Apr 11, 2002

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Fungus-resistant grapevines

An attack on the winegrowing industry?

In the late nineties the Geilweilerhof Institute of Grapevine Breeding at the Federal Centre for Breeding Research on Cultivated Plants conducted the first deliberate release trials on genetically modified grapevines in the Franken and Pfalz wine-producing regions of Germany.

This caused great alarm at the time. Critics complained of an “attack on the winegrowing industry” and many winegrowers believed that the good reputation of German wine was at stake. There were calls for a ban and petitions, even proposals and debates in the Bavarian Landtag. The Bund für Naturschutz (the German branch of Friends of the Earth) spoke of “incalculable risks to people and the environment”.

In all around 200 genetically modified grapevines are being tested in field conditions.

The aim: Resistance to harmful fungi

Fungal pests, and in particular grey mould, powdery mildew and downy mildew in European regions, are a major problem in winegrowing. They not only reduce the yield of the vines, they also lead to losses in wine quality. Most winegrowers today have little alternative than to apply chemical fungicides. At times of heavy infestation and in sensitive areas they may spray up to eight times. Even organic winegrowers are still searching for a reliable method to combat the dreaded fungi. For a long time they used copper preparations, which resulted in contamination of the soil with heavy metals. Some organic winegrowers now use clay and plant extracts; this enables them to manage without copper salts in years of low fungal infection.

The reason why it is so difficult to control the fungi is that they were first introduced to Europe from America in the middle of the last century. The traditional European grape varieties were unable to develop resistance to these fungi and there were no resistance genes present in their gene pool. Many attempts to cross traditional European grape varieties with fungus-resistant American ones met with little success: fungal resistance was generally obtained at the expense of wine quality.

After many years new, fungus-resistant grape varieties such as Regent (red wine) and Phoenix (white wine) have been successfully bred using classical methods, but there has been no success with traditional varieties such as Riesling, Merlot or Chardonnay.

It is hoped that genetic engineering will offer new opportunities. Several working groups throughout the world are looking at ways to transfer specific genes which will make even the traditional grape varieties so popular with wine drinkers resistant to harmful fungi. For instance trials are being conducted on genes found in barley. When inserted into grapevines, these genes cause the vines to produce the enzyme chitinase, which breaks down the fungal cell walls. Other strategies use genes which attack the metabolism of the fungus and block it.

Trials in Franken and the Pfalz

Tests will be conducted to see if the grapevines bred in the laboratory also show the desired effect in the vineyard and resist attack by mildew and grey mould. The insertion of the novel gene into the grapevine should not, however, affect the quality of the wine. Grapes from the genetically modified vines will be harvested and turned into wine. For comparison, identical grapevines without the chitinase gene will be grown on an adjacent plot and also made into wine. These wines, however, will not be for sale. If the transgenic grapevines live up to their breeders’ expectations, further trials will follow. But consumers will have to wait at least 20 years before they can expect to see a fungus-resistant Riesling on the market.

Those responsible for the deliberate release have given assurances that there is no need to worry about a risk to the environment caused, for example, by pollen transfer. If neighbouring grapevines were to be pollinated with pollen from the transgenic Riesling, the extra gene would only be present in the grape pip. In winemaking only the flesh of the fruit is used.

Genetically modified grapevines - a global perspective The development of genetically modified grapevines is already further advanced in other countries than in Germany. Research institutes in France, the USA, Canada and Australia are leading the way. There are also working groups in Israel, Japan, Spain and South Africa. The objectives are to confer resistance to various fungi, plant viruses and diseases and also to increase tolerance to low temperatures. In Canada attempts are being made to insert specific genes into grape varieties to facilitate winegrowing in colder climates.

However, scientists are unable to predict when the first wines from transgenic grapevines will be ready to sample. Estimates range from five to fifteen years. Even in the USA many wine companies remain reticent. There is widespread scepticism as to whether the foreign genes inserted in the grapevines will indeed have no impact on the taste and quality of the wine.