Open research questions in Horticultural and Viticultural Research

What the literature leaves open

• However, the grapevine rootstocks genetic control on conferred scion traits has rarely been explored and even less considering genetic diversity at the intra-species level through GWAS.

  Genome-wide association study of water-use efficiency and shoot biomass conferred by V. berlandieri rootstocks in grapevine · 2026 · DOI

• Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. © The Author(s) 2026 npj Science of Plants | (2026) 2:14 14

  The grapevine as a model plant to describe intra- and interspecific mechanisms of drought acclimation · 2026 · DOI

• Ogata, T. et al. CRISPR/Cas9-targeted mutagenesis of OsERA1 confers enhanced responses to abscisic acid and drought stress and increased primary root growth under nonstressed conditions in rice. PLoS ONE 15, e0243376 (2020). 115. de Melo, B. P. et al. Transcriptional modulation of AREB-1 by 116. CRISPRa improves plant physiological performance under severe water deficit. Sci. Rep. 10, 16231 (2020). Illouz-Eliaz, N. et al. Mutations in the tomato gibberellin receptors suppress xylem proliferation and reduce water loss under waterdeficit conditions. J. Exp. Bot. 71, 3603–3612 (2020). 117. Liu, L. et al. CRISPR/Cas9 targeted mutagenesis of SlLBD40, a lateral organ boundaries domain transcription factor, enhances drought tolerance in tomato. Plant Sci. 301, 110683 (2020). 118. Nuñez-Muñoz, L. et al. Plant drought tolerance provided through genome editing of the trehalase gene. Plant Signal. Behav. 16, 1877005 (2021). 119. Naing, A. H. & Kim, C. K. Abiotic stress-induced anthocyanins in plants: their role in tolerance to abiotic stresses. Physiol. Plant 172, 1711–1723 (2021). 133. Dal Santo, S. et al. The terroir concept interpreted through grape berry metabolomics and transcriptomics. J. Vis. Exp. 116, e54410 (2016). 134. Georgiadou, E. C. et al. The effect of terroir on volatilome fingerprinting and qualitative attributes of non-irrigated grapes reveals differences on glycosylated aroma compounds. J. Sci. Food Agric. 105, 507–519 (2025). 135. Palai, G. et al. Jasmonates signalling plays a key role in modulating berry terpenes accumulation under water deficit conditions in Vitis vinifera L. (cv. Sangiovese). Environ. Exp. Bot. 236, 106171 (2025). 136. Zarrouk, O. et al. Grape ripening is regulated by deficit irrigation/ elevated temperatures according to cluster position in the canopy. Front. Plant Sci. 7, 1640 (2016). 137. Pinasseau, L. et al. Cultivar diversity of grape skin polyphenol composition and changes in response to drought investigated by LC-MS based metabolomics. Front. Plant Sci. 8, 1826 (2017). 138. Schefeldt, P. & Hrazdina, G. Co-pigmentation of anthocyanins under physiological conditions. J. Food Sci. 43, 517–520 (1978). 120. Tu, M. et al. CRISPR/Cas9-mediated mutagenesis of VvbZIP36 promotes anthocyanin accumulation in grapevine (Vitis vinifera). Hortic. Res. 9, uhac022 (2022). 139. Rustioni, L. et al. Copigmentation and anti-copigmentation in grape extracts studied by spectrophotometry and post-column-reaction HPLC. Food Chem. 132, 2194–2201 (2012). 121. Reta, K. et al. Canopy management practices in warm environment vineyards to improve grape yield and quality in a changing climate. A review. A vademecum to vine canopy management under the challenge of global warming. Sci. Hortic. 341, 113998 (2025). 122. Beusa, I. et al. Delaying berry ripening of Bobal and Tempranillo grapevines by late leaf removal in a semi-arid and temperate-warm climate under different water regimes. Aust. J. Grape Wine Res.

  The grapevine as a model plant to describe intra- and interspecific mechanisms of drought acclimation · 2026 · DOI

• of Cabernet Sauvignon and Chardonnay. BMC Genom. 10, 212 (2009). 72. Corso, M. et al. Comprehensive transcript profiling of two grapevine rootstock genotypes contrasting in drought susceptibility links the phenylpropanoid pathway to enhanced tolerance. J. Exp. Bot. 66, 5739–5752 (2015). 93. 94. Arias, P. et al Climate change 2021: the physical science basis. IPCC AR6 WG1 Technical Summary, https://www.ipcc.ch/report/ar6/ wg1/downloads/report/IPCC_AR6_WGI_TS.pdf (2021). Schönbeck, L. C. et al. Increasing temperature and vapour pressure deficit lead to hydraulic damages in the absence of soil drought. Plant, Cell Environ. 45, 3275–3289 (2022). 73. Chitarra, W. et al. Drought stress and the effectiveness of 95. Cabodevilla, A. et al. Bunch transpiration is involved in the transcriptomics in identifying drought tolerance mechanisms in plants. in Exogenous Priming and Engineering of Plant Metabolic and Regulatory Genes, 389–402 (Academic Press, 2025). Sandrini, M. et al. Microbe-assisted crop improvement: a sustainable weapon to restore holobiont functionality and resilience. Hortic. Res. 9, uhac160 (2022). 74. hastening of grape berry ripening under elevated temperature and low relative humidity conditions. Plant Physiol. Biochem. 206, 108258 (2024). Rienth, M. et al. Day and night heat stress trigger different transcriptomic responses in green and ripening grapevine (Vitis vinifera) fruit. BMC Plant Biol. 14, 108 (2014). 96. 75. Marasco, R. et al. Are drought-resistance promoting bacteria cross- 97. Cochetel, N. et al. Drought tolerance of the grapevine, Vitis champinii 76. compatible with different plant models?. Plant Signal. Behav. 8, e26741 (2013). Pacifico, D. et al. The role of the endophytic microbiome in the grapevine response to environmental triggers. Front. Plant sci. 10, 1256 (2019). 77. Nerva, L. et al. Mycorrhizal symbiosis balances rootstockmediated growth-defence tradeoffs. Biol. Fertil. Soils 58, 17–34 (2022). Rolli, E. et al. Improved plant resistance to drought is promoted by the root-associated microbiome as a water stress-dependent trait. Environ. Microbiol. 17, 316–331 (2015). Trouvelot, S. et al. Arbuscular mycorrhiza symbiosis in viticulture: a review. Agron. Sustain. Dev. 35, 1449–1467 (2015). Balestrini, R. & Lumini, E. Focus on mycorrhizal symbioses. Appl. soil Ecol. 123, 299–304 (2018). 78. 79. 80. cv. Ramsey, is associated with higher photosynthesis and greater transcriptomic responsiveness of abscisic acid biosynthesis and signaling. BMC Plant Biol. 20, 55 (2020). 98. Hewitt, S. et al. Impact of heat stress, water stress, and their 99. combined effects on the metabolism and transcriptome of grