PIWI (pronounced pee-vee) is an acronym that plunders the first two syllables of the German name Pilzwiderstandsfähige Rebsorten, meaning “fungus- (or disease-) resistant grape varieties”.
The earliest kinds were hybrids created by crossing European grape varieties (Vitis vinifera) and American fungus-resistant varietals (Vitis labrusca or riparia). They were used in France from the 1880s onwards in a frantic response to the plague of downy and powdery mildew which preceded phylloxera, which in turn laid waste to almost all the European vineyards. The aim then (as now) was to combine the resistance of the American grape varieties to diseases and to phylloxera with the superior quality of European varietals. Unfortunately, while this early 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. Some of these modern kinds are being trialled by Agroscope, the Swiss agricultural research centre, at various sites around the country including Wädenswil on Lake Zurich. Others are being trialled by the private vine breeder, Valentin Blattner. Germany, Austria, Central Europe and Scandinavia are also active in the field. Somewhat surprisingly, given that PIWIs were first used there, France has been slower to embrace this new generation of interspecific hybrids. Dr José Vouillamoz, the noted botanist and grape geneticist who co-authored Wine Grapes, notes that “PiWis are a niche market, most favoured 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.)
So what’s the story and why are such grape varieties the subject of intensive research programmes in several 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 dread 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 from 6 to 18 times during the growing season, depending on the year.
In conventional viticulture, the treatment will be with synthetic chemicals. Organic winegrowers may spray the vines with “natural” chemicals, which include copper 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 value of 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.