Monday, November 5, 2018

How many grape clones are there per variety?

I recently noted that the twin ideas of "varieties" and "clones" are basic to grape-growing, whether they are used for wine-making, table grapes, raisins, juice, jelly, canning, or rootstocks (Grape clones and varieties are not always what they seem). This leads me to ask the question posed in the title.

Illustration By Keith Ward

The number of clones is often related to the genetic mutation rate of the variety. Pinot noir is therefore recognized as one of the most mutable grape varieties. Indeed, it is so mutable that we have produced several different clones that we actually treat as being varieties, because they can be used to make very different wines (as discussed in the previous post). Indeed, Pinot noir itself also has more recognized clones than do most other varieties.

This is illustrated in the first graph. The data come from the list of varieties and clones currently approved for viticulture in France (Catalogue of vines grown in France). Each grape variety is listed horizontally, with the number of approved clones counted vertically. Only the 38 varieties with at least seven clones are shown — there are a total of 269 approved varieties, and 950 clones, although 161 of the varieties (60%) have only one listed clone.

Number of clones per grape variety approved in France

As you can see, Pinot noir is way out in front. Its history is, of course, associated specifically with Burgundy, although it is now an international variety. It is therefore interesting to note that the second variety in the graph is Gamay, the red-wine grape from Burgundy's nearest neighbor, Beaujolais. The people of this part of France have had a long time to keep an eye out for potentially useful mutants among their vines.

We can, of course, separate the graph into both red- and white-wine grapes, and this is illustrated in the next graph, which shows the 30 varieties of each type with the most clones. It is immediately obvious that red-wine varieties tend to have more clones than do white-wine varieties. Presumably, this reflects the historically greater interest that has generally been shown in producing "fine" red wines compared to white wines.

Number of clones per red and white grape variety approved in France

As usual in this blog, we can search for simple patterns among these data. Mathematically, the data from the first graph most closely fits a Power model, as shown in the following graph, where the added line shows the model. The most obvious place the model does not fit the data is the first two varieties — both Pinot noir and Gamay actually have fewer clones than "expected" from the model!

If we fit the Power model to the red and white varieties separately, as shown in the next graph, then it is interesting to note that the model fits the white varieties very well, although the first white-wine grape (Chasselas) has too few clones. However, the model fits the red-wine varieties rather more poorly, and especially Pinot noir and Gamay have many too few clones for this model . The latter results from the greater number of clones for the remaining red varieties — red-wine grapes generally have more clones than we would "expect" from a simple mathematical model.

So, we may conclude that white grape varieties have clone numbers that fit a simple mathematical model, but red varieties have more clones than can be "explained" by any such model. This is likely to be because red wines have been preferred by consumers, so that the vignerons have been more keen to find "better" clones for lots of the red varieties but only a few of the white varieties.

Some comments

Lest anyone thinks that there is some restriction on the number of grape varieties that can be used in France, it is important to note that new varieties are being approved all the time (eg. for 2018: New grape varieties in France, some forgotten, some hybrids). The matter of hybrids is of particular interest, because they have long been detested in France but are now being seriously considered as a solution to viticultural problems like downy mildew (see French wine's hybrid dilemma).

However, the situation in France is quite formal:
Grapevine clonal material in France is subjected to extensive testing and certification under the aegis of the Ministry of Agriculture. The Institut Français de la Vigne et du Vin (IFV) is a national agency certified to manage and coordinate the French national clonal selection program. The responsibilities now entrusted to the IFV were formerly performed by an entity known as the Etablissement National Technique pour l’Amelioration de la Viticulture (ENTAV), and include maintenance of the French national repository of accredited clones, and administration of the ENTAV-INRA authorized clone trademark to protect the official French clones internationally.
The list of approved French cultivars is important, because only cultivars from this list can be used in wines given legal protection under the Appellation d'Origine Contrôlée (AOC) scheme administered by the Institut National de l'Origine et de la Qualité (previously INAO). Recently, INAO has allowed other varieties from the list to be used in AOC wines as "grape varieties for climate and environmental adaptation", which means that issues such as climate change can be addressed by trialling new varieties.

