Fruit and Vegetables Grapes and Wine

In the middle of the 19th century, many new fungal diseases appeared in Europe. Traditional vine varieties became particularly vulnerable to these new diseases. Genetic engineering offers some new possibilities for developing disease resistant varieties. Immediate success, however, is unrealistic.

Fungal diseases like grey mould, powdery mildew, and downy mildew are major problems in many of Europe's wine regions. They not only cause losses in yield, they also reduce wine quality. Cloudy and persistent fungal residues are a serious problem in the wine cellar.

The intensive use of fungicides is still common in many vineyards. When infection is widespread, winegrowers may spray up to eight times per year. Even organic farmers can't forgo treatments against fungal disease. They often spray with copper solutions, which pollute soil with heavy metals. Newer, but less effective methods include clay preparations and plant extracts.

Young, genetically modified grapevines in a greenhouse. Plant breeders have not yet been able to produce fungus resistant version of traditional vine varieties. Genetic engineering could open up new opportunities. Photos: www.biosicherheit.de

Riesling, Merlot and Chardonnay: Delicate vine varieties Europe's traditional vine varieties are especially susceptible to fungal diseases. Because these new fungal pathogens were introduced to Europe from America in the 19th century, European vines never were able to develop resistance. Many attempts to cross Europe's varieties with resistant varieties from America have had little success: disease resistance always compromised quality. Although years of breeding have resulted in the development of new, fungus resistant vine varieties, modern breeding has not yet been able to provide fungus resistant versions of favourites like Riesling, Merlot, or Chardonnay. Genetic engineering has brought new hope. Worldwide, several teams are working on transferring resistance genes into traditional vine varieties. Specifically transferring only the genes necessary for disease resistance would leave the vine's other traits virtually untouched. This would retain the original character of the wine, which would not be possible using traditional breeding methods. If scientists succeed in developing fungus resistant vine varieties with genetic engineering, it would take years until any wine from these varieties would be available on the market.

Scientists have identified several substances in barley that protect it against fungal pathogens. Transferring the genes that enable the production of these substances could protect vine varieties from pathogenic fungi.

• Chitinase (enzyme) genes have been transmitted in this way. Chitinase digests chitin - a substance found in fungal cells.

• Other strategies take advantage of genes coding for proteins that disrupt fungal metabolism (glucanase or ribosome-inhibiting proteins)

It is not yet known if these strategies will be successful. There have been some promising successes, but also several setbacks. Field trials conducted in Germany between 1999 and 2004 found that new, transgenic vines were just as susceptible to disease as conventionally bred varieties.

See also on GMO-Compass:

• Disease Resistant Crops