Thankfully, a grape clone is much more benign that the word suggests. It’s not the sort of fruit created by mad scientists in a lab, but instead a variation on a grape that’s been asexually reproduced from the “mother vine.”
For example, a vineyard manager might have noticed that a cluster of grapes was looser than its neighbor (a good quality for air circulation and, thus, less mildew.) In a damp climate, this might be a desirable trait and the vineyard manager wants more vines like that.
So, through cutting or grafting, this vine’s unique quality – a natural mutation – can thus be propagated.
Other characteristics that a winemaker may want to bring out in a vine might be larger or smaller fruit, disease resistance, maturation rate, or a particular color or aroma.
To get an idea of the variety offered, here is a summary of several pinot noir clones:
113 has notes of plum, cherry and cedar with a medium weight and firm tannins.
114 (the most widely planted) has notes of blueberry, mineral, cola and spice. It can be fuller-bodied than the 113 clone.
667 shows notes of dark cherry, black tea, warm earth. It is medium-bodied with soft tannins.
999 is full-bodied with medium tannins and flavors of black cherry, cassis and licorice.
Pinot noir is perhaps the most-cloned varietal. It’s prone to mutation, so variables occur with some frequency. There are likely hundreds of pinot clones; France officially recognizes over 50 of them. Cabernet sauvignon, in contrast, has about 25 recognized clones.
White grapes also get cloned. For example, California recognizes 70+ variations on chardonnay, though only 22 of sauvignon blanc.
To learn more, Bell Wine Cellars has a good description of clones that includes a comparison of three different cabernet berries. This Chicago Tribune story also breaks it down nicely; the above summary of pinot noir clones was adapted from this article. A final thanks to Lange Twins Winery & Vineyards for the photo.