Cabernet Labrusco - who knew?

Yesterday I received the Winter 2015 edition of the American Wine Society Wine Journal. I was delighted to find an interesting article by Peter May, titled "Cabernet Labrusco: Genesis of a New Grape Variety". It details the 20-year struggles by Jerry Rodrigues, from South Africa, in developing a new grape variety.

In 1994, Jerry was a lecturer in Biochemistry, Molecular Biology Techniques and Immunology at the University ofStellenbosch in South Africa. He took pollen from a vine to fertilize the flowers of a Cabernet Sauvignon vine. Both vines grew in his father’s garden in Plumstead, a suburb of Cape Town, where his father harvested their grapes to ferment into home-made wine.

44 seeds were obtained from a cross pollinated bunch, but the identity of only one of the parents was known. It reads like a good mystery story. AWS members can download a PDF version of the magazine from their website.

Thanks Howie

I'm off to the Cape today and I hope to be tasting Cabernet Labrusco while I'm there

Peter

I'm interested to know what you think. I wonder how cold-hardy this variety is.

Just to be clear--this variety is a cross between cabernet sauvignon and danugue noir, both of which are of species Vitis vinifera. This has nothing to do with Vitis labrusca (the grape species indigenous to North America), nor with Lambrusco (the V. vinifera variety originally from Italy).

-Paul W.

I think \Howie wondered if it inherited cold resistance along with the labrusca gene. Howie, I'll ask.

More info on that from a another article I wrote*, this is a quote from Jerry

“I noticed certain similarities in some of the microsatellite DNA markers (also known as Simple Sequence Repeats or SSRs). One of the microsatellite loci present in Cabernet labrusco, known as VVMD7, is 234 base pairs long. This short VVMD7 is also present in some Italian 'Lambrusco' accessions as well as in some American varieties, specifically those derived from Vitis labrusca (e.g. Catawba, Concord etc). It is noteworthy that both the Lambrusco cultivars and the Vitis labrusca are thought to have inherited disease-resistance genes from their wild parent counterparts. In the first case, wild genes from a species of Vitis vinifera subspecies sylvestris has introgressed into the Lambrusco genome.

In the second case, it is well-known that the wild American Vitis labrusca species harbour certain disease-resistance genes. So, hopefully, a VVMD7 of 234 bp may turn out to be an interesting disease-resistance marker. As is now well known, from the many Microsatellite SSR databases, a VVMD7 with a DNA size of about 234 base pairs occurs to an extent of less than 5%, when all of the commercial Vitis vinifera cultivars are taken into account.

So, because of this uncanny similarity in some SSRs and also because the resulting ruby-red wine looks like Lambrusco, I decided to keep a similar-sounding, and appealing, name for my new variety, namely, ‘labrusco’.

See here http://www.bellaonline.com/articles/art301369.asp
and http://www.bellaonline.com/articles/art301420.asp

I think \Howie wondered if it inherited cold resistance along with the labrusca gene. Howie, I'll ask.

Thanks. Cabernet Sauvignon and Cabernet Franc both seem to have similar cold tolerances in Upstate NY and Southern Ontario, however, Cabernet Sauvignon requires a longer growing season and often doesn't ripen properly. Both varieties took a beating over the two previous very cold winters.

I think \Howie wondered if it inherited cold resistance along with the labrusca gene. Howie, I'll ask.

Howie, cabernet labrusco has no V. labrusca genes. Both of its parents are varieties of V. vinifera. At least according to the articles I read.

-Paul W.

Their DNA can’t be to far off if they could reproduce sexually to produce hybrids (that look like grape vines).

Salute

Hi Victorwine

You are quite correct.
Vitis vinifera and, let's say, Vitis labrusca, BOTH have 39 chromosomes (diploid cells). However, Vitis rotundifolia (an American species), has 40 chromosomes. It is therefore much easier to hybridize Vitis vinifera with Vitis labrusca, but not so easy to hybridize EITHER Vitis vinifera OR Vitis labrusca with Vitis rotundifolia.
On the question of Cabernet labrusco - as Paul has mentioned, Cabernet labrusco has no V. labrusca genes - both of its parents are varieties of V. vinifera. However, we must not forget that there could be what we call, homologues of the 'same' genes in both V. vinifera AND in V. labrusca, that fulfill similar functions in both species.
However, what I have been saying in my conversations with Peter May on the subject, is that the DNA analysis on Cabernet labrusco has revealed that it has a Microsatellite DNA locus (or region), also known as a Simple Sequence Repeat (SSR) called VVMD7 with a DNA size (or length) of 234 base pairs (bp). A VVMD7 of about 234 bp has also been found in Vitis labrusca...and, interestingly, also in the Italian cultivar Lambrusco (which is a V. vinifera). So what I am suggesting is that a VVMD7 with a DNA size of about 234 bp could very well be a disease-resistance MARKER. Note that a disease-resistance marker (DNA) is NOT the actual DNA that is responsible for disease resistance, BUT it could be a DNA that has a physical position on the chromosome that could be very close to it and is likely to be co-inherited with it during a crossing or hybridization experiment.
I hope that I have somewhat clarified the confusion a little.

