As part of a recent study, geneticist Sean Myles and a team of viticulturists from multiple institutions around the world examined and compared the DNA of more than 1,000 vitis vinifera and syvlestris wine and table grapes in the U.S. Department of Agriculture’s seed bank, where plantings from all USDA-sanctioned grape varieties are stored. What they found surprised them—about half the grapes belong to one giant family. Pinot Noir begat Chardonnay, or vice versa. Cabernet Sauvignon is either a grandchild or sibling to Merlot. Syrah and Viognier are brother and sister. And the patriarch of most of the wine grapes grown in America appears to be Traminer, which probably counts Grüner Veltliner, Verdelho, Sauvignon Blanc and Chenin Blanc among its immediate offspring.
As in old royal families, it appears domesticated grapes have kept their good names by avoiding much breeding outside the family. And as in old royal families, this could spell poor health for our princeliest varieties. A new disease preying on vinifera could cause significant damage, even disaster.
“The high degree of relatedness among all the individuals was pretty surprising,” said Myles. “We haven’t seen that in any other domesticated species to date.” Considering that each cultivar, such as Chardonnay or Cabernet Franc, is the equivalent of one specimen, this, in human terms, would mean a United States census tallying only 1,000 people, half of them closely related and only a dozen or so particularly famous.
The reason two sibling cultivars can make wildly different styles of wine is the high degree of genetic diversity in each variety. “Looking at the difference between two grape cultivars on a DNA level is about the same as looking at the difference between a human and a chimpanzee,” said Myles, a postdoctoral geneticist at Stanford, who originally began mapping the grape genome to try and understand the DNA patterns in an organism of such high genetic diversity. The study was published in the Proceedings of the National Academy of Sciences journal in December.
But as unique as each grape variety is, humans have been relying on many of the same wine grapes for hundreds, even thousands, of years. Vegetative propagation, a way of planting and reproducing our beloved varieties asexually by simply taking cuttings from the best vines, makes it easy for growers to fine-tune their cultivation of specific varieties. As John Martini, owner of Anthony Road Wines in the Finger Lakes puts it, “You take a stick and stick it in the ground.”
But there’s a downside. “Pathogens keep evolving, but the cultivars haven’t,” said Myles. “Cultivars have been sitting ducks for pathogens.” According to Myles, as much as 70 percent of all fungicides used in the United States are applied to grapevines. “We spray a lot [more than in the past] now, and if we keep using the same cultivars, we’ll spray a lot more into the future.” Chemical companies can outfox diseases, but there’s a potential environmental cost—or new regulations will restrict the use of the sprays. Meanwhile, “the plants themselves are genetically standing still, and many of them have been for hundreds of years,” said Myles.
What Myles and his team have done, using a technology called a genotypic microarray, or gene chip, is map the genomes of individual grapes. Gene mapping is no longer science fiction; increasingly, it is cheap and easy. In 2004, it cost $300 million to sequence a human genome. Today, it runs about $10,000.
Traditional grape breeding is a notoriously fickle, slow and costly endeavor. But this new technology can allow geneticists to identify, at the DNA level and the seedling stage of development, what genetic codes will trigger qualities like smaller berries or cold resistance. If Pinot Noir is bred with Merlot, then breeders can look at 100 offspring in their infancy, pick out which ones will have, say, the best color, lowest yields and highest disease tolerance and proceed to plant only those successful crosses—instead of a vineyard of mostly duds. The possibilities are entertaining: “A big, fruit-forward Zin that has a hint of Muscat aroma,” imagined Myles. “All of these DNA variants that contribute to things we call quality in a grape—they haven’t been piled into a single cultivar at all.”
But would anyone drink it? Consumers are looking for different qualities in wine grapes than they look for in other crops like corn, which has been bred for disease resistance and high yields. This quality is not necessarily desirable in wine grapes, though, and no corn cultivar has the same type of consumer reputation to uphold as, say, Chardonnay.
“People grow Tempranillo in Nova Scotia,” said Myles of his home province, where he and his wife make white wine from the L'Acadie Blanc hybrid. “Because if you put Tempranillo on the bottle, people will buy it.” Myles blames variety favoritism—or “grape racism,” as he calls it—for resistance among drinkers to the types of crosses that programs like his aim for, especially when the result is not entirely vinifera.
Hybrid grapes, varieties in which at least one progenitor is from a non-vinifera grape species, are often hardy in cold weather and resistant to pests, but many of the wines share the “grapey” or “foxy” flavors of non-vinifera wines, and the reputation of the category has suffered for this. “Drink a bunch of hybrids and 99 percent are totally suboptimal. But you’ve got to support these programs in order to turn that around,” said Myles.
Martini agrees that with skill, such undesirable flavors can be avoided. “[Foxiness] I think relates to as much cellar stuff as out in the vineyards,” he said. And some hybrids are up to 98 percent vinifera.
Martini, who uses the hybrids Cayuga White and Rougeon in blends and bottles a varietal Vignoles, thinks that lack of recognition is the greater problem facing his hybrids in the marketplace. “In even the worst winters, Vignoles has withstood many [frosts] when we’ve lost a lot of buds in other varieties,” said Martini, who also grows Riesling and other vinifera varieties.
But lack of consumer familiarity is “why the only one that we put out with a varietal label is Vignoles,” said Martini. “The Vignoles is a good standalone varietal. It makes a very nice, interesting wine. It’s got some really unique characteristics in the flavor profile, but it’s a hand sell. I run into consumers and they go, ‘Oh, is that Viognier?’”
Despite the marketing challenge, grape breeding represents an attractive way to create pathogen resistance without relying on genetically modified grapes. While organic farming can eliminate the need for chemicals, it is often impossible in humid regions. Newly-bred grape cultivars, with their built-in defenses, would adapt much more robustly to organic farming methods.
Myles hopes that consumers will broaden their palates and curtail their prejudices against new and unfamiliar varieties before a potential catastrophe. The banana industry, which relies primarily on just one cultivar, has been suffering from an incurable root disease. Nineteenth-century vintners who lost all their vines to phylloxera actually “got lucky, because it wasn’t affecting the scion, it was only affecting the rootstock,” so traditional grapes never had to be genetically shuffled, said Myles. Vinifera grapes were saved by grafting the vines onto American rootstocks. But with pathogens ever evolving, it could be just a matter of time before the most valued parts of the vine come under heavy attack without adequate defenses.