More Questions for Andy Walker


  1. I’m very interested in the work you are doing to breed disease resistance into vinifera grapes, and understand that it takes multiple generations of breeding to breed out the off- flavor characteristics. Tell me again how many crosses you typically need to do to breed out the undesirable flavors. (I seem to recall reading that you need to get to something like 95% vinifera.) Presumably you’re continuing to cross the self-same vinifera with the vinifera hybrid. Doesn’t this lead to a greater likelihood of the expression of recessive genes, even the possibility of sterility (especially with a relatively young and slightly less stable variety like Cabernet Sauvignon)?
  2. 02_PeppersAsparagus

  3. If the female parent is the primary carrier of flavor characteristics in the cross, how much do the offspring share of those same flavor characteristics? How much variation do you typically find?
  4. When we say “desirable flavor characteristics” we might mean absence of weird, obnoxious flavors and/or the presence of certain pleasant flavors (fruitiness, proper acidity, good levels of tannin and a certain quality of tannin), but is there any way to quantify or even to better characterize that je ne sais quoi that gives certain wines (under certain conditions) a special textural element or even a certain persistence on that palate that some people call “minerality?” 03_Resveratrol(Some might call these wines “carriers or “transmitters” of terroir.) Since no one can even agree on what the term “minerality” means, is it hopeless to try to find a way to assay it? (Sorry, this is a bit of a rhetorical question.)
  5. For me, one of the definitions of a great variety is its ability to age well (and thus accrue added complexity). Typically, one might look at tannin and anthocyanin concentrations or maybe even their ratios (and perhaps acidity as well) as a predictive algorithm of a wine’s ability to age. But then there’s Pinot noir, which is low in both tannins and anthocyanins. At first blush, who would ever imagine that it would be capable of ageing? So, let me put you on the spot. Biochemically, what’s going on with Pinot that allows it to age? 04_Nebbiolo_Einstein (Non-acylated glycoside linkages?1 Higher levels of resveratrol and quercitin or something else?) If we understood that mechanism, maybe we could identify the presence of a similar process in other putatively “light” new grape varieties.
  6. As a corollary to that earlier question, if we look for the presence of “desirable” or “balanced tannins” in red wines we would most certainly end up excluding some exceptionally cool grapes in the very early selection process, to wit, Nebbiolo, (which would be a real shame). 05_Pinot_Genome Nebbiolo has luckily been retained in the viticultural repertoire presumably because of its demonstrable ability to age and develop complexity. What do you imagine the early observers of Nebbiolo saw in it? (It’s not a charmer in its youth, that’s for sure.)
  7. But this creates another more philosophical question: How might we recognize genius (as in Nebbiolo) when it is so utterly different from everything else we are looking at?
  8. Is there any evidence that “complex” grape varieties (eg. Pinot noir and Nebbiolo) have more complex genomes than more standard varieties? You’ve mentioned to me once that some varieties seem to have transposing or improvisational genes. Might this be some sort of signifier of varietal superiority or potential quality? Is this possibly the “elegance” gene or genes?
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  10. I may well be mistaken but I believe that you once told me that when you crossed solid, robust varieties – it might have been Cabernet Sauvignon or Cabernet Franc crossed with Merlot, the offspring were generally also of very high quality, sometimes even more interesting than their parents. Of course, I’m curious what you mean by the term “quality,” but what does this in fact tell us? Robust x robust will generally create robust? Certainly (delicate + complex) x (delicate + complex) does not always yield an equally gifted offspring, witness Pinotage.
  11. If you haven’t guessed, I’m haunted by the existence of Pinotage.2 I know that it was an accidental wine grape, not selected by a breeder for its superior winemaking characteristics. 07_Monks And yet, you have two just exquisite varieties giving birth to a monster.3) How can I be sure that I will not end up with a monster or many monsters?
  12. As you’ve told me on many an occasion, we don’t really know for sure whether the modern grape varieties we know were the result of an act of God/Nature or an act of man, presumably a monk with a lot of time on his hands. So, it would be impossible to know what a plant breeder of the Middle Ages was thinking when he thought about the need to improve upon Cabernet Franc by crossing it with Sauvignon Blanc, though presumably it could also have been a natural sport. I personally think of the noble Cabernet Franc variety as a far more interesting grape than Cabernet Sauvignon (and not in need of “fixing.”) What do you reckon has been the fascination with Cabernet Sauvignon; how did it ever supplant Cab Franc?
