On roots, and time travel

As our club’s regularly-scheduled events are on break until next quarter, there’s time for blogging about miscellaneous somewhat-sciencey topics that cross my path. This week: roots.

One of the first things I came across when opening last week’s issue of The New Yorker was an ad—actually, two ads in a row—for a Chilean wine called Root:1. Its primary selling point: it’s made from grapes grown on ungrafted rootstock. Supposedly it will “showcase intense fruit flavors and authentic variety that prove character comes from your roots.” Given that intensity, fruit, and authenticity are probably the core of what most wine drinkers desire, it sounds like a great deal. (And for only $12 a bottle!) But to me, the even greater deal is the amazing biological phenomenon that is ungrafted wine. And the claim that this biological phenomenon-- which is scientifically pretty interesting-- is also a surefire source of a great bottle. That kind of discovery is really why I drink wine. So here’s my exploration of whether it’s as great a deal as it sounds.

 

The phylloxera louse must certainly win the prize for being the one and only insect that manages to make it into every wine-drinker’s basic education. But in case you haven’t heard yet: it devastated the French wine industry in the late 1800s, and remains a global threat. Known today as Daktulosphaira vitifoliae, it’s an extremely tiny relative of aphids that lives by gnawing on grapevine roots, and in the end it kills the vine with a million tiny holes. It originated in the Americas and American grapevines (species such as Vitis aestivalis, rupestris, riparia) evolved in tandem with it and for the most part are resistant to it, but the European wine grape (Vitis vinifera) is most certainly not. Transport of vine material from the Americas to Europe that took place in the 1800s also transported the invasive exotic insect, which, like so many invasive exotics, terrorized the local ecosystem and, in this case, also the local economy. As you might expect, a good deal of French money and effort was devoted to finding a solution—they tried everything from chemicals to flooding to hybridization—but the solution that finally won involved employing the very cause of the problem: American rootstock. Nowadays, the vast majority of European grapevines—both in Europe and in America—are grafted onto the roots of American species. The European branches produce better-tasting wine, and the American roots fight off the phylloxera.

It’s very likely you’ve heard this story before. However, you may not have heard the full story of how phylloxera was originally discovered (which wasn’t easy—for a surprisingly long time the French could not figure out what was killing their vines); the trials and tribulations of the researchers seeking the solution; the intersection of this insect with scientific greats such as Pasteur and Darwin; and the politics and egos involved. It’s a veritable saga of scientific intrigue, and I highly recommend looking up the book Wine: a scientific exploration to read the chapter written by G. Gale: Saving the vine from phylloxera: a never-ending battle. (It’s available online through Stanford libraries!)

Anyway, the phylloxera incident is to the wine industry a little like the sudden death of [insert your favorite dead celebrity here] to [insert your favorite movie or music genre here]. It changed the course of history; many people suffered greatly; but on a whole we survived, and the world that emerged has gained some romance and mystique from it. In a 2006 New York Times article, Eric Asimov wrote about the psychological effect that the problem’s solution, grafting, has had: “Still, questions nag. Does grafting somehow impede the flow of character from earth to grape? What would wines taste like if the scourge had never come?”

Asimov was writing about Bollinger Vieille Vignes Françaises, a champagne made in a very traditional way from a very small parcel of land that has somehow miraculously escaped phylloxera, so far. It’s available for about $600 per bottle. A precious few other European winemakers also tempt fate by producing small lots of wines on ungrafted vines. Wine critics who drink them often rave about the experience of going back in time, of tasting a better expression of the varietal’s true character. Ungrafted vines produce more complex, more subtly nuanced wines, better equipped to age elegantly, they say. Peter Liem, in a 2009 article for Wine & Spirits, likens ungrafted wines to unpasteurized cheeses. (Actually, I believe the more appropriate oenological counterpart to unpasteurized cheese would be a wine fermented with native yeast, but that’s an entirely different blog post, which I guarantee I will write someday. So many layers of biological “authenticity” to explore in wine!) A 2005 Decanter article by Kerin O’Keefe quotes an Italian winemaker as saying, “Winemakers have long memories...and all my life I’ve had to listen to my grandfathers and other old-timers say: ‘Ah, but Barolo before phylloxera, that was real wine’.” Liem and O’Keefe both wax poetic over Teobaldo Cappellano’s ungrafted Barolo Otin Fiorin Piè Franco, describing it as having “an inner resonance, a feeling of energy that cannot be duplicated in the other wine” (Liem, in a 2008 blog post), or “like a Fellini film: difficult to understand at first but immensely enjoyable once you do” (O’Keefe). This excitement is compounded by the sense that idealistic European growers of ungrafted vines are battling to grasp the truest pleasures of life from the jaws of impending doom: “But what if the dreaded louse should someday attack? ‘At least I’ll be able to say that I’ve had fun,’ says Cappellano with a grin.” --Also a quote from O’Keefe’s Decanter article (which, by the way, I recommend as a compelling read on this topic and one that might convince you, too, that ungrafted wines are magical).

