Increased temperature, elevated atmospheric CO₂ and water deficit modify grape composition of different ‘Tempranillo’ (Vitis vinifera L.) clones

Grape composition is strongly influenced by climate growing conditions and their modifications, as expected in the coming years (increased temperature, elevated atmospheric CO₂ levels and water scarcity), may significantly modify the biochemical composition of berries at harvest, and thus wine typicity. The rich intra-varietal diversity opens the possibility to select better adapted plant material in order to mitigate the potential negative effects of climate change on grape quality. The effects of increased temperature, elevated atmospheric CO₂ levels and water deficit on grape composition of ‘Tempranillo’ clones with different length of their reproductive cycle were studied with the aim of detecting potential interesting traits among them. Fruit-bearing cuttings were grown in temperature gradient greenhouses and in growth chamber greenhouses under two temperatures (ambient temperature versus ambient temperature +4°C), two CO₂ levels (400 versus 700 ppm) and two water regimes (well-watered versus water deficit), both in combination or independently, in order to simulate future climate change scenarios. The concentration of sugars, organic acids and anthocyanins in grapes was measured. Elevated temperature hastened sugar accumulation in grapes, both acting individually and in combination with high CO₂. However, this effect was mitigated by water deficit. On the other hand, elevated temperature increased malic acid degradation, notably when combined with elevated CO₂ level and water deficit. Total anthocyanin levels at maturity were not strongly modified by the increase of temperature and CO₂ levels but the combination of elevated temperature, high CO₂ and water deficit led to a strong decrease of anthocyanin levels. The magnitude of these alterations was different among clones indicating intra-varietal variability in the response of ‘Tempranillo’ to climate conditions. These results highlight the importance of multi-stress approaches to provide realistic insights into the response of clones to optimize the adaptation of traditional cultivars in their growing regions.