Pinot pigment mutations tell scientists a colourful story

Illustration / Rod Emmerson

That cool pinot gris you enjoy after a tough day at the office is really just a mutant spin-out of pinot noir - or so scientists have found.

Researchers have pin-pointed the genetic process that determines whether pinot grapes become red or white.

Pinot noir, predominantly grown in the cooler regions, makes up about 9 per cent of wine production in New Zealand, while pinot gris, our third most popular white variety, accounts for around 6 per cent.

A new study, led by researchers at INRA Colmar in France and published in the journal PLOS Genetics, found the colour of grapes within the pinot family spawn from naturally occurring mutations which selectively shut down the genes responsible for the synthesis of red pigments, called anthocyanins.

Viticulturalists have long known how spontaneous events in the genomes of some vines can lead to differences between individual plants, but the molecular mechanisms at play have now been seen in unprecedented detail.

The team studied 33 clones of pinot noir, pinot gris and pinot blanc and observed how large-scale exchanges between homologous chromosomes, sometimes associated with deletions, selectively shut down the genes that induce the biosynthesis of anthocyanins.

These mutations, which occur in a cell, propagated to form a distinct cell layer, resulting in genetically diverse, chimeric plants that could later enable pinot gris to arise from pinot noir.

In this process, a pinot noir skin surrounded internal cells that had mutated to pinot blanc.

Subsequently, pinot blanc could emerge from pinot gris as a result of cellular rearrangements that spread the mutations throughout the plant.

Dr Chris Winefield, a senior lecturer in plant biochemistry at Lincoln University, doubted the findings would have any direct implications for New Zealand's wine industry.

Some odd mutations seen here included gewurztraminer plants that were producing albino grapes each year, and riesling plants producing unusually large berries.