Molecular and hydraulic responses of grapevine to water status and phenology under long-term differential irrigation treatments

Abstract

Understanding seasonal interactions among hydraulic, chemical and molecular signalling under water deficit is crucial for improving vineyard irrigation strategies under climate change and increasing water scarcity. We aimed to test how irrigation strategies and phenology affect the hydraulic adjustment mechanisms of eight field-grown grapevine varieties under different long-term irrigation regimes: Full-irrigated (100 % ETc), deficit-irrigation (50 % Full-irrigated), and non-irrigated. Leaf pre-dawn water potential, leaf hydraulic conductivity (K_leaf), stomatal conductance, aquaporin gene expression and hormone content, were assessed at four key phenological stages, from pea-size to post-harvest. Stomatal closure was the earliest water-stress response across genotypes, while hormonal balance differentiated responsive from non-responsive genotypes regarding chemical signalling. K_leaf was primarily driven by phenology, peaking at early stages and declining thereafter. Aquaporin gene expression was both genotype- and phenology-dependent, with high activity during early stages followed by progressive down-regulation, aligned with changes in stomatal conductance and K_leaf and reflecting each variety iso-/anisohydric behaviour. This pattern confirms the role of aquaporins in grapevine hydraulic adjustments and stomatal regulation under decreasing water potentials. Aquaporins and K_leaf showed positive responses to water availability at post-harvest, indicating differential watering benefits among genotypes. Our results emphasize the need for field-phenotyping studies to fine-tune water management strategies in viticulture.