The over 300 varieties of white grapes in the world today are all the result of from two rare mutations that occured in a single red grapevine over 3,000 years ago, say Australian researchers.
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SYDNEY: A pair of ancient mutations in the genes that give grapes their red colour gave rise to the first white varieties more than 3,000 years ago, Australian scientists have found.
The discovery could give scientists the tools they need to play with grapes' colours and may perhaps lead to entirely new kinds of wine.
Researchers have long known that white wine has ancient origins - residue of white wine was found in the tomb of the Egyptian pharaoh Tutankhamun. But studies have shown that the ancestors of all modern grapes were red, and Mandy Walker, a research scientist from the CSIRO Plant Industry laboratories in Adelaide, South Australia, conducted an investigation to determine how the change occurred.
"Our research suggests that extremely rare and independent mutations in two genes produced a single white grapevine that was the parent of almost all of the world's white grape varieties," said Walker, who reports her results in The Plant Journal.
An earlier Japanese study had already shown that one of those genes regulated red colour in the skins of fruit such as apples by switching on production of a molecule called anthocyanin. The new research, conducted by Australia's national science agency, identified a second gene involved in the colour regulation pathway that had mutations in white grape varieties. Both mutations, said Walker, are required to turn grapes white.
"If only one gene had been mutated, most grapes would still be red and we would not have the more than 3,000 white grapes cultivars available today," Walker said.
The team have been able to produce a marker to predict grape colour in seedlings, which allows them to circumvent the usual two to three year wait while they grow to mature vines and produce fruit. This marker will provide an accurate indicator to select for colour traits when breeding new grapevines.
Although we won't be seeing essentially new colours, said the researchers, the discovery has potential for producing new varieties based on red and white blends. One of the areas of future study is determining if these two genes control the amount of red pigment made, possibly enabling researchers to subtly tweak the colour of red grapes.
New colour possibilities have also raised the question of whether a grape's colour has bearing on its flavour. "There hasn't been a lot of research into the scientific connection between colour and flavour," commented Paul Boss of CSIRO's Food Futures group in Sydney.
"We 'measure' flavour by using techniques to separate the mixture of compounds - there are somewhere between 500 and 600 [different ones] that are thought to contribute to flavour,"said Boss, who was not involved with Walker's study.
"Red wine flavour is dominated by oaks and additives. An example of a compound is methoxypryazine, which gives the herbaceous character to cabernets and sauvignon blancs. Another compound known as TDN, gives the kerosene-like effect to white wine," he said.
However, nobody has yet studied if these are linked to colour too.
And one question that researchers are keen to answer is whether the changes in pigmentation can affect this mixture. Walker suggested that the new findings could also assist further research into creating and grading new grape types.
