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Missouri wine grape might be answer to fighting mildew and rot

Tuesday, December 14, 2010 | 7:20 p.m. CST

COLUMBIA — Five years ago, Les Bourgeois Winery in Rocheport lost 25 percent of its vignoles crop to downy mildew and late season rot.

The winery has since taken steps to prevent such losses, but record levels of precipitation in recent years have increased the threat from mildew for vineyards in the area.

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"The three past years have been some of the most difficult growing seasons," said Cory Bomgaars, head winemaker at Les Bourgeois.

Losing crops isn't the only damage attributed to downy mildew and other types of fungi, he said.

"The wine quality can even be affected," Bomgaars said. "It might turn a $10 gallon into a $5 gallon."

To combat mildew, vineyards will often spray fungicides on their crops, but one local varietal has a natural resistance to downy mildew and other diseases that plague susceptible European varietals.

The Norton grape is a 150-year-old hybrid from a natural vine growing in America that has learned how to cope with downy mildew, powdery mildew and black rot fungus. It can ramp up its defenses to prevent the fungus from establishing itself.

Researchers are now trying to identify the specific genes responsible for Norton's resistance and hope to cross breed these genes with other grape varietals.

At MU, Walter Gassmann is looking specifically at how to identify and incorporate valuable Norton genes, then transfer them into other varietals that make both red and white wine.

"It is very rare to have plants that are resistant to a broad range of pathogen classes," said Gassmann, researcher in the Bond of Life Sciences Center and associate professor of plant sciences in the College of Agriculture, Food and Natural Resources.

As a preliminary step, he has successfully added Norton's resistant genes to Arabidopsis, a plant less complex than grapes.

Using the results of Gassmann's genetic mutation, researchers at Missouri State University crossbred hybrids of cabernet sauvignon and Norton in hopes of transferring Norton's resistant genes.

Because this is a difficult process, he said it could be at least 10 years before new hybrids go into commercial production.

"Right now, crossbreeding is the only acceptable form of incorporating the desired trait from Norton into other grape species," Gassmann said.

Because the public will not accept genetically mutated organisms, he cannot replicate the process he uses with Arabidopsis on the actual grape vines.

"I believe the lack of public acceptance has a lot to do with misinformation and scare tactics," he said.

If the researchers are successful in creating resistant hybrids, Gassmann said, they hope to eliminate or reduce the use of fungicides. This would allow the grapes to grow where it is now climatically unfeasible without fungicides.

Using vines with Norton's resistance would also improve the yield of existing crops and eliminate the cost of fungicides.

But even Norton has its limitations, winemakers say.

Said Dave Johnson, the head winemaker at Stone Hill Winery in Hermann: "Norton in some years can be grown without fungicide, but in a wet year, even Norton needs a little help."


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