Ciao,

Jerry

Thank you Jerry - very good explanation.

Hi Jerry, thanks for the DNA analysis information. Is VVMD7 found in many other V. vinifera varieties, or is it fairly rare?

-Paul W.

Hi Jerry, thanks for the DNA analysis information. Is VVMD7 found in many other V. vinifera varieties, or is it fairly rare?
-Paul W.

Probably rare. The following is from Peter May's article.

Jerry analyzed his new vine’s DNA and found it had a disease-resistant gene also found in Italian Lambrusco as well as in some American Vitis labrusca varieties including Catawba and Concord.
But he was no closer to identifying the variety he had taken pollen from. Then he had a breakthrough when browsing in an antiquarian bookshop. “I found a 1960s catalogue from Pickstone’s Nurseries which was in Cape Town,” he says. “I reasoned that my father would have bought his half a dozen or so grapevine varieties, which he planted in his backyard in 1960, from such a well-known nursery. The characteristics of the old grapevine very closely matched the description of the Barbarossa grapevine in that 1960s fruit catalogue.”
But he was still not convinced. Because of similarities with Lambrusco he contacted an Agricultural Institute in Turin, Italy. He says “they agreed to collaborate with me in order to positively identify the pollen parent of my new grapevine offspring by analyzing the DNA of my new vine.
To my surprise the data fit perfectly with the French variety Danugue noir. It was really a stroke of luck, when you realize that there are still literally hundreds of Vitis vinifera cultivars whose DNA details have yet to be uploaded onto databases around the world.”
Another old book, ‘A Treatise on Viticulture,’ written in 1927 by Stellenbosch University Professor Abraham Perold, identified the table grape Barbarossa as being a synonym of Danugue. “Now I knew for sure that my father had actually bought a Barbarossa grapevine, probably from Pickstone’s Nurseries, and that it was the pollen from that grapevine that I had used in my grapevine crossing experiment.”

From the article written by Peter May (posted in Peter May’s post) it isn’t the marker (SSR) itself but the “length” or “size” (234 bp- base pairs) that’s the key.

"As is now well known, from the many Microsatellite SSR databases, a VVMD7 with a DNA size of about 234 base pairs occurs to an extent of less than 5%, when all of the commercial Vitis vinifera cultivars are taken into account."

Jerry, great investigation job! Glad to hear it is now registered.

Salute

Hi Paul

As Howie Hart has mentioned, the Simple Sequence Repeat (SSR), VVMD7 of 234 base pair (bp) in length is fairly rare
within all the commercial Vitis vinifera cultivars. It actually occurs in all these cultivars to an extent of less than 5%.
But just remember that all the members of the Genus, Vitis, will contain a set of VVMD7 alleles (two homologous DNA pieces), one set having been derived from the pollen parent and the other set from the seed parent. However, the VVMD7 lengths will be
different in most of the other cultivars (generally longer).

The shortest VVMD7 DNA is 232 bp in length and the longest VVMD7 is 262 bp in length. Each VVMD7 is the result of
adding an extra 2 bp to the smallest VVMD7, so that one would obtain a 'series' made up of 232 + 2; 232 + 4; 232 + 6
......... etc. etc. until you get 262 bp.

So, for example, take the case of my Cabernet labrusco: there are two alleles for VVMD7, which we can write down in the
following form: 234:240.

These two VVMD7 alleles came from the two parents of Cabernet labrusco (we describe the inheritance of these two
alleles as being co-dominant). So we now know that the 234 bp allele present in Cabernet labrusco was derived from
Danugue (the pollen parent) and the 240 bp allele was derived from Cabernet sauvignon (the seed parent). Get the
picture?
A bonus is that using this information (called a DNA fingerprint) from all the other SSRs, one can eventually determine who
the parents were of a particular unknown grape variety. This is how Professor Carole Meredith of UC Davis discovered
that the parents of Cabernet sauvignon were in fact, Cabernet franc and Sauvignon blanc.
Hope this clarifies a few more things.

