Aussies believe all white grapes arose from a double mutation.

ABC: March 1, 2007 — The white grapes used to make wines like chardonnay, riesling and sauvignon blanc evolved because of a lucky genetic coincidence more than 3,000 years ago, Australian scientists have found.

Mandy Walker from CSIRO Plant Industry in Adelaide and her colleagues studied the genetics of Vitis vinifera, the grapevine species used to produce almost all the white and red wine varieties sold today.

In part, they wanted to understand how the white grape varieties of the species first evolved, Walker said. Scientists know white grapes arose as a variant of red grapes at some point in history, but not exactly how.

Specifically, Walker and her team showed that the color of grape skins is controlled by two genes, VvMYBA1 and VvMYBA2. They found that either gene can regulate the color by switching on production of a molecule called anthocyanin, which turns grape skin red. In white grapes, both the genes are mutated, meaning both ways for producing a red color are switched off.

"This was a lucky coincidence for all the white wine drinkers around the world," Walker said. "Mutations in single genes happen at a fairly low frequency, but the grapes had to have mutations in two genes to turn from red to white and that's just very, very rare."

When Did All This Happen?

Exactly when and where the switch might have happened isn't clear, Walker said.

"It most likely occurred before the time of Tutankhamen," she said.

White wine residue was found in flasks within the ancient Egyptian king's tomb, she explains. The researchers studied more than 55 different strains of white grape and showed that all of them contained both mutations.

"We took grapes from as many different regions of the world as possible, and the changes were all the same," she said.

This evidence suggests that all the white grape varieties have a single genetic ancestor.

"Perhaps someone walked out into a vineyard one day and saw these white grapes and wondered whether they'd make good wine," she said.

For modern winemakers, the new genetic information could prove useful as a tool for breeding new grape varieties with specific color characteristics, Walker said.

Discovery Channel.

Abstract:

White grapes arose through the mutation of two similar and adjacent regulatory genes.

Walker AR, Lee E, Bogs J, McDavid DA, Thomas MR, Robinson SP.

CSIRO Plant Industry, Adelaide Laboratory, PO Box 350, Glen Osmond, SA 5064, Australia.

Most of the thousands of grapevine cultivars (Vitis vinifera L.) can be divided into two groups, red and white, based on the presence or absence of anthocyanin in the berry skin, which has been found from genetic experiments to be controlled by a single locus. A regulatory gene, VvMYBA1, which could activate anthocyanin biosynthesis in a transient assay, was recently shown not to be transcribed in white berries due to the presence of a retrotransposon in the promoter.

We have found that the berry colour locus comprises two very similar genes, VvMYBA1 and VvMYBA2, located on a single bacterial artificial chromosome. Either gene can regulate colour in the grape berry. The white berry allele of VvMYBA2 is inactivated by two non-conservative mutations, one leads to an amino acid substitution and the other to a frame shift resulting in a smaller protein.

Transient assays showed that either mutation removed the ability of the regulator to switch on anthocyanin biosynthesis. VvMYBA2 sequence analyses, together with marker information, confirmed that 55 white cultivars all contain the white berry allele, but not red berry alleles. These results suggest that all extant white cultivars of grape vines have a common origin. We conclude that rare mutational events occurring in two adjacent genes were essential for the genesis of the white grapes used to produce the white wines and white table grapes we enjoy today.

Blackwell.

I think it was all Intelligent Design!

Because folks had long beards in those days, living as long as they did.

"We took grapes from as many different regions of the world as possible, and the changes were all the same," she said.

This evidence suggests that all the white grape varieties have a single genetic ancestor.

Patently not true. Musigny Blanc comes from a mutation of pinot noir that is less than a century old.

It's simply a case of the same mutations having occurred multiple times during history.

-Paul W.

Fascinating! I wonder if pinot noir has one mutation, since it seems to mutate so easily into pinot blanc.

Walt

No, it probably has both genes, but the variety is very prone to mutations of all sorts. Probably some of the protective genes that prevent or repair DNA transcription errors are faulty in pinot noir, leading to the high mutation rate.

-Paul W.

Paul, I sent the following email to the lead author; let's see what she says:

I posted this quote on a wine board:

"We took grapes from as many different regions of the world as possible, and the changes were all the same," she said.

This evidence suggests that all the white grape varieties have a single genetic ancestor.


Another poster wrote:

Patently not true. Musigny Blanc comes from a mutation of pinot noir that is less than a century old. It's simply a case of the same mutations having occurred multiple times during history.

Comment please.

Regards,

Robert C. Ross

[James Roscoe]

I think it was all Intelligent Design!

If it's not proof of intelligent design, what is? God knew you would need white wine Hoke.

