In wine and grapevines, what’s the difference between a “clone” and a “selection”?

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Dear Dr. Vinny,
In wine grapevines, what’s the difference between a “clone” and a “selection”?
—Flor, Napa, Calif.
Dear Flor,
Good question. Vine “Clones” and “selections” are related, and sometimes used interchangeably, but there is a scientific distinction between the two terms. Behind both is the idea is that grapegrowers find a vine with a specific trait they want to replicate. It could be fruit quality, resistance to fungus, desired cluster size, crop load, ripening period, or anything else a viticulturist might desire. Sometimes there’s a particular flavor, color or aroma they want to capture.
I asked former U.C. Davis professor and current Lagier Meredith vintner Carole Meredith to help me mince the words “clone” and “selection.” She explains that a “clone” is a group of grapevines that have propagated from a single known source vine, or mother plant. “Clones are usually obtained within strictly controlled national systems,” she says. The monitored process takes place in Europe, and it can take years to confirm that the new vines are indeed showing the attributes they were selected for.
“If the vines pass this test, then more buds are taken and used to propagate several more test plots, this time in several locations over several more years,” she adds. “Only if the attribute of interest is still retained and stable over several locations will the new vines be designated as a new clone, given a registration number, and distributed to commercial nurseries for propagation and sale to growers.”
Meanwhile, “selections” are common in California. “If someone finds an attribute of interest in a vineyard (let’s call it XYZ) in California, they may take budwood and use it to propagate a new vineyard,” she says, pointing out that selections aren’t necessarily taken from a single mother vine, but could be from an entire vineyard.
“The vines in the new vineyard may be referred to as the ‘XYZ’ selection,” Meredith says. “But there are never any test plots or monitoring over years to document the attribute of the new selection. The reputation of the new selection is typically just anecdotal. It may well be a genuinely distinct selection, but it is not the product of a strictly regulated clonal selection program.”
Despite the differences, clones are not necessarily considered superior to selections. But because of the process to become a clone, they may end up more consistent genetically, since they are taken from a single mother vine. Meanwhile, selections don’t go through the lengthy testing, so there’s no real assurance that a named selection is actually distinctive.
Keep in mind that, like “reserve,” the TTB doesn’t regulate these terms. I can put “Clonal Selection Reserve” on my wine label and it doesn’t have to mean anything.
—Dr. Vinny