There has been some concern expressed about restricted use of clones in many vineyards, especially outside Europe (eg. Genetic instability and how it affects wine). In the past, vineyards tended to be a mosaic of clones, but modern agriculture (not just for grapevines) has shown a strong move towards using single clones — those that are seen as being "the best" in some ineffable way. For example, Cabernet sauvignon clones 07 and 08 have been the basis of many of the California Cabernet vineyards for decades (see The guide to wine grape clones).

However, this approach is asking for trouble — when problems occur in the field they are likely to affect all of the plants at the same time, because the clones are genetically identical. Resilience to the vagaries of different seasons (especially weather, pests) is based on diversity, not lack of it. As has been noted (Myles et al., Proceedings of the National Academy of Sciences of the USA 108:3530-3535):
Vegetative propagation [has] discouraged the generation of unique cultivars through crosses. The grape currently faces severe pathogen pressures, and the long-term sustainability of the grape and wine industries will rely on the exploitation of the grape’s tremendous natural genetic diversity.
To this end, of the known varieties, 7,200 are grown at the Centre de Ressources Biologiques de la Vigne (CRB-Vigne) de Vassal-Montpellier, near the town of Marseillan in southern France.

Perhaps at issue here for the growers is that some clones will produce mediocre wines when grown in certain regions but not others. For example, it has been noted that the original Chardonnay clones used in Oregon came from California, where the climate is warmer and drier, and that this situation was much improved when clones were imported directly from Dijon in Burgundy, where the climate is more similar (see The role of grape clones in planting grapes)

Also, there is the matter of intellectual property rights — the use of some clones requires the payment of royalties (see How wine clones are already taking over). The Foundation Plant Services Grape Registry currently lists 594 grape varieties used for all purposes in the USA, which is more than in France, but many of these are proprietary. The latter do include, of course, the ENTAV-INRA authorized clones.


  1. Here's one subject the French government and French winemakers are more than happy to concede the Yanks are better at.

    From The New York Times Online
    (September 25, 2004):

    “Winemakers Protect Outlawed Vines: The Grapes of Wrath”


    By Thomas Fuller

    The wine produced in this remote valley of southern France is dark crimson, somewhat fruity -- and illegal. For at least three generations, local families have tended to the gnarled vines that grow from rocky terraces above the Beaume River. The wine they make is banned for sale in Europe because it is made from an American grape that was ordered uprooted by the French government 70 years ago.

    Outlawed grapes?

    The story has been all but forgotten in France today except among a handful of wine experts and a gaggle of bureaucrats who enforce the law: The French government banned wine made from American grape varieties on the grounds that it tasted like raspberries and was thus offensive to the palate. The European Commission adopted the French rule in 1979, making it illegal to grow these varieties anywhere in the European Union.

    The percentage of outlawed American grape varieties is relatively small in France. But the offending vines are also sprinkled widely throughout several East and Central European countries that have recently joined or will soon join the European Union.

    "You can't tell the Hungarians, Bulgarians and Romanians to uproot their vines," says Pierre Galet, perhaps the world's leading expert on grape varieties. He believes the ban on American varieties is anachronistic.

    Yet the idea of the supremacy of European grapes appears to have carried over until today.

    When Franz Fischler, Europe's agricultural commissioner, was asked in the European Parliament three years ago why the ban on American varieties was still in place, he cited "gustatory defects," which in plain English means bad taste. He also said the wine from the American grapes contained higher than usual levels of methanol, which is toxic.

    Hervé Garnier, who tends to the vineyards here, disagrees with this taste assessment. Garnier, a roofer by profession, is leading a campaign to lift the ban. He bangs out letters of protest to Paris and the European Commission in Brussels from his old stone farmhouse overlooking the river, an idyllic little corner of France and an unlikely place for challenging Europe's huge farm bureaucracy.

    "We're just a drop of water here compared with total French wine production," Garnier said on a recent sunny day at the farmhouse. "We're not threatening anyone."

    Last year Garnier produced 7,000 bottles of wine, a fraction of the 8 billion bottles produced annually in all of France. But the ban on American grapes is significant, particularly for France, wine experts say, because it is a symbol of the overregulation in Paris and Brussels that is hurting the nation's venerable but tottering €15 billion wine industry.

    Australian wine now outsells French wine in key markets like Britain and the United States, partly because it is better adapted to consumers' tastes, especially in the middle price range.

