Not met a PIWI yet? Nor had I, till just recently. The name cropped up at Wädenswil, the Swiss viticultural research station whose vineyards and original home are pictured above, on the southern shore of Lake Zurich, which I visited in the context of the end-of-summer Mémoire & Friends event. I learnt that PIWI (pronounced pee-vee) is an acronym for Pilzwiderstandsfähige Rebsorten (you have to love the way the German language builds these dazzling composite words), aka fungus-resistant grape varieties. Since then, I get the feeling everyone’s talking about them – or maybe it’s just what happens when you meet a new term/word/phenomenon, and then you can’t stop hearing it at every turn.
So what’s the story and why are such grape varieties the subject of intensive research programmes in a number of different countries? Vines, in common with any other plant grown in vast monocultures, are susceptible to all kinds of diseases. The principal enemies for winegrowers are that dreaded duo, powdery and downy mildew (there are plenty more, but let’s start with these). When these two stage an attack on the vine, the leaves turn mealy, break out in a rash of brown or black spots and fall off. The grapes get a dusty bloom and shrivel up miserably. Treatments to ward off these attacks, according to the PIWI International website, can be necessary anything from 6 to 18 times during the growing season, depending on the year (2016 was a particular horror, with its cool, damp conditions).
In conventional viticulture, the treatment will be with synthetic chemicals. Organic winegrowers will spray the plants with ‘natural’ chemicals such as copper sulphate (aka Bordeaux mixture or bouillie bordelaise) and sulphur. But the damage done to the environment by using chemicals (whether synthetic or natural) has prompted researchers to look for alternatives – enter PIWIs. The point about these newly created varieties is that they have in-bred resistance to these troublesome, crop-reducing fungi, thereby eliminating the need to treat at all.
At Wädenswil, Michael Gölles, who is responsible for their experimental vineyards, showed us these two rows of Müller-Thurgau vines growing side by side. In the lefthand picture, the vines were left untreated during the whole season and are suffering from a nasty dose of downy mildew, with a dusting of the powdery kind. On the right, the vines had received 7 different applications with several synthetic fungicides permitted within the Swiss IP standard (= Integrated Production, or a sort of halfway house towards organic), designed to combat powdery and downy mildew as well as botrytis.
Quite a good illustration of why it’s necessary to treat grapevines – or better still to try and breed varieties that don’t get the diseases in the first place.
What are PIWIs?
The earliest kinds were created by crossing European grape varieties (Vitis vinifera) and American fungus-resistant varietals (Vitis labrusca or riparia). One of my biggest surprises was to learn that they’re nothing new: these hybrids were used in France from the 1880s onwards in a frantic response to the plague of downy and powdery mildew which preceded the dreaded phylloxera, which in turn finished off almost all the European vineyards. The aim then (as now) was to combine the resistance to diseases and phylloxera of the American grape varieties with the superior quality of European varietals. Unfortunately, while this generation of hybrids (they have names like Isabella, Concord, Delaware & Co.) scored on the disease-resistance front, they fell down on quality, producing wines that are almost universally despised for their unpleasant, so-called ‘foxy’ aromas and flavours.
Today there’s a whole new generation of PIWIs, the result of decades of crossings created since the 1950s, some of which are showing real promise. It’s these modern kinds that are being trialled by Agroscope, the Swiss agricultural research centre, at various sites around the country including Wädenswil. Germany, Austria, Central Europe and Scandinavia are also active in the field. Somewhat surprisingly, given that PIWIs were first used there, France seems less enthusiastic and the few winegrowers I’ve spoken to on the subject remain deeply sceptical. In an email, José Vouillamoz, the noted botanist and grape geneticist who co-authored Wine Grapes, told me that “PiWis are a niche market, most favored by environment-conscious producers and consumers. Their current surfaces are still anecdotal in Germany or Switzerland, but they are on the rise along with the organic boom in the whole [of] Europe. They will probably never supplant the traditional vinifera, but they will become more and more important.” (Note that PIWIs are created by crossing different varieties; they are not GMOs.)
And the taste test?
The environmental benefits of PIWIs are not in doubt. The key question will be: how well do they stack up on the taste front? At Wädenswil, we tasted Muscaris, a white variety created in Freiburg (Germany) by crossing Solaris (another modern PIWI) and Muscat – I liked its grapey Muscat aromas and flavours braced by good acidity. Then later in the month at the Cave de la Côte with their talented and innovative winemaker Rodrigo Banto, I bumped into a red PIWI named Divico, this one a cross between Gamaret and Bronner, which is dense, purplish-red with rich red fruit aromas (and not even a hint of a fox). (Galotta, on the right, is a Swiss cross between Gamay and Ancelotta, but not a PIWI.)
Finally, and right on cue, a random email plopped into my Inbox a few days ago proclaiming that “2016 was the year of PIWIs!” It describes PIWI International’s recently staged Wine Awards (now in their 7th year), hails 2016 (that horror year, remember?) as “the perfect one to demonstrate the brilliance of these fungus-resistant varieties”, and lists the prizewinning wines and their makers. If you’re anywhere near Stuttgart on 18th November 2017 and would like to put some to the taste test, there’s an event (open to the public) entitled “Weinkost Weinstadt” in the Jahnhalle, which will provide “the perfect opportunity to learn more about the quality and diversity of PIWI wines” (www.weinkost-weinstadt.de).
PIWIs are definitely having a moment…coming soon to a vineyard near you.