Fascinating

But would not this 'single' incident happening also be evidence of viticulture, in that the mutated white grape vines were chosen and cloned by farmers.

Because wouldn't they otherwise naturally die out, since my understanding is that red grapes remain green until they are ready for the growing and turn red to attract birds etc that will eat them and spread the seeds.

Paul, here is Mandy Walker's reply to my email quoting your point; I've invited her to join in the discussion here:

Dear Robert

Thanks for the opportunity to comment. The person who posted the reply has a raised a very interesting point which I would like to clarify.

I am not aware of the cultivar Musigny Blanc. It is not listed in the Vitis varieties catalogue http://www.genres.de/idb/vitis/ which lists over 14000 cultivars including synonyms. However I did find this information on the link below.

An interesting mutant of old vine Pinot Noir that started producing white-skinned grapes was reportedly propagated (1936) in his "Les Perrieres" plot (cru) by Henri Gouges of Burgundy. By 1947 rooted cuttings from these vines were fairly widespread in the district. In his magisterial book "Cote D'Or", 1997, pps. 144/457, Clive Coates whimsically allots the alias name Pinot Gouges to these vines. Other sources refer to it as the Pinot Musigny. At last report there was about 2.5 ha planted, producing a white wine described by Coates as neither Meursault or Corton, but intriguing and produced in different styles that peak in about four to eight years. From http://www.wineloverspage.com/wineguest/wgg.html#pnoir

The above suggests that the cultivar in question arose as a bud sport and I will try to summarise our research in this area.

Bud sports of Pinot noir such as Pinot Gris and Pinot Blanc have been around for some time and may have arisen many times. These vines have less anthocyanin or colour in the grape skin than Pinot Noir. However they are essentially Pinot Noir vines that have undergone a genetic change which appeared as a cane with different coloured berries from the rest of the plant. The mutant cane was propagated by cutting.

Most other cultivars originated from seedlings having undergone a sexual cycle and so have a greater range of differences between them, such as berry size and shape, leaf shape, vine vigor etc. Most grape vines have two sets of similar chromosomes one inherited from each parent. Each chromosome has a similar set of genes usually in the same order as the other. In the case of white cultivars such as Chardonnay which is a descendent of Pinot and Gouais Blanc, we found that they carry a chromosome from each parent that contains the same mutations inactivating the 2 MYBA genes, which in red grapes are the controllers of skin colour. This suggests that the Pinot parent had to be carrying one chromosome with the defective MYBA genes and when we looked at the genes present in Pinot Noir, that is exactly what we found. Pinot Noir is said to be heterozygous for colour.

To elucidate how the bud sports with different coloured grapes have come about, we studied a documented case where a cane with bronze fruit was found on a Cabernet Sauvignon vine, also heterozygous for colour. When the bronze cane was propagated and grown over several hectares, a white cane was found and also propagated and named Shalistin. http://www.cleggettwines.com.au/

When we analysed the MYBA genes in these plants, we found that the part of the chromosome that carried the two active red colour genes in Cabernet was absent in Shalistin. The other chromosome in Shalistin carrying the MYBA genes has the same mutations as the mutant (white) version in Cabernet, Chardonnay, Pinot Noir, Riesling etc inherited from the ancient ancestor of white vines, published in Plant Molecular Biology http://www.springerlink.com/content/8j1 ... 2369&pi=11 .

If Cabernet or Pinot Noir were not heterozygous for berry colour, then a deletion of part of one chromosome carrying the colour genes would not be identified as the fruit would still be coloured. Some progeny of selfing this imaginary vine might have white fruit provided that there are no other important genes that have been deleted, since in these plants there would be no copies of the deleted genes instead of the usual two copies. However we have not identified cultivars of this type.

For the press release the story of the white grapes and how they arose was simplified. However it is still true that the ancient ancestor of white vines is also an ancestor of Pinot Noir and Cabernet Sauvignon and their bud sports as evidenced by the inheritance of the same mutations the MYBA genes in the white variant of the chromosome carried by these plants.

Mandy Walker

CSIRO Plant Industry

Adelaide

Fascinating

But would not this 'single' incident happening also be evidence of viticulture, in that the mutated white grape vines were chosen and cloned by farmers.

Because wouldn't they otherwise naturally die out, since my understanding is that red grapes remain green until they are ready for the growing and turn red to attract birds etc that will eat them and spread the seeds.

Probably, but that might make the event older by maybe 2,000 years.

Thanks, Bob. Mandy's reply clarifies things.

I was indeed referring to the Gouges vines, and Mandy is correct that they are clones isolated from a bud sport and not bred via sexual reproduction.

