Water use efficiency of Chardonnay under different grafting combinations in the viticultural area of Franciacorta

Abstract

Drought poses a challenge to future viticulture, exacerbated by climate change, which increases the frequency and severity of water shortages. The use of tolerant rootstocks is considered a sustainable strategy for facing drought, increasing water use efficiency (WUE) and maintaining the production and the quality of grapes and wines. In fact, under water-limited conditions rootstock induces stomatal closure, a critical strategy to minimize water loss, although it can also reduce photosynthesis and consequently vegetative growth or grape ripening. New promising rootstocks have been recently selected for facing abiotic stresses, i.e. M1, M2, M3 and M4, and their stress tolerance is currently under investigation, considering interactions with scion, climate and soil properties. The aim of this study is to investigate the effect of the new M-rootstocks on the water stress response of Chardonnay in the viticultural area of Franciacorta, and to explore their potential for sparkling wine production under changing climate scenarios. The experiment was conducted in 2023 and 2024 in a 10 years old pilot vineyard, characterized by loamy clay soils. Chardonnay vines were compared in 6 grafting combinations, including the four M rootstocks, SO4 and 1103 Paulsen. During the two analyzed vegetative seasons, physiological activity of vines was monitored, in terms of water potential, osmotic potential, gas exchange, WUE, and chlorophyll fluorescence. At harvest, productive and qualitative parameters of grapes were detected.

Under absent or mild water stress, M-rootstocks induced higher WUE to Chardonnay than traditional rootstock. Under moderate to severe stress, WUE was maximized by the grafting combinations with rootstocks M2 and 1103 Paulsen at midday. Different daily dynamics were observed for M4 and SO4, which induced stomatal closure at midday and high gas exchange and WUE in the morning. At harvest, a significant effect of the grafting combination was observed on grape acidity, which was higher for rootstocks M4 and SO4.

These results suggest that the use of new rootstocks in Franciacorta allows to reduce water use and to enhance the quality of grapes for sparkling wine production. Further studies on adaptive strategies of drought-tolerant rootstocks will provide better insights into their performance under different environmental conditions and grafting combinations.