So of course, if the winemakers at Root:1 are lucky enough to be able to produce wine from ungrafted vines, it makes perfect sense that they would try to capitalize on the allure of the authentic (which, after all, is one of the strongest possible lures to today’s wine drinkers, no?). We should add to this one other complicating piece of information (with which the Stanford readers will be familiar if they attended Chris Cheng’s wine tasting at Lyman on the 7th of this month): due to some ecological quirk, the entirety of Chile’s wine industry managed to escape phylloxera and therefore pretty much all wine grapes grown there are ungrafted. Similar pockets exist in other places around the world, including parts of Australia and New Zealand; and also places with sandy soil (because Phylloxera doesn’t survive in sand).

 

From all this, two obvious (well, to me) questions arise:

1) Is Root:1 the only winery that advertises the grafting status of its vines as a main selling point? What inspired them to brand themselves this way? Do consumers care?

2) Is there really a perceptible difference between wines made from grafted and ungrafted vines—and if there is, what’s the mechanism?

 

Question 1:

A quick Google search for “ungrafted wine” returns Root:1 twice within the top 5 results, and NO OTHER wineries until you hit the second page, at which point you find Terra Sancta, a New Zealand winery. The rest of the results are blog posts or articles on the topic, or reviews or other promotional material for Root:1. So they’re doing pretty well in terms of advertising this point.

Whether or not consumers care is a question outside the scope of this blog, but it would be exciting to explore. Given the writings I’ve encountered, I believe ungrafted wines are a niche-y but extant topic among educated wine drinkers, but I would wager that few consumers within the target population of Root:1-- the $10-12/bottle category-- seek out ungrafted wine, or necessarily even know what it means before the bottle label explains it to them. I wonder whether we should, in fact, credit Root:1 for doing a service to the wine community by educating people about Phylloxera? However, this is all speculation based purely on my own experience with the educational status of wine drinkers of this type. I’d love to learn more.

 

Question 2:

Some of the articles I cited earlier include side-by-side tastings European grafted and ungrafted wines by the same winemaker, and all claim the differences in flavor to be undeniable. But this is, of course, anecdotal evidence. We have no guarantees that the winemakers used exactly the same methods to produce the grafted and ungrafted wines; in fact, they probably didn’t. And even if we assumed they did, and we believed that the tasters didn’t allow the romance of the situation to bias their perceptions, why should rootstock make any difference? In grafted vines, the parts of the plant that produce the grapes and conduct photosynthesis are, genetically, the desired wine varietal—by what mechanism could the nature of the roots affect quality of the grapes?

Well, of course roots make a difference. Plant roots are responsible for water and nutrient uptake, and can also moderate resistance to a variety of pests and exhibit preferences for different soil types, all of which affect the physiology of the entire plant and also nature of the fruit. Different varieties of grape are certainly different at the root level in terms those characteristics. In addition, it is common knowledge that grafted grapevines, in general, often show greater growth than ungrafted grapevines. As you might expect, those who grow grapes take an interest in these things, so there have been studies aimed at identifying optimal rootstocks for various conditions and various fruiting varietals. As just one example, Jones (2009) compared the yield (grapes produced) and vigor (vegetation produced) of the same Shiraz clone grafted onto different rootstocks, and found significant heritable differences.

