Root water uptake patterns in rootstock-scion interactions influence grape water use strategies in a Mediterranean vineyard

Abstract

Increasing drought is the most important impact of the ongoing climate change in the Mediterranean Basin, and it is predicted to result in productivity decreases and changes in grape quality. Therefore, viticulture in the Mediterranean wine growing regions has the pressing need to adjust to climate change by using more resilient varieties and rootstocks. Rootstocks contribute to the regulation of scion water use and determine resource availability through the development of the root system. However, there is a lack of knowledge on the spatio-temporal patterns in root water uptake, and how rootstocks determine them by interacting with the environment, which prevents efficient knowledge transfer into practice. Indeed, belowground water relations are key for grapevine physiology and thus productivity, but they remain largely undisclosed. To address this knowledge gap, the present work aims at assessing the effects of three well-established rootstocks – 41B Millardet et de Grasset (41B), 140 Ruggeri (140Ru), and 110 Richter (110-R) – on the depth of water uptake and the vine performance of the cultivars Grenache, Cabernet Sauvignon and Marselan (3 varieties x 3 rootstocks in 3 blocks) at an experimental vineyard located in the NE Iberian Peninsula. To evaluate the effects of the scion/rootstock interaction, physiological phenotyping was carried out using techniques such as leaf gas exchange measurements, pressure-chamber-based water potential and airborne sensing using thermal and multispectral cameras. We also employed isotopic techniques (δ2H and δ18O) to infer the depth of root water uptake. In particular, we aimed to estimate the relative contribution of various water sources (soil at different depths) to water uptake, across three different rootstocks. The results indicate that although small physiological differences at the leaf level exist among rootstock-scion combinations, a significant effect of the rootstock is observed in terms of water status, more particularly, in the predawn water potential, which could be related to contrasting root exploration capacities. This highlights the ability of certain rootstocks to explore deeper soil layers. In this work we will discuss the physiological relations in scion/rootstock interaction under the scope of climate change scenarios and the usefulness of isotopic tracers as powerful tools to infer the temporal and spatial origin of water taken up by grapevine roots.