How did DNA reveal the parents of Cabernet Sauvignon?

A DNA test showed that Cabernet Sauvignon is the child of two other grapes, Cabernet franc and Sauvignon blanc. In 1996 a team led by Carole Meredith at UC Davis used DNA typing to find that out, and the likeliest story is a chance crossing in the 17th century, in France. Before that, the grape was rumoured to have ancient origins, perhaps being the Biturica grape of Roman wine mentioned by Pliny the Elder.

Nobody was entirely surprised, because the clues had been in plain sight. The parentage had been suspected from the similar names and from shared aromas: the blackcurrant and pencil box notes of Cabernet franc, and the grassiness of Sauvignon blanc. DNA turned a suspicion into evidence.

It also settled where the grape began. Since both parents are Bordeaux varieties, grapevine historians believe Cabernet Sauvignon originated in Bordeaux. Its popularity is often attributed to easy cultivation: thick skins and hardy, low-yielding vines that bud late to avoid frost.

This was a family tree for a plant with thousands of relatives. Vitis vinifera has between 5,000 and 10,000 varieties, though only a few matter commercially. UC Davis DNA fingerprinting also suggests that Chardonnay is a cross between Pinot noir and Gouais blanc, a peasants' grape, whose name comes from an old French word of derision. So fine wines have humble relatives.