March 1, 2007 — The white grapes used to make wines like chardonnay, riesling and sauvignon blanc evolved because of a lucky genetic coincidence more than 3,000 years ago, Australian scientists have found.
Mandy Walker from CSIRO Plant Industry in Adelaide and her colleagues studied the genetics of Vitis vinifera, the grapevine species used to produce almost all the white and red wine varieties sold today.
In part, they wanted to understand how the white grape varieties of the species first evolved, Walker said. Scientists know white grapes arose as a variant of red grapes at some point in history, but not exactly how.
The new research, published in the latest issue of the Plant Journal, helps answer this question.
Specifically, Walker and her team showed that the color of grape skins is controlled by two genes, VvMYBA1 and VvMYBA2. They found that either gene can regulate the color by switching on production of a molecule called anthocyanin, which turns grape skin red. In white grapes, both the genes are mutated, meaning both ways for producing a red color are switched off.
"This was a lucky coincidence for all the white wine drinkers around the world," Walker said. "Mutations in single genes happen at a fairly low frequency, but the grapes had to have mutations in two genes to turn from red to white and that's just very, very rare."