    French winegrowers must abide by strict rules on what grapes they can use. The rules are meant to ensure quality, but they also stifle innovation, prohibiting winemakers from testing new hybrid varieties and grape combinations, experimentation that is common in the New World.

    Galet, the expert on grape varieties, says it should be up to people to decide for themselves what grapes to grow. "I like dark chocolate and there are people who like milk chocolate," he said.

    "I am for liberty," added Galet, who once served as an adviser to the French government on the complex grape classification system. He said the presence of the American grapes in Eastern Europe meant that Brussels would be forced to reconsider the ban.

    [Click on URL for footnote. ~~ Bob]

    1. Thanks for your comments, Bob.

      I will take issue with one of them: "French winegrowers must abide by strict rules on what grapes they can use." Actually, they can use anything they like, from anywhere. What they cannot do is use any wine name they like. It is the names that are controlled / protected by French law, and if you wish to use a particular wine name then you have to abide by its legal definition. If you grow grapes that are not part of a controlled name then you have to use a new (unprotected) name. The latter happens all the time (eg. the rise of the so-called "Super Tuscan" wines), but is not widespread, in Italy and Span, as well as in France.

  2. The terminology of clones is fraught with difficulty. I accept totally that you use the word in the wine grape sense and do not criticise you for that, but it is more correct to say that if you make a clone of an individual (plant or animal) the two are genetically identical. Strictly-speaking a wine grape "clone" is a mutuation that has been propagated commercially because it is useful. Originally of course the propagation was initially done by wine growers in an ad hoc fashion, but I can only imagine that it came to be commonly called a clone because commercial nurseries literally clone the mutation under carefully controlled conditions - ensuring freedom from viruses that can cause further mutations, and weeding out any obvious further mutations that do occur. So the word "clone" here emphasises that all the mutated plant material is identical.

    You also write "The number of clones is often related to the genetic mutation rate of the variety". That is oft-repeated, and almost by definition there must be some truth in it. But a more recent view is that the number of grape clones is mainly related to the age of the variety. The reason being that there has simply been more time for mutations to occur. Also, the fact that a variety has been around a long time suggests that it has proved its worth, and maybe its mutations have been more likely to become clones. Perhaps you might be interested in checking the truth of that idea in a future blog post? I think the main problem would be getting reliable estimates of age - and ones that are not based on the number of clones!

    (I should have scattered this comment with "I think/believe" disclaimers, because I cannot immediately lay my hands on any authoritative source to back me up so it is all from memory. But that would have made for tedious reading, so please take them as read. However, if anyone is interested I can try to find references.)

    Thank you, and keep up the good work, David!

    1. Thanks for your comments, and your encouragement.

      The terminology is discussed in my previous post on the close/variety topic. I entirely agree that the use of the word "clone" in viticulture is quite different from that in biology as a whole.

      The issue of mutations and variety "age" is also important, especially for Pinot noir, where there has been ample time for many mutations to occur. However, mutation rate must also vary between varieties, if no other reason than that everything else in biology is variable, so we would be surprised to find something constant. We may never know the balance between age and rate, or even whether rate is constant through time.

  3. Sorry - I haven't been reading your blog attentively enough!

    What you say is quite correct, David, but you might like to know JR et al's book Wine Grapes says: "to date there is no scientific evidence that Pinot has a higher mutation rate that any other variety". OK, so it is not conclusive, but it seems that the oft-repeated claim that Pinot mutates easily is largely based on the number of existing clones, and perhaps some anecdotal evidence from wine growers.

    On another poin, the vast majority of vinifera and vinifera-hybrid varieties are allowed in France, but there are a handful of hybrids that are actually banned. It is actually an EU regulation, but one that was very much driven by France. The instance of one banned variety was quite widely (in wine circles!) reported and discussed in June 2018, which is perhaps what prompted Bob's comment. This discussion gives the story, background, and the regs:

    1. This is an interesting topic, and I am glad that you have raised it. The banning of varieties is a political issue in the EU, which is therefore subject to change (and to being ignored by locals!). The French, in particular, have started to relax their attitude towards the topic, in response to climate change (and, possibly, to having their top wineries being bought by the Chinese!). Things are now happening now in the industry that would have been deemed impossible even 10 years ago. I suspect that many of the restrictions will be relaxed.