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The Right Chemistry: When American roots saved the French wine industry

Aphids were causing considerable damage and various attempts to solve the problem were unsuccessful, until two winemakers had an idea.

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It seems the toads and chickens didn’t have much of an appetite for aphids, the tiny insects that suck the nutrient-rich sap out of plants and are the bane of horticulturalists. When phylloxera vastatrix, a species of aphid, infested French vineyards in the latter part of the 19th century, some desperate vintners positioned toads under the vines, hoping the creatures would dine on the little bugs that threatened to destroy the wine industry. Others allowed chickens to roam through the vineyard thinking they would peck away at the insects. Neither approach worked. The insects also defied the pesticides available at the time. Finally, French winemakers Leo Laliman and Gaston Bazille found a solution to the phylloxera infestation and put French wines back on French tables, to the relief of the population.

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Laliman and Bazille were familiar with accounts of the failure of French colonists in America to grow grape vines they had brought from Europe. The colonists did not know why the vines failed to thrive, but noted that there was no problem growing native American grapes, and switched to these, albeit unhappily, because they thought French grapes produced better wines. A possible explanation for the failure of the French vines to grow in America arose in 1870 when American entomologist Charles Valentine Riley confirmed that phylloxera destroyed the roots of vines by injecting a venom that allowed them to feast on the sap. Could it be that American rootstock had evolved resistance to the insect’s venom, but French vines had not, since the phylloxera aphids were not native to Europe? Laliman and Bazille now had an idea. Import American rootstock and graft shoots of French vines onto them. That worked! The shoots grew and developed into vines that produced the desired grapes. While American roots saved the French wine industry, there was some poetic justice here since it was the importing of American plants that accidentally introduced phylloxera to Europe in the first place.

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Phylloxera was not the only problem introduced by American botanical specimens. Various fungi capable of causing plant diseases also made their way across the ocean. One of these was “downy mildew,” a fungus that stunts the growth of plants. The Bordeaux region of France was particularly affected, and vintners sought help from University of Bordeaux botany professor Pierre-Marie-Alexis Millardet. As he walked through the vineyards, the professor made an interesting discovery. Vines that bordered the property close to roads showed no mildew, while other vines were affected. Upon questioning the growers, he learned that they had a problem with passers-by helping themselves to the grapes. The losses were significant enough to take action, which they did by spraying the vines with a mixture of copper sulphate and lime (calcium hydroxide). This results in a precipitate of copper hydroxide that imparts a bitter taste to the grapes and also has an unappetizing green colour. Millardet wondered if this was also the reason for the lack of mildew on these plants. Trials with this combination of chemicals soon revealed that they prevented fungal spores from germinating, and that spraying with this “Bordeaux mixture” pre-empted the fungal disease. French palates were mightily grateful for Millardet’s investigations of vintners’ efforts to deter grape thieves.

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Not all fungi are detested by winemakers. “Botrytis cinereal,” better known as “noble rot” is welcomed by producers of dessert wines such as Sauternes from Bordeaux, some Rieslings from Germany, and perhaps most famously, Tokaji Aszu from Hungary. Grapes infected with this fungus dehydrate and shrivel, meaning that about a kilo of grapes is needed to yield a few millilitres of juice. Since the fungus does not affect the sugar content, the resulting wine is very sweet. But it is not only the sweetness that is prized, it is the flavour that the fungus contributes, some of which is attributed to compounds such as phenylacetaldehyde produced by the fungus.

Botrytis requires very special weather and soil conditions to thrive, and furthermore, since not every grape is affected, the shrivelled ones have to be hand-picked. Because of such factors, botrytized wines are expensive, with one of these, a particular vintage of Essencia from the Tokaj region of Hungary that is fermented for some eight years, being the most expensive wine in the world. It retails for an astounding $40,000 a bottle! This gem is to be sampled by oenophiles only a spoonful at a time, and according to some, on one’s knees, so that appropriate homage is rendered to its incredible quality which is said to be maintained for 200 years. Maybe around the year 2200, some clever columnist will be able to comment on this being put to a test.

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Although I have not been privy to this holy experience, I have visited Tokaj, and have sampled the less exalted but still world-famous Tokaji Aszu, also made with nobly rotten grapes, said to have been called the wine of kings and the king of wines by none other than Louis XIV. To be honest, that is not why I was drawn to sample a bottle in Tokay. It was because Sherlock Holmes once offered a glass to Watson, saying, “A remarkable wine, Watson. I’m assured that it is from Franz Joseph’s special cellar at the Schonbrunn Palace.” If Holmes recommended it, that was good enough for me! As if that weren’t enough motivation, I also knew that in the book, The Phantom of the Opera, the Phantom offers Christine a glass of Tokay on her visit to his lair below the Paris Opera.

And how did the Tokaji Aszu taste? I can say it was a delightful complement to the veal paprikash and langos we were served. Blessed be the fungus!

joe.schwarcz@mcgill.ca

Joe Schwarcz is director of McGill University’s Office for Science & Society (mcgill.ca/oss). He hosts The Dr. Joe Show on CJAD Radio 800 AM every Sunday from 3 to 4 p.m.

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