It wasn't clear from the original posting in this thread that only the varieties isolated from seeds were being considered in the remark about all white grape varieties being descended from a mutant single ancestor.

Nearly all, if not all, vine varieties are propagated these days by cloning of branches and buds, not from seedlings, precisely to prevent genetic recombination (i.e., most vine varieties don't "breed true"). Only nurseries intent on producing new varieties bother with growing seedlings. I therefore think that new varieties that occur from mutations in the bud tissue (bud sports) are, once isolated and propagated, just as valid new varieties as those obtained from sexual reproduction of the vine (seedlings).

-Paul W.

Paul W wrote: I therefore think that new varieties that occur from mutations in the bud tissue (bud sports) are, once isolated and propagated, just as valid new varieties as those obtained from sexual reproduction of the vine (seedlings).
.
That’s exactly how I thought If a clone (clone of a variety, or clone of a clone) has become so relevant to man that he/she gives it its “own name” the clone now becomes a “new valid variety”. But from a genetics point of view this is not the case. From a visual aspect the vines and berries might be different, the wines produced from such grapes might be totally different but genetically the vines are identical. For a variety of a species to arise sexual reproduction has to take place, two different parents (varieties) usually of the same species.

The following was taken from an old WLDG discussion;

The Difference between a “Variety” and a “Clone”
Dr. Carole Meredith on Wine Lovers Page Forum

Zinfandel and Primitivo and Crljenak kastelanski are 3 names used for 1 variety. All three are the same variety, just like the synonyms Syrah/Shiraz or Tempranillo/Valdepenas. Although the variety has been in Croatia much longer than in Italy or the United States, Zinfandel is not “descended” from Crljenak in the genetic sense. Zin and Primitivo and Crljenak are all derived by vegetative multiplication (i.e., cuttings and buds) from a single original seedling.
Yes, there are clearly some differences between the vines called Zinfandel that we have been growing in California for 100+ years and those grown in Italy and called Primitivo. But those differences are clonal differences, not varietal differences. They are the same kinds of differences that can be observed between some clones of Syrah or between some clones of Chardonnay.

Here’s my boilerplate explanation of the distinction between clones and varieties:

DNA studies have clarified the distinction between a variety and clone. All vines of all clones of a variety are derived (by asexual propagation, i.e. cuttings and buds) from a single original vine. The single original vine arose as a seedling that was the result of a sexual union between two parent vines, almost always of two different varieties. All clonal variation, on the other hand, arises as a result of rare and random somatic mutations (i.e., not sexual) that occur in all vines. Sometimes such a mutation has a visible or otherwise detectable (e.g. aroma difference) effect and a vine carrying it will be preferentially used for propagation wood for new vineyards. But often it is just chance that one mutation survives to the next generation of vineyards and another doesn't. The mutations accumulate over time and eventually clones diverge from each other.
But clonal differences are very tiny compared to the genetic differences between varieties. The standard DNA markers used to identify grape varieties will produce the same DNA profile for all clones in the variety. It took us years before we finally found any DNA markers at all that would separate any clones of Pinot or Chardonnay, and they only differentiated a few clones. The differences between varieties have their origin in sexual genetic processes (i.e., meiosis and recombination) whereas the differences between clones arise only from asexual processes.
This discussion becomes problematic in the case of Pinot noir, Pinot blanc, Pinot gris and Meunier, however, in that they are all, in fact, clones of a single variety (i.e., they all arose from a single original seedling and all have the same DNA profile) even though wine producers and consumers consider them to be separate varieties because they are so visibly different. The French language deals with this concept better in that all 4 are considered to be the same 'cepage'.
(End of boilerplate).

DNA profiling unambiguously distinguishes between individuals that have originated from separate sexual events. In humans, this means that DNA profiling can distinguish individual people from each other if they have originated from separate sexual events, but it cannot differentiate identical (i.e., monozygotic) twins. In grapevines, this means that DNA profiling can distinguish individual varieties from each other (like Chardonnay vs. Melon or Cabernet vs. Merlot) because they originated from separate sexual events, but it cannot differentiate clones within the same variety because they originated from a single sexual event.

Carole Meredith
University of California, Davis (sometimes)


Salute

I find myself wondering what would happen if one or both of the color genes were to be switched back on in white varieties.

What would a Chardonnay Noir taste like? Would a Sauvignon Noir be more or less interesting than a Sauvignon Blanc?

I find myself wondering what would happen if one or both of the color genes were to be switched back on in white varieties.

What would a Chardonnay Noir taste like? Would a Sauvignon Noir be more or less interesting than a Sauvignon Blanc?

