COLMAR, FRANCE-French scientist Jean Masson carefully unlocks the gate of a heavily protected open-air enclosure. Behind the fence and security cameras there are no wild animals or convicts, just 70 vines.

In the heart of the picturesque Alsace wine region, researchers have planted France's only genetically modified vines in the hope of finding a way to battle the damaging "court-noue" virus afflicting a third of the country's vines.

The modified plants will not grow grapes or yield any wine, and scientists at the state-financed National Institute for Agricultural Research (INRA), which is conducting the experiment, say it is safe.

"The environmental risk is nil," said Masson, head of INRA in the eastern town of Colmar. "We have taken all safety measures."

But many local winegrowers fear the plants will contaminate their vineyards and ruin the reputation of France's wine sector.

"It makes me angry because this is imposed on everyone without us being informed about the risk," Pierre-Paul Humbrecht, a maker of bio wines, said in his vineyard just a few km away from the open-air experiment.

"If there's a problem, it concerns us all. We fear for our vines."

In France, resistance against genetically modified food is fierce. Farmer and environmentalist Jose Bove has shot to national fame for ripping up modified crops.

INRA stopped its first tests on genetically modified vines in the Champagne region in 1999 following protests. After years of talks with locals and winemakers, Masson said his researchers had now set up enough safety measures to satisfy critics.

They dug a hole of the size of a basketball court, put in a cover to shield the natural ground and planted the contested vines on soil from outside. The plants are also surrounded by some 1,500 normal vines.

The prison-style fence was a request by environmentalists, who wanted to prevent animals and human intruders from carrying parts of the plants outside the enclosure, Masson said.

Damaging virus

Masson said INRA conducted tests only in the lower part of the vine, the rootstock, which did not carry any grapes.

Almost all French winegrowers have used separate rootstocks since the phylloxera pest nearly wiped out the European wine industry in the late 1800s.

In response to the tiny louse, which attacks the root system of vines and was accidentally brought to Europe from America in 1860, European winemakers imported resistant American rootstocks and grafted their vines onto them.

INRA says no genetic information can pass from this rootstock into the plant's upper part -- which grows the grapes. But to ease fears that a modified plant could one day yield wine, the researchers will strip the vine of any blossoms.

"We don't want to produce grapes. We want to answer the scientific question of whether this transgenic (genetically modified) root can lead to the plant developing durable resistance to this virus," said INRA's Olivier Lemaire, who is in charge of the project.

Winemakers agree the court-noue virus is causing havoc but they disagree over whether INRA's research is needed.

"In the long-term it is a very dangerous virus," said 80-year-old wine grower Jean Hugel, whose family has run a vineyard in the small town of Riquewihr for more than 300 years.

"The end result is that the blossoming doesn't go well and you don't have any crop."

So far, winemakers have had to battle the virus with very toxic pesticides or by letting the soil rest for years.

"If they find a way to get rid of the virus on the American root, with assurances that it does not pass into the European grafted-on vine, it would be a great, great success. You have to try," Hugel said.

But fellow winemaker Frederic Geschickt, bringing in grapes from his vineyard, said he would rather live with the virus than accept the danger of genetically modified plants.

"You should tear these vines down," he said. Genetic tests on vines already exist in places such as the United States but the French case was special, he said.

"French wines are already subject to strong market pressure. Over recent years, competition from New World wines has grown. The only solution for French wines is to affirm their particularity and their difference," he said.

Genetic tests risked making French wines uniform, he said.

New world threat

The wine sector -- a pillar of French life that provides 75,000 jobs -- has been hit hard by competition from "New World" rivals such as Australia and Chile.

France and Italy are the world's top winemakers with the former accounting for around one fifth of world production, but New World countries have been increasing their market share.

Masson said the scientists did not want to market their test results, pointing out that scientific publication would be the ultimate goal when the experiment ends in four years time.

But environmentalists fear the case sets a precedent.

"They want to test to what extent we will resist this," said Henri Stoll, Green Party mayor in the small town of Kaysersberg which is surrounded by vineyards.

"If we don't, something else will come up. We will have genetically modified wine and a genetically modified society."

But the grey-haired Hugel said he believed winemakers were too intelligent to ever make genetically modified wine.

"One hundred percent of a wine's quality is in the grapes," he said. "We have not seen any miracles in 370 years."