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  14. What I’m getting at: If you start with a grape that is noble, i.e., in some sense just absolutely fine the way that it is, how might one even think about wanting to make it any better? Wouldn’t it be that almost anything you do to it would somehow making it worse, specifically creating a raft of unintended consequences? I’ve heard about breeding experiments with Nebbiolo to make it “better,” i.e. darker in color or with perhaps a denser, fleshier structure, (maybe with smaller clusters that ripen more uniformly?). 09_Clos_Vougeot The results yielded a darker wine but at the same time the magical perfume and complexity was largely lost.
  15. It would seem that “great” or “noble” grape varieties may fall into two categories, those that are very adaptable to a range of climates and terroirs – like Cabernet Sauvignon and to some extent, Chardonnay, and those who produce utterly distinctive wines only in very specialized sites, i.e. Pinot noir in Burgundy. In light of this, where is one to even begin to look for nobility?
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  17. Let’s talk about Gouais blanc for a second, the ancestor of so many great vinifera grape varieties. What do you think it is about Gouais that made it such a great parent? It certainly has high acidity and that’s probably something useful. Any ideas about what else it might bring? Do we know anything about its drought tolerance?
  18. I’m thinking that one way to proceed in this project is to consider the most virile varieties – upright,4 vigorous (and presumably drought-tolerant) growers as possible male parents – Grenache, Tannat immediately come to mind. Maybe Sagrantino or Fer Servadou? Ciliegio, Troia, Aglianico?
  19. Sangiovese is thought of by some as a great grape. Myself, I don’t quite see it. What am I missing? It grows like a weed; maybe as male parent?
  20. 16. Why has there never been a Riesling cross that has ever been as interesting as Riesling itself?5
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  22. I just learned about a grape called “Rubin,” which is a Bulgarian cross of Nebbiolo x Syrah. Obviously, I want to taste it immediately and get a sense of what two genius grape varieties can do together. But even more, I would love to get into the head of the breeder who thought to do this. What do you think he was trying to accomplish?
  23. What I most want to do is learn how to get inside the head of a plant breeder. Obviously, breeding for disease resistance, or cold tolerance is a relatively straightforward proposition, but I am more interested in the idea of breeding for elegance. 12_13 I know I’m beginning to sound like a broken record here (sorry), but how do you think about elegance in wine. Where do you begin to look?
  24. I know that I must be forgetting something, indeed probably hundreds if not thousands of things. What else should I be thinking about? Thanks for your patience.
  1. Pinot noir is one of the very few vinifera grape varieties that have this unusual characteristic, and it is one reason why the wine is generally much paler in color than wine made from other varieties. It is still quite mysterious why a wine that is generally regarded as being deficient in structure will age so well. []
  2. Not only have I had atrocious Pinotage from South Africa, but the one time I worked with the grape in California, it showed precisely the same tendency to form persistent sulfurous “reductive” by-products during fermentation. []
  3. I know that South African enologists have been racking their brains (as it were), to deal with the reductive issues of Pinotage, but is it possible they have overlooked a potentially obvious solution to the Pinotage problem, to wit, grow it in much cooler areas? Maybe less heat-stressed vines will produce more nutrient-balanced musts? (I had heard that the latest research showed that by restricting fermentation temperatures to a very narrow range one could potentially cut down on creating untoward fermentation products; Pinotage, at the very least, could be thought of as a very high-maintenance variety. []
  4. Don’t know if upright growth necessarily equates with drought tolerance, but certainly will conduce to head-training, which might well be a good training strategy for creating a compact, thrifty vine. []
  5. It’s possible that Rieslaner might be almost as interesting as Riesling under certain conditions, but it’s not quite clear if it’s as adaptable as Riesling to as wide a range of wine styles. []

