction than ordinary varieties of corn.

References

• Reuters. EU authorises Monsanto GMO maize for import, 26 October, 2004
• National Corn Growers Association (US). Approval Status of Biotech Corn Hybrids, 2005
• USDA. Butterflies and Bt Corn.