Scientists Isolate Genetic Difference Between European and American Vines

With "foxy flavor" gene identified, breeding could create new hybrid varieties
Oct 19, 2009

Despite being a compliment for people, "foxy" is quite the insult for a wine. It means a wine is musty or smells like wet fur, and it's an infamous characteristic in wines made from American grape varieties such as Concord.

But as reported in a new study, German scientists have discovered a gene that could enable selective breeding to eliminate the foxy flavor, setting the stage for hybrids that are as disease and pest-resistant as American vines but produce wines as pure and beautiful as European vines. Their discovery also reveals a bit of the vine's long genetic history.

"Now that we can identify the source of the off taste, we can use a hybrid of the American and European varieties and silence the gene for the off flavor," said study co-author Wilfried Schwab, a professor of biomolecular food technology at the Technical University of Munich. "We [could breed] a grape with the original flavor of the European grape but the resistance of the American grape."

Such breeding could be important because European vines, Vitis vinifera, are vulnerable to American diseases and pests. In the 19th century, several of these killers were accidentally transported to Europe on American vine cuttings. The fungal diseases oidium and downey mildew, and the root aphid phylloxera devastated European vines. To prevent phylloxera, grapegrowers now graft European vines onto American rootstocks, and to fight fungal diseases, extensive chemical spraying is needed. Breeders have tried crossing American and European varieties to create hybrids that offer both resistance and flavor, but have had mixed success.

Schwab and his colleagues were investigating a pigment mutation, but found a genetic fork in vine history. Thanks to a double mutation, European vines don't produce all the same pigment chemicals American vines do. Writing in the Journal of Agricultural and Food Chemistry, Schwab and his colleagues describe how this mutated gene happens to lay adjacent the gene responsible for foxy flavors on the North American grape chromosome. This proximity means that crossbred vines that lack the pigment gene will also lack the foxy flavor gene, thus proving a new and easier way to identify the resistant and theoretically tastier crosses.

Breeding hybrids is a grueling, time-consuming process that involves making crosses, allowing vines to mature and then testing the wines. By providing a chemical marker, this enzyme could speed up the breeding process. That could profoundly alter the industry. According to M. Andrew Walker, a professor of genetics in the department of viticulture and enology agricultural at the University of California at Davis, pesticides constitute the main expense of most vineyards. "Huge, huge amounts of money," said Walker, who wasn't involved in the study. "The main cost for a vineyard is controlling mildew. Every two weeks they spray for mildew. [Natural immunity] will save growers a lot of money, and it will save the environment."

But Schwab's co-author on the paper, Reinhard Toepfer, does not share his optimism. Toepfer, who heads the Institute for Grape Vine Breeding at the Julius Kühn Institute in Geilweilerhof, Germany, thinks that scientists like Schwab oversimplify the problem. "Its not easy to select for all the right qualities," said Toepfer. "More than flavor, crosses have breeding yield, weather resistance, body. No one knows the genes for wine body." Some hybrids have already been developed that lack the foxy flavor, including Seyval Blanc, but they have not proved popular.

There's another road block: A single gene change, whether through breeding or direct genetic manipulation, robs a grape of the right to carry a famous varietal name like Cabernet Sauvignon or Chardonnay. The hurdle of marketing new varieties might be the biggest challenge of all.

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