Abstract
Given the prevailing climate change and increasing pressure on water resources for agricultural use in general and viticulture in particular, understanding the responses of grapevines to water stress is crucial to develop effective strategies to address these challenges. With this in mind, this research study including 4 experiments was conducted with the aim of exploring new agronomic tools to mitigate the detrimental effects of drought on grapevines. To this end, four experiments were conducted, both under controlled conditions and in the field. In a first study, a multi-index approach was used to gain a comprehensive understanding of grapevine responses to water stress. By integrating several physiological indicators, we aimed to assess grapevine water status and physiological processes during recurrent drought cycles. The results underline the importance of integrating different stress-related indicators. As these indicators complement each other, they allow a comprehensive understanding of grapevine responses to water stress, and thus the development of efficient deficit irrigation strategies. Furthermore, the study highlights the limitations of sap flow sensors in accurately quantifying transpiration rates, indicating their limited suitability for precise irrigation management. They, however, showed some potential for an early qualitative indication of water stress in grapevine. A manipulative field experiment was then implemented to investigate the effects of different timings and intensities of stress on two grapevine cultivars over two years. Two distinct water regimes (irrigated and rainfed) were employed in a mountain vineyard. Plant-based physiological stress indicators, yield and berry quality were evaluated. The results showed that reduced soil water availability significantly affected water status and photosynthetic activity of the vines. In addition, early water stress caused significant yield losses compared to pre-veraison stress. The study revealed that cultivars responded differently to water stress, highlighting their different drought tolerance. These differences, therefore, require the implementation of cultivar-specific irrigation management practices to ensure optimal yields and berry quality while conserving water resources. In a third experiment, the use of biostimulants was studied as a short-term adaptation strategy to alleviate water stress in grapevines. Two experiments were conducted under controlled conditions to evaluate the priming effect of different biostimulants and their dosage effect. The results of these studies showed that some biostimulants improved plant water status, photosynthetic activity and vegetative growth under water stress conditions. The study also revealed the dose-dependent effect of biostimulants, which highlights the importance of determining the optimal dosage and/or timing for the maximum efficacy of these products. Overall, the study supports the positive effects of some biostimulants and their potential to alleviate water stress in grapevines. Taken together, this work provides a thorough and comprehensive framework for understanding and managing water stress tolerance in grapevines, which is critical for sustainable viticulture. The implementation of these findings can contribute to the adaptation of grapevines to climate change.