The readiness of grapevine rootstock to detect and respond to water stress is negatively affected by the scion. watergrape_unimi

In most of viticulture areas, Vitis vinifera is grafted onto a rootstock. The interaction between scion and rootstock shows itself as resistance to biotic and abiotic factors, such as drought. Since a lot of vineyards are located in regions where water scarcity period coincides with grape growing season, the understanding of physiological and molecular bases of rootstocks reaction towards water stress is fundamental. The effect of rootstock (101-14 and 1103 P) and grafting (own-rooted and rooted with Cabernet Sauvignon), were analyzed in two different water stress conditions. Gas exchange parameters and transcriptomic response, performed on leaf and root tissues, were evaluated. Under severe stress conditions in both genotypes, stomatal conductance, photosynthesis and evapotranspiration decreased while stem water potential increased with 1103 P showing the lower values. The grafting condition affected only photosynthesis, meaning that rootstock play a decisive role in plant water stress adaptation. The analysis of transcriptome showed that the most of differentially expressed genes were detected in roots of own-rooted and grafted 1103 P plants. The different regulation of the hormone-based signaling (ABA), ROS scavenging (flavonoids and stilbenes metabolites) and osmolyte (sugar) compound pathways revealed that 1103 P rootstock perceived readily the water scarcity and rapidly faced the stress. Molecular evidences highlighted how the scion affects negatively the stimulus perception and reactivity to drought response at the root level.