    9 Responses to “More Questions for Andy Walker”

    1. […] I’m very interested in the work you are doing to breed disease resistance into vinifera grapes, and understand that it takes multiple generations of breeding to breed out the off- flavor characteristics. Tell me again how many crosses you typically need to do to breed out the undesirable flavors. …read more […]

    2. john davis says:

      If grapes were grown from seed, say in a California Central Coast vineyard, would the resulting wines exhibit that foxy character attributed to indigenous American varietals? Or can a vigneron tune out foxiness so it doesn’t go all Jimi Hendrix?

      • Randall Grahm says:

        Grape seedlings should not exhibit “foxiness” unless they were bred with a vitis labrusca parent. By continuing to breed w/ vinifera, the foxiness, as it were will be bred out in a few successive generations. My guess is that it wouldn’t take much labrusca in the mix for that character to emerge. Agreed that foxiness belongs in categories other than grapes or wine.

    3. Paul says:

      Just google Walker grapes PDR1 and you can see his latest research without having to bug him directly. (PDR1 is the name of a genetic marker for resistance to Pierce’s disease.) Supposedly UC Davis was going to launch their “Pierce Resistant” vines in 2015, but I think the drought has set things back.

      As to the inbreeding question, he’s using different types of viniferas in each cross, he’s not backcrossing with the same one over and over. So it’s not wild x Cab x Cab x Cab, it’s more like wild x Cab x Chard x Zin… Although I have to say that wild x Gouais Blanc x Gouais Blanc X Gouais Blanc x Gouais Blanc x Pinot might be interesting, since the vigor would be restored in the last cross.

      According to one of his papers online, Walker is now in possession of a female-flowered 94% vinifera vine that is homozygous (carries 2 copies) for the genes for PDR1 and REN4 (a powdery mildew resistance gene). Female flower makes crosses much easier, of course, and 100% of the offspring should be resistant to PD and PM. I’m sure that it’s ultra proprietary but…. if somehow you could get permission, and you wanted to plant a seedling field blend where every vine was different.. and yet everything was PD and PM resistant… you’d want to use a vine like that as the female parent. Just plant her in the midst of an old field blend, and harvest her seeds. The hard part is getting permission. Maybe you could make an agreement with UC Davis, that any of the individual vines that turn out to be super exceptional, become their protected varieties. I’m not sure how that legality works.

    4. Randall Grahm says:

      Paul, that is extremely interesting and useful information. As you might have guessed, it’s been a little while since I’ve checked in with Andy. (I’ve been meaning to send him this post, but better really to have had a proper conversation with him.) I’m of course curious to taste what the grapes of this Omni-vinifera vine taste like. It’s very difficult sometimes to extrapolate however from how this grape shows in Davis, CA. from how it might show almost anywhere else. Alas, the female component of the cross will, I’m told (by Andy) carry most of the flavor component of the new variety, so it may or may not be so interesting flavor-wise. Agree that gouais might well have been the more interesting parent as compared to say Cabernet or Zin. Pinot, I’m afraid will likely only be growable in places like Scotland if climate change continues apace.

    5. Tasha says:

      This may show my utter lack of wine pretension (some would say naivety or perhaps even lack of sophistication), but I can’t help but wonder about crossing with Norton. Yes, I know, the dreaded foxiness, but it’s much less prevalent than in some other natives (I fully admit that I’ve had some quite enjoyable bottles of Norton!) I admit here that while enjoying my French and CA wines I’ve had a small, quiet obsession with native grapes as used elsewhere in the US and their potential to provide a truly different quality (dare I say terroir?!) to US wines — if something can just be done about the small canid with the red fur…

      Your goals are wonderful, and I’m looking forward to supporting you through what will hopefully be the development of some new and exciting grapes/wines.

      • Randall Grahm says:

        Tasha, thanks so much for your comment. While I am not a Norton-phobe by any stretch, I reckon that Norton is likely a much better candidate for the east coast than the west. One question is above and beyond breeding for “aesthetics” or “wine quality,” how ambitious might this project be as far as seeking to particular breed disease resistance into the vines. It might be a thought to introduce Pierce’s Disease resistance into the germplasm, but this would happen through a different strain of American grapes, the Vitis arizonica. Alas, this will add a number of years (maybe 6+) to the process, and unfortunately none of us is getting any younger. One might ask oneself: There are so many vinifera grape varieties; do we really need any others? We don’t necessarily need more vinifera grapes, but if you want to make a great wine in a new region and don’t have 800-1000 years to spare in iteration and observation, you may need a different methodology to develop the necessary degree of congruence of plant to the site. Another way of looking at this is to ask: How can we find true elegance in a Mediterranean climate that generally does not conduce to elegance. Rusticity, power, yes; elegance, tricky.

    6. Paul says:

      Any word from Dr. Walker?

      • Randall Grahm says:

        Had dinner with him the other night. Of course, forgot to bring along my list of questions, but had 100s of others for him. We’re making incremental progress in understanding a few things. At a minimum, I think it might well be possible to incorporate some of his work into my project and confer some good disease resistance (Pierce’s/ Powdery Mildew) on at least a few of our selections. But the meditation (and work) continues.

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