GM wheat trial completely destroyed

Fungal resistance: An attractive, but difficult objective

(14 April 2003/4 May 2004) The trial field of genetically modified wheat near Bernburg (Saxony-Anhalt) has once again been destroyed. The trial, which has now been called off for good, aimed to show whether a new, genetically conferred trait – resistance to infection by harmful fusaria fungi – is also effective in field conditions. Fungi create problems for many crop species and conventional methods of control tend to provide inadequate protection. Genetic engineering could create new opportunities, particularly for wheat, grapevines and potatoes. But fungus-resistant varieties are still a long way from being ready to market.

Fungal disease in wheat. On the left normal grains of wheat, on the right shrivelled grains resulting from fusaria infection. (Photograph: Bavarian State Research Centre for Soil Culture and Crop Science, Munich)

Wheat is almost exclusively self-fertilising. Outcrossings to other plants are extremely rare. If GM wheat were grown, there would be fewer incrossings and contamination than with e.g. oilseed rape or maize.

Apple trees: Fungal diseases like apple scab and apple powdery mildew are a problem. Trials with new concepts were abandoned at the end of 2003.

Grapevines: Fungal infestation is currently controlled by spraying with chemical fungicides or, in the case of organic winegrowing, heavy metal preparations. It is difficult to breed fungus-resistant grapevines.

Potatoes: The pathogen that causes late potato blight, the fungus Phytophthora infestans (photograph above), is very adaptable. It is often one step ahead of the control strategies used by farmers and breeders.

On the 1st of April 2004 the Robert Koch Institute approved the two deliberate release trials scheduled for Saxony-Anhalt. A few days previously Greenpeace activists had sown organic wheat on the fields from paragliders, to hamper meaningful evaluation of the trials. Only the previous year, trials of the fungus-resistant wheat planned in Thüringen had been called off following similar actions.

According to the agribusiness Syngenta, which developed the fungus-resistant wheat and has already tested it in several countries, researchers were still able to prepare one trial field for sowing. During the night of the 4th of May, unidentified persons forced their way onto the site and pulled up the young wheat plants.

This year too, opponents had criticised Syngenta for failing to provide the public with detailed information about the type and origin of the genes that had been used to achieve the fusaria-resistance. Whilst Syngenta cited economic interests, critics argued that without more detailed information, people could not satisfy themselves that the GM wheat was safe.

However all information and documentation required for a safety assessment had been submitted to the Robert Koch Institute. As in the previous year the authorities saw no reason to refuse consent for the two planned trials on a total area of 850 square metres.

Resistance to fungi: the challenge for plant genetic engineering

Fungus-resistant wheat should be on the market in 2010 at the earliest. Any further delays would not be just down to the actions of protest groups and consumers' reservations about flour made from transgenic wheat. Compared with resistance to herbicides or insects, which have been introduced into many transgenic plants, resistance to harmful fungal infection is hard to achieve using molecular biological methods. Although various approaches are established, transgenic plants with genetically conferred fungal resistance are still at the developmental stage and most are a long way from commercial application.

And yet plants which resist infection by pathogenic fungi are an attractive and rewarding objective for breeders – not just because of the damage and yield losses, but also because conventional methods of control mostly tend to have drawbacks.

Wheat: First the fungi, and then the mycotoxins

Wheat plants infested with fusaria fungi produce small, shrivelledgrains in their ears. Some fusaria species can also produce various fungal toxins (mycotoxins). These can contaminate food when the cereal is processed. Mycotoxins can cause chronic and acute symptoms of poisoning, depending on the type and quantity.

Fusaria can normally be contained by selecting less susceptible varieties and using appropriate cultivation methods and chemical fungicides, thus reducing mycotoxin contamination. However, during severe infestations, particularly when the weather is hot and humid, these measures provided insufficient protection. Some new approaches have now been developed for producing fungus-resistant plants. They draw on molecular-genetic methods and findings.

The wheat developed by Syngenta contains a new gene from specific fusaria, which is responsible for "detoxifying" the mycotoxins.
Specific bacterial genes that trigger the production of substances like chitinase or glucanase , which destroy fungal cell walls, have also been inserted into plants. This approach is being tested with fungus-resistant grapevines, which have been released in the Franken and Pfalz winegrowing regions of Germany since 1999.
Another concept exploits a natural defence mechanism which infected plants use to protect themselves and to prevent the spread of the fungal infection ("hypersensitive reaction"). This method was used with potatoes to make them less susceptible to the pathogen which causes the infamous late potato blight (Phytophthora infestans ).

It has not yet been proven whether these new concepts will actually be effective and whether the resulting plants will be safe for people and the environment. But whoever sets out to answer these questions can hardly dispense with field trials.