Well, this kinda sorta has happened. The variety we now know as cabernet sauvignon has been found to be a cross between sauvignon blanc and cabernet franc. Now, it's possible (indeed, likely) that cab. sauvignon inherited both color genes from cab. franc. But for many years the linguistically obvious cross sauvignon blanc x cabernet franc was summarily dismissed as cabernet sauvignon's parentage because it seemed absurd that crossing a dark grape with a white grape would yield an even darker grape. Yet indeed it was the case!

-Paul W.

Certainly the variation that results from sexual reproduction (seedlings, for vines) is greater than what comes about from bud mutation, which is almost invariably a point mutation in a single gene. No argument here.

But with domesticated Vitis vinifera, we are dealing with a plant whose reproduction is almost exclusively controlled by mankind. And the vast majority of that is vegetal (cloning using budwood) versus sexual. Whatever the DNA analysis statistics might say, the wine yielded by Musigny Blanc (the Gouges clone of pinot noir) is nearly as significantly different from pinot noir as is chardonnay vs. pinot noir. So what if it's only one or two genetic mutations away from ordinary pinot noir? The point is that it's one or two significant mutations away.

I do not mean to dismiss or denigrate the excellent and important analysis work that the Australian team has done. It is indeed interesting and important to know that the major white grape varieties isolated via sexual reproduction all seem to arise from mutation events involving only two genes. But a very significant number of the white grape varieties contributing to white wine throughout the world arose via bud mutation and vegetal propagation of the isolated clone, and those varieties ARE considered varieties in their own right, and whatever their ancestry they cannot be ignored.

-Paul W.

Among the Cabernet Sauvignon family of grapes aren’t there clones or mutants that possess grey and white berries?

Salute

Yes there are colour mutants among the Cabernet Sauvignon group, including Malian and Shalistin which arose here in Australia http://www.cleggettwines.com.au/ We studied the changes in the colour genes and found a large DNA deletion in Shalistin of the two colour genes that make Cabernet red. We published this work in Plant Molecular Biology (2006) 62 623-635 entitled Two new grape cultivars, bud sports of Cabernet Sauvignon bearing pale-coloured berries, are the result of deletion of two regulatory genes of the berry colour locus by Amanda R. Walker, Elizabeth Lee and Simon P. Robinson.

On the point made by Paul that Cab Sav has more colour than either of its parents. This observation demonstrates how complex organisms are. There are many genes in a grape vine and many of them can influence or modify the effects of other genes.

I find myself wondering what would happen if one or both of the color genes were to be switched back on in white varieties.

What would a Chardonnay Noir taste like? Would a Sauvignon Noir be more or less interesting than a Sauvignon Blanc?

It would depend on how you vinify the grape. If you vinify your Sauvignon Noir as you would Sauvignon Blanc I'd think it would taste pretty much the same. If it was done to make a red wine, who knows..

Some time ago, I spent some time trying to establish why the different colour grapes were (usually) vinified differently. I got no clear answers, but as far as I could work out... purple grapes are fermented on the skins because the tannins and colour are valued... green grapes are pressed before fermentation because their skins are too tannic and there is nothing to be gained colour-wise.

But I am not pretending this is the final word on the subject - I'd appreciate further comments.

This must fall in the category "Very Naive Questions", but...

Do these conclusions apply to all wine grapes or just the species vitis vinifera?

Many Labrusca grapes that are used to make "white" wines are themselves darkly pigmented. Delaware is an example.

Many Labrusca grapes that are used to make "white" wines are themselves darkly pigmented. Delaware is an example.

There are of course vinifera examples too. The most common is probably the use of PN in Champagne. I don't think green grapes are ever fermented on the skins, though there is sometimes limited skin maceration.

The discussion here applies not only to different species of grapes, but to almost all plant life. When you take pollen and put it on a pistil you get seeds, each of which becomes a new variety. When a plant changes itself by itself it is either called a clone or sport. That plant and its cuttings will remain true to its new identity for generations or longer.

We know the two genes responsible for the pigmentation. It would seem a pretty trivial thing to GM some Zin DNA and...voila...a White Zinfandel vine!! SutterHome would love it.
Tom

Well, this kinda sorta has happened. The variety we now know as cabernet sauvignon has been found to be a cross between sauvignon blanc and cabernet franc. Now, it's possible (indeed, likely) that cab. sauvignon inherited both color genes from cab. franc. But for many years the linguistically obvious cross sauvignon blanc x cabernet franc was summarily dismissed as cabernet sauvignon's parentage because it seemed absurd that crossing a dark grape with a white grape would yield an even darker grape. Yet indeed it was the case!

-Paul W.

Yeah, kinda sorta, but it is a cross, and necessarily brings characteristics other than color from the red parent. To my mind, this is not close enough to serve as an example.