Researchers at the University of California, Davis, have released five new wine grape varietals – the first in nearly four decades, according to a university press release.
The five varietals were bred to be highly resistant to Pierce’s disease, a bacterial disease that is fatal for grapevines. Without current efforts to contain the population of “sharpshooters,” the insect that spreads Pierce’s disease to grape vines, there would be “very little viticulture in California,” according to Andy Walker, the geneticist and professor of viticulture and enology at Davis who is responsible for the creation of the new varietals.
Walker, who began his work breeding the varietals more than two decades ago in the late 1990s, said the new wine grapes could be especially useful in the southern United States, where Pierce’s disease is especially rampant, and in affected portions of California wine country. Pierce’s disease often appears in riparian, or riverside, habitats, Walker said.
“These hot spots where Pierce’s disease is intense—you could recuperate that land, and use it to grow grapes again,” Walker added.
He said the new breeds – three reds and two whites – will be used primarily as blending wines, not necessarily as single varietals. Growers sometimes shy away from new names, Walker said, noting that acceptance for the newcomers could grow as the grapes become more widespread.
“Certainly in the South, they won’t worry about the name,” he said. “I think climate change will change the way we grow grapes dramatically – we’re not going to change the locations we grow grapes, because we’ve invested (in those areas). We’ll have to grow grapes that are better suited (to warmer temperatures).”
Researchers have found that Pierce’s disease is essentially curbed by cold weather; it forms what Walker calls “a weird smile” through the continental United States. It is present on the West Coast as far north as southern Mendocino County, Walker said. From there, its presence dots the American South and surges slightly north, hitting the East Coast as far as Virginia.
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Because Pierce’s disease is kept in check by cold weather, according to Walker, rising temperatures could mean its eventual spread farther north – and emphasize the importance of the new varietals.
Adam Tolmach, owner and winemaker of The Ojai Vineyard in Ojai, in Southern California, planted four of the five new breeds on a 1.2 acre plot of land – the same plot where Pierce’s disease had killed his vines almost 15 years prior.
“I wasn’t interested in planting in that plot again until I heard about these new Pierce’s disease resistant grape varietals,” Tolmach said in the university’s press release. This was the first harvest for the grapes, he said. “We’ve just begun to evaluate the wine, but I’m very encouraged.”
Walker bred the varieties in both Davis and in Napa using Vitis vinifera, the chief grape breed used in modern day winemaking, and the wild species Vitis arizonica, the Pierce’s disease-resistant varietal. It was “a fluke” that researchers even discovered arizonica’s resistant properties, Walker added, noting it was the result of work done by his predecessor, the last Davis researcher to release new grape varietals in the 1980s.
It took two decades and many generations of grape breeding to cultivate the five varietals as they exist today, Walker said. He emphasized the support of his colleagues and strong, consistent support from the Pierce’s disease board, which has been heavily invested in the mitigation of the disease.
Ultimately, this generation of the grapes – the one being released – is 97 percent resistant to Pierce’s disease. During the final stages of grape breeding, researchers crossed the Pierce’s disease-resistant wine grapes with “high quality wine grapes,” creating a high percentage of both quality and resistance.
“The neat thing about this process is that in that last generation, when you make that last cross with high quality wine grapes – the (grapes) will take on the characteristics of those grapes,” Walker said. “So they will look a bit like Chardonnay or Cabernet grapes. They take on not only the appearance, but the qualities as well.”