New grape varieties give researchers a sporting chance

A chance discovery in a vineyard has given CSIRO scientists an exceptional opportunity to find out more about how new grape varieties can come about.

In the 1970s, Mac Cleggett from Langhorne Creek in South Australia propagated two oddly coloured variations of Cabernet Sauvignon he found among his vines. Single canes known as bud sports bore bronze-coloured fruit (later known as Malian) and white fruit (later known as Shalistin).

While bud sports are not a unique event - Pinot Gris is a good example - their origin is usually lost in the mists of time. In this case the occurrence of the new varieties was well-documented, giving CSIRO Plant Industry Adelaide researcher Dr Mandy Walker the opportunity to examine the genetic changes that led to their unique colouring.

The red (and black) colouring in grapes is a result of the red pigment anthocyanin being present in the berry skin. Dr Walker's research showed that the genes controlling anthocyanin synthesis were only expressed in the single outer cell layer of the grape skin in Malian berries, instead of several as in Cabernet Sauvignon. In the Shalistin variety, the anthocyanin synthesis genes had been deleted entirely, producing white grapes.

While earlier research by the team showed that most white grapes were a result of two rare simultaneous mutations in grapevine colour genes, this project demonstrated that there was a second possible mechanism for the evolution of white grapes.

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