A Common Ingredient in Fine Wines That May Surprise You

St. Paul, Minn. (January 29, 2003)—It may not be romantic but it’s still sweet. Many of the best and priciest wines likely to be enjoyed over candlelit dinners this Valentine’s Day get their remarkable flavor from a common rot fungus. That’s right. Are your grapes full of fuzzy mold? Don’t throw them out. Make wine out of them. At least that’s what makers of some of the world’s most exceptional wines do. And while you might find this odd, think of how plant disease scientists must feel. Normally called upon to combat such diseases, in this case they’re actually called upon to help create them.

“We supply the fungus,” says Walter D. Gubler, a plant pathologist with the University of California, when asked about the role of plant disease scientists in helping to create infected grapes for winemaking. “Many growers actually try to induce Botrytis toward the end of the growing season. That’s how valued this process is.”

Gubler says that while scientists have the ability to infect wine grapes with the Botrytis fungus, they still need the cooperation of Mother Nature to make it happen on a scale needed for wine making. “The weather conditions have to be just right to set this process in action,” says Gubler, “humid, cool nights; dry, sunny days; humid soils.” And that’s the part that scientists can’t control.

But on the relatively rare occasions when it all comes together and the Botrytis fungus is able to take hold, it creates what is called "noble rot." As the noble rot progresses, the grapes shrivel up, concentrating the sugars and tannins and imparting a distinctive flavor from the fungus. These “noble rotted” grapes are then used to make a variety of special types of wines, particularly dessert wines (Golden Sauternes) and others, including Riesling, Semillon, and Sauvingnon Blanc, all of which are referred to as “botryised wines.”

“This is one of those unusual cases in which a plant disease is actually considered beneficial,” says Gubler. “Usually scientists like myself work with growers to rid crops of disease, not join them in wishing for their occurrence.”

So this Valentines Day, as you order up your favorite Sauvingnon Blanc, you might want to give a toast not only to the winemakers, but also to the plant disease scientists who helped bring that sweet “fruit of the Gods” to your table. “I have to say,” says Gubler, “that this work is highly pleasurable.”

The American Phytopathological Society (APS) is a nonprofit, professional scientific organization dedicated to the study and control of plant disease with 5,000 members worldwide.