At the molecular level, Cookson and Ollat (2013) monitored the gene expression in Cabernet Sauvignon scions grafted to different rootstocks (hetero-grafting), and included scions re-grafted to their own rootstocks (auto-grafting) as a control to make up for the trauma a vine experiences when being cut and pasted. They found that it didn’t so much matter what rootstock the scion was grafted to, so much as it mattered whether the scion was foreign or familiar—scions grafted to foreign rootstocks respond by up-regulating a panoply of genes in a pattern similar to that associated with “hybrid vigor”—the increase in growth often observed in hybrid offspring of parents from two different varieties. In short, scions tend to grow faster and bigger and produce more fruit when grafted onto foreign roots, and it may be simply because of the other-ness of the roots.

All this may help us understand the biological mechanism behind why wines of ungrafted (aka own-rooted) vines might in theory taste different from those of grafted vines... but surprisingly few studies (at least, turned up by my brief online search) look at whether they actually do. There is one set of papers by Richard Gawel, which unfortunately Stanford doesn’t have access to. However, I’ve also come across a very recent study from eastern Washington (which seems also to be a haven for ungrafted vines). This complex project (Harbertson and Keller, 2012) compared three varietals on five rootstocks plus own-rooted, in 10 field replicates, over 3 vintages. What they found was certainly a fair amount of statistically significant variation—but almost all that variation was between scions and vintages, with rootstock causing only minor variations in the amount of anthocyanins (pigments) and tannins in the final wine. Wines from own-rooted vines did tend to be slightly higher in pH and potassium than did wines from grafted vines—the differences were statistically significant but significantly small. They also had higher tannins—which, happily, is in keeping with the anecdotal observations we’ve read. Remarkably, the researchers measured the effects of rootstock on the raw fruit as well as the effects of rootstock on the final wine, and the two groups of effects did not match. In sum, even if it turns out that rootstock has some effect on wine, it is very small, and it’s not what we would expect from the biochemistry.

So that difference in flavor that everyone raves about? Maybe there simply is magic in old roots, after all.

 

Note: this has been purely a literature review; I myself haven’t had much chance to taste ungrafted very carefully. I think I may go out and get myself some Chilean wine shortly, though. The Root:1 ad campaign has had an effect!

Also, I should disclaim that, as with most of these posts, I’m not a native to the fields of study explored here, and the papers I cite are just the ones that popped out at me upon my first search—not certifiably the best or most representative. If you know this stuff better, I’d love to hear your perspective!

 

References

Most of my sources are linked above, but in case you find an old-fashioned bibliography helpful:

Asimov, Eric. 2006. “A Champagne True to Its Roots.” The New York Times, June 14, sec. Dining & Wine. http://www.nytimes.com/2006/06/14/dining/14pour.html.

Cookson, Sarah J., and Nathalie Ollat. 2013. “Grafting with Rootstocks Induces Extensive Transcriptional Re-Programming in the Shoot Apical Meristem of Grapevine.” BMC Plant Biology 13 (1): 147.

Gale, G. 2003. “Saving the Vine from Phylloxera: A Never-Ending Battle.” In Wine: A Scientific Exploration, edited by Merton Sandler and Roger Pinder, 70–91. New York, NY: Taylor & Francis.

Harbertson, James F., and Markus Keller. 2012. “Rootstock Effects on Deficit-Irrigated Winegrapes in a Dry Climate: Grape and Wine Composition.” American Journal of Enology and Viticulture 63 (1): 40–48.

Jones, T.h., B.r. Cullis, P.r. Clingeleffer, and E.h. Rühl. 2009. “Effects of Novel Hybrid and Traditional Rootstocks on Vigour and Yield Components of Shiraz Grapevines.” Australian Journal of Grape and Wine Research 15 (3): 284–92.

Liem, Peter. 2014. “Post Pasteur.” Wine & Spirits Magazine. Accessed March 16. http://www.wineandspiritsmagazine.com/pages/f&F/1009_post_pasteur.html.

Liem, Peter. 2008. “Ungrafted Vines: It’s Not Size That Matters.” Besotted Ramblings: Peter Liem’s Blog on Champagne, Wine and Other Diversions. http://www.peterliem.com/2008/11/ungrafted-vines-its-not-size-that.html.

O’Keefe, Kerin. 2005. “The Great Escape.” Decanter Magazine, October 10. http://www.decanter.com/people-and-places/wine-articles/487476/the-great-escape.