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By Phillip Reedman MW

Reading Time: 4 min 9 sec

1847 marks a notable year in viticulture; for that is when European vineyards first came under attack from a pest originating on the other side of the world.  We all know about Phylloxera, but that’s not what we’re talking about here; rather, we’re talking about the mighty, if microscopic, Erysiphe necator, aka powdery mildew.  As if one exotic pest wasn’t enough a second arrived in 1878 in the form of Plasmopara viticola, better known as downy mildew.   The life of vignerons changed forever.

A solution was rapidly found to combat Phylloxera.  Growers grafted European vines, Vitis vinifera, onto rootstocks bred from American vines, which, having evolved alongside the pest, had developed resistance to it.  But these two American mildews remain an annual battle for vignerons around the world.

We are all trying to reduce our carbon impact on the planet to minimise climate change.  One way of reducing our carbon impact is for grape growers to spend less time on their tractors spraying fungicides to stop these mildews in their tracks…failure to stop them results in crop loss and an even bigger problem the next year. 

Organic viticulture is one of the ways in which tractor and spray use can be reduced.  Organic management works better in some climates than in others. Sadly, the Venn diagram of climates suitable for organic cultivation and viticulture isn’t quite as satisfactory as you’d wish.  Even where the two do intersect, it often means that other valuable natural resources, particularly water, are being used to grow wine rather than food or to be used, as nature intended, for the maintenance of the river’s ecosystems. It’s a hard equation to balance; that much is certain.

The solution to Phylloxera turned out, after some experimentation, to be a biological one.  Is there a similar biological solution to mildews?  Well, it looks as though there might be, though it is a roundabout route to get there. American vines, which provide the essential rootstocks onto which we graft European vines, might be a solution if we simply grew them and harvested their grapes.  After all, American vines are much more resistant to mildew.  Sadly, American vines do not make great wine, and while some people enjoy the wines or jellies they make, most people find the ‘foxy’ taste they bring unpleasant. 

So, if we can’t harvest the grapes of American vines and make wine, can we harvest the attributes we do want from the vines some other way?  Enter the vine breeder, scientists who pollinate one vine’s flowers with the pollen of a different species and grow the plants which result from this crossing.  It is not a fast process; allow about 30 years from start to finish. 

By using this painstaking but long-established method of breeding new plants and selecting those new vines which show the most mildew resistance, breeders have developed the so-called PIWI vines. PIWI is a contraction of the German for fungal resistant.  Once a vine has shown good resistance to mildew, the only other question is, ‘Does it make good wine?’  The answer for many, but by no means all, of these new varieties is “yes.” 

PIWI vines have been adopted in many wine-growing regions of Europe. Germany, where much of the plant breeding work was done, has seen enthusiastic take-up of these varieties.  Austria, France, Italy, the Czech Republic and Switzerland are all on board too.  Those less well-known wine-producing countries: England, Belgium, Poland and Sweden have each planted vineyards with PIWIs.  At the 2022 PIWI International Wine Challenge, 185 wines were entered for blind tasting, the majority of them white wines; however, sparkling wines, skin-contacted ‘amber wines’ and a significant number of red wines were entered too.  The word is spreading, and the wines are reaching international markets.

So, how will you know that the wine you are looking at is a PIWI variety? Well, the bottle might be labelled with the PIWI logo, but most likely, the variety stated on the label will be one which you sort of half recognise or perhaps don’t recognise at all.  Owing to their origins based in classic European varieties, many PIWIs are named in honour of their parent variety; thus, we have Cabernet blanc, Cabernet jura, Pinot nova and Donnaurisling….hence you half recognise the name.  Other variety names are more obscure and are names which might become familiar in coming years.  Look out for the likes of Regent, Rathay, Roesle and Vidoc.

Many growers of PIWI varieties farm organically: they are capitalising on the greater fungal resistant characteristics of PIWIs to minimise spray regimes and thereby reduce the environmental impact of grape growing.  Other growers are using PIWIs to overcome the challenges of a rapidly changing climate, one where unpredictable rainfall patterns during the growing season make viticulture increasingly difficult.  The route to sustainability has many elements; without doubt, PIWIs are one of them.