Groundbreaking research in Spain’s Rioja wine region has revealed one intriguing reason why old vines can sometimes adapt better to climate change conditions.
Mutations in selected clonal variants of old vines change the vine’s physiology in helpful ways and can thus protect Rioja’s old vines.
The ICVV’s findings demonstrate the importance of protecting the genetic diversity of old bush vineyards, at a time when they are under threat from the demands of modern production.
When geneticist Pablo Carbonell-Bejerano found a spontaneous mutation in an old Tempranillo vine clone earlier this year, he discovered that the change had altered the vine’s physiology. Its red berries showed more colour intensity in the juice and skins. The effects on the vine were already known, but not the cause.
Spain’s institute for the science of vine and wine (ICVV), based in Rioja, had already reported in 2021 that higher levels of polyphenols―the compounds that play an important role in the quality of wines―can be found in grapes of this clone, known as Tempranillo negro, compared with a more widely-used Tempranillo clone. It’s a discovery that may prove helpful in protecting Rioja’s wines―and those in other places―from climate change. Together with shorter maturation cycles, higher sugar levels, and lower acidity levels, climate change in the Iberian Peninsula has also led to the loss of colour and aromas in grapes.
ICVV has screened vines aged at least 35 years old, to select natural clonal variants whose production characteristics are potentially more adaptable to growing conditions of climate change.
Pablo Carbonell-Bejerano
“Sugar levels are increasing faster than polyphenol levels when grape ripening takes place under higher temperatures, temperatures which inhibit the growth of these important compounds; therefore, wines are more alcoholic, but have lower quality levels,” said Carbonell-Bejerano.
He says that the ICVV has screened vines aged at least 35 years old, “to select natural clonal variants whose production characteristics are potentially more adaptable to growing conditions of climate change,” he told Meininger’s. Having identified variants of interest, an analysis of the vines’ DNA has allowed them to identify the mutations that could help drive quality production under climate change.
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The groundbreaking research also suggests that specific mutations present in some clonal lines selected from old vines could produce grapes with lower sugars and higher acids.
Loss of a gene leads to higher polyphenols
The Tempranillo clonal variant, originally from a vineyard in the Madrid region, was sourced from the vine nursery Viveros Vitis Navarra. Carbonell-Bejerano discovered that the old vine clone had lost a gene, and that this loss opened a way for polyphenol levels to increase in the grapes. Vines which no longer have the gene also have less of the waxes usually found on the surface of grapes.
In turn, the identification of the mutation means Carbonell-Bejerano and fellow ICVV researchers can search other clonal variants of old vines for the mutation.
Not all old vines have the same mutations. Carbonell-Bejerano explained that when the same mutation is found in a different vine, it’s not possible in most cases to tell whether the mutation occurred independently or whether the vine had simply come from a clonal propagation from another old vine with the mutation. For Carbonell-Bejerano this aspect of his research highlights the importance of protecting the genetic diversity of old vines.
ICVV researchers have, however, successfully reproduced vines from cutting of old vines, in which mutations do occur. The new vines are being reproduced and planted in rows in their experimental vineyard, where vines have been planted since the 1980s.
Ongoing research into old vine mutations
Carbonell-Bejerano and his colleagues at the ICVV have already screened around 700 vines aged 35 years and older.
“Older vines accumulate a higher number of mutations, mutations which can prompt changes in the behaviour of vines. The older the plant the more likely it is to find these mutations,” Carbonell-Bejerano said. “That said, it is more difficult to use vines that are 100 years old or more as they are less abundant.”
The ICVV’s findings show the importance of protecting the genetic diversity of old bush vineyards in the Iberian Peninsula, many of which controversially have been replaced by viticulture that uses vertical shoot positioning (VSP) trellising. While this type of viticulture increases yields and allows for machine harvesting―about 45% of Rioja’s grapes are machine harvested―it also demands more irrigation. Old bush vines, on the other hand, retain more moisture and humidity, which can be managed to reduce the impact of temperature on the vines.
The full results of his research are expected to be published in a scientific paper in early 2023. The ICVV will also expand its research to include grape varieties such as Garnacha.