Ciao

Jerry

[Robin Garr]

Ciao

Jerry

Jerry, all this is way over my head, but please let me add my warm welcome! It is a rare treat to have such a thorough and informed analysis. Thanks for joining the conversation, and I hope you will feel free to hang around and talk with us about wine whenever you like!

Hear Hear!!

Got it, Jerry. Thank you for the detailed explanation. So cabernet labrusco is heterozygous for the 234 bp VVMD7. I'm assuming that this is interesting because the 234 length is very common, or always present, in Vitis labrusca, and may be linked to its superior disease resistance? Has anyone tried growing cabernet labrusco ungrafted in a Phylloxera-infested area, or measured its resistance to rot, mildew, oidium, Pierce's, etc. compared to other V. vinifera cultivated varieties?

-Paul W.

Hi Paul

You do pose some interesting questions about Cabernet labrusco, some of the answers of which I am also very keen to find out. However, I will try to glean some answers for you from my experiences, both in observing the growth characteristics of Cabernet labrusco in my environment (Western Cape - Mediterranean climate) and also being somewhat familiar with some of the growth characteristics of both of its parents, namely, Cabernet sauvignon and Danugue (aka Cape Barbarossa) in this same environment.

Your question #1:
I am assuming a possible 'link' between the 234 bp VVMD7 and some sort of 'superior' disease-resistance (as you so elegantly put it). My reasoning is as follows: The pollen parent, Danugue grew in the same environment for about 44 years (in my father's back garden) after which it was uprooted by the new owners (my father's property had been sold in 2004). So I reasoned that for a grapevine such as Danugue (now positively identified through SSR analysis) to have survived so long, there was no doubt in my mind that it must have possessed some superior disease-resistance. In an old 1960's Pickstone's commercial fruit catalogue advertising Danugue (Barbarossa) - there, it was clearly stated that and I quote..."Large black round berries. Tough skin. Good carrier. Sometimes thrives in the warmer areas, and can stand summer rainfall conditions."
The clue here is that last statement (does not rot easily?). We know now that Danugue also has a VVMD7 of 234 bp in length.
Is it only coincidence?

With regard to the seed parent, Cabernet sauvignon, suffice it to say that it is still growing in that back garden even after 25 years, but it appears to be very sick and is clearly infected with grapevine leafroll virus since the Autumn leaves become totally reddish in color with the characteristic green coloration of its main veins. Its bunches of grapes are so small and not worth picking.

My original Cabernet labrusco mothervine, on the other hand, which, by the way, is now over 20 years old is totally free of any leafroll virus infection (tissue from its petioles have been tested for GLRaV-1, -2, and -3 using ELISA and PCR tests and were found to be negative for all three viruses).

Question #2:
With regard to the withstanding of Phylloxera, I am not convinced that it is immune to it, and, as you very well know, grape varieties derived from Vitis labrusca hybridization with some unknown Vitis vinifera varieties (such as Catawba, Isabella etc.) are also not really immune to Phylloxera, possibly because of the significant V. vinifera component.

I am not able to give you answers to the rest of your important questions, but, I guess that time will tell whether Cabernet labrusco has any other disease-resistance properties - I sincerely hope so.

Ciao

Jerry

Thanks, Jerry. The possible link between 234 bp VVMD7 and disease resistance does sound like a promising line of research. There's probably a PhD thesis waiting out there for some Genetics grad student.

I would hope that someone out there in viticulture land is trying to find out the genetic basis for V. vinifera's sensitivity to Phylloxera. The usual question is "why are the native American Vinifera species resistant to Phylloxera?" I think it might be more helpful to ask "why is V. vinifera so sensitive to Phylloxera?" It might be worth looking at the genetic makeup of the AxR hybrid. This has twice now been widely planted as a grafting stock in Phylloxera-infested areas, only to have it succumb later on to new mutant strains of Phylloxera.

-Palu W.

