Long-Term Irrigation History Provides Evidence for Drought Memory in Clonally Propagated Grapevines During Water Deficit and Recovery.

Grapevine adapts to water stress through complex hydraulic and growth adjustments, with its recovery capacity being a key component of drought tolerance. Recurrent drought can induce an acquired "water stress memory" (priming), altering a genotype's response to future stress. We investigated whether drought responses in grapevine progenies are more shaped by genetic background or environmental history. Primed (NI) and non-primed (FI) progenies of two varieties: Trincadeira (isohydric) and Castelão (anisohydric) were exposed to well-watered (WW) and water stress (WS) conditions, followed by recovery. Over 2 weeks, we monitored plant water status, canopy growth, biomass, transpiration, hydraulic conductance, leaf gas-exchange, stomatal conductance kinetics, chlorophyll and wax content, and leaf temperature. Water stress increased root area only in FI progenies, whereas in NI progenies, fine root proliferation was more linked to past stress than to immediate water stress. Drought memory shifted NI plants towards a less conservative water-use strategy, with reduced water-use efficiency, higher stomatal conductance, and increased transpiration. In Trincadeira, priming enhanced circadian stomatal control, maximizing daytime opening and nighttime closure, while in Castelão it increased stomatal sensitivity to vapor pressure deficit. Leaf temperature differences between genetic backgrounds emerged earlier than stomatal conductance changes. Photosynthesis decline under WS was greater in FI than NI progenies, and primed plants recovered faster, indicating a compensatory recovery effect. Our results demonstrate that drought memory shifts plants towards a less conservative water-use strategy while ensuring photosynthetic capacity, confirming that long-term water stress induces a background memory in grapevine, which is transmitted across vegetatively propagated generations and enhances progeny responses to drought.