Back to the future: 2019’s extreme heatwave didn’t kill all grape varieties

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Back to the future: the extreme heat wave of 2019 did not kill all grape varieti
Back to the future: the extreme heat wave of 2019 did not kill all grape varieties © Gérard PAILLARD - INRAE

As heatwaves intensify in France, we need to adapt our crops. A new study by INRAE and Institut Agro reveals the genome regions involved in tolerance to extreme temperatures in grapevines - thanks to an experiment using the exceptional canicular episode of June 2019. Results published on February 7 in New Phytologist.

46.0°C in the shade. This was the highest temperature ever recorded in France on June 28, 2019 in Vérargues, Hérault, due to the passage of a mass of scorching air from the Sahara. A few kilometers away on that day, scientists from the Institut Agro and INRAE were conducting an experiment involving over 250 pot-grown grape varieties at the Pierre-Galet experimental vineyard in Montpellier. These conditions enabled a "life-size" assessment to be made of how the diversity of grape varieties responds to extreme temperatures.

Indeed, a few hours after the temperature peak, some of the vines’ foliage was literally scorched. But then what was the surface temperature of the brightest leaves - almost 54°C, according to the researchers’ simulations. A value beyond the viable thermal limit for many plants.

But not all grape varieties suffered the same fate: some showed very severe damage, while others emerged unscathed from the heat wave. In view of this, the scientists developed an "association genetics" approach: by cross-referencing symptom measurements with available information on the diversity of grape varieties and their genotypes, they identified the parts of the genome involved in the measured responses.

Six regions of the genome have been identified as being involved in responses to heat stress. Within these regions, researchers have identified groups of genes, but do not yet know whether only one of them is important, or whether they act in concert. These genes are correlated with oxidative stress management (linked to the production of molecules that destabilize plant cells) and signaling activated at high temperatures, but surprisingly not transpiration. Although transpiration may have lowered surface temperature by almost 5°C.

This result could be explained by the trade-off between the need for water to cool the plant and the availability of water in the soil. Indeed, heatwaves are often coupled with dry spells, and maintaining water in the soil and within the plant is just as crucial as regulating the plant’s temperature to ensure its integrity.

The intensity and frequency of extreme events will increase in the future climate, and the June 2019 episode enabled researchers to explore some of the genetic potential of grapevines in such conditions. These results offer the prospect of major progress in varietal improvement in viticulture, and perhaps in other cultivated species. A solution to be combined with other agronomic levers to adapt our crops to climate change.


Coupel-Ledru A., Westgeest A.J., Albasha R. et al. (2024) Clusters of grapevine genes for a burning world. New Phytologist . DOI: 10.1111/nph.19540 2024_Pantin_Retour vers le futur la canicule extrême de 2019 na n’eu raison de tous les cépages_VF.pdf pdf - 680.63 KB