Hi Paul

Thanks for the moral support. I am inclined to agree with you that there is a possible "PhD thesis-in-waiting" for some enthusiastic genetics grad student somewhere in the world who should investigate grapevine disease resistance and their associated disease-resistance markers, one of which could very well be VVMD7. I think that some viticulture geneticists have already found a disease-resistance marker for Powdery Mildew - which is a good start!
However, to digress a little, most people ask me the most important question regarding my new cultivar... i.e. "What does my Cabernet labrusco taste like?"
Well, my 2015 Cabernet labrusco vintage did not turn out as good as my first one, i.e. the 2014 vintage. The reason was that the fermentation process of my 2015 vintage was interrupted and accidently came into contact with a little more oxygen than I intended.
So, as a consequence the wine developed a little more volatile acidity. However, the good news is that the oaking on chips for about 5 months and a further 5 months maturation in the bottle brought out a good 'vanilla' flavor - maybe even too much.
As you can well imagine, I am at the stage of experimenting with the maturation/ageing of my Cabernet labrusco - so with the next vintage (2016) I will be comparing French and American oak treatments for the ageing process.
I am uploading a photo of a glass of the 2015 Cabernet labrusco which Peter F May and I had some fun tasting yesterday. He told me that my wine had a measure of volatile acidity, which confirmed the fact that it had had too much exposure to oxygen during the fermentation process.
Oh well, we should not give up...

Ciao

Jerry

Hi Jerry,
Thanks for the up-date! I commend you on your efforts! Were the “harvest numbers” (Brix, TA, pH) in line with one another when comparing the 2014 and 2015 harvest? What is the “wine numbers” (TA and pH)? What affect does MLF and cold stabilization have on the “initial” must TA of 8.3 g/L?

Salute

Hi Victorwine

I shall try my best to answer some of your very technical questions regarding the 'harvest numbers' as you call them.
One must remember that I conducted all these measurements in my kitchen, but I tried to be as scientific as possible. I retired from teaching biochemistry two years ago.

So, I'll begin with the Cabernet labrusco 2014 harvest:
(harvested on 10 March 2014)

˚Brix: 24 (using a refractometer).
Titratable Acidity (TA): 8.7 g/L as tartaric acid.
pH: 3.3 - 3.5 (using pH paper)

Cabernet labrusco 2015 harvest:
(harvested on 23 February - - i.e two weeks earlier than the 2014 harvest due to an unusually hot summer)

˚Brix: 23 (using a hydrometer - plus an adjustment for dissolved solids).
Titratable Acidity (TA): 8.3 g/L as tartaric acid.
pH: 3.4 - 3.6 (using pH paper).

My conclusion was that the so-called "wine numbers" were very comparable for the 2014 and 2015 harvest years.
The only conclusion I could come up with in order to explain the poorer wine quality of the 2015 harvest was the fact that too much oxygen most likely spoiled the fermentation conditions, and was therefore responsible for the 'perceptibly higher' volatile acidity.
I have no means to determine (or conduct) malo-lactic fermentation (MLF) or cold stabilization, so unfortunately cannot comment on this aspect.
Hope this is a reasonable explanation...

Ciao

Jerry

This week I went to meet Jerry Rodrigues at his house in Plumstead, a suburb of Cape Town near Constantia.

cab-labrusco-peter-tastes-with-jerry.jpg

He poured me some of his Cabernet Labrusco, but as he remarks above, the sample was not in a condition to give a fair idea of what the new grape is capable of.

Jerry has an energy and determination to overcome obstacles that would have defeated most men.
He sent 60 cuttings to a professional vine nursery specializing in graftings, and they returned just one, the other’s having ‘died’. Another nursery grafted cuttings onto to incorrect an rootstock and managed to get those that survived infected with leaf-roll virus.

Jerry is himself now ridding the infected vines of the virus with advanced techniques — did I mention that he is highly technical, a specialist in micro-biology, and knows more about vine growing and plant diseases than I could comprehend. However, he admits that he is lacking winemaking skills.

cab-labrusco--jerry.jpg

In his garden he has many pots of young Cabernet Labrusco vines and his mother vine is bearing several bunches of plump ripe grapes which he intends harvesting this week when the sugar level reaches optimum and from which he expects to make a full 750ml bottle.

A viticulturist at a commercial Constantia winery has agreed to plant a row of Cabernet Labrusco so it will be interesting to see what the professionals do with Jerry’s new vine.

cab-labrusco-grapes.jpg

Peter May wrote:
“A viticulturist at a commercial Constantia winery has agreed to plant a row of Cabernet Labrusco so it will be interesting to see what the professionals do with Jerry’s new vine.”

For the “discovery” of a “new grape variety to be released for commercial use there is a certain protocol to follow. (“Discover” the actual crossing- Pre selection of seedling”-Seedling testing-Pre Testing- Lower mediate testing- Main Testing (Basically IMHO, Jerry got to this stage by dong the majority of the work all my himself). The Protocol continues for Trial Testing. If this new vine does show promise at the commercial level, I hope it would be released as a vine from “Jerry’s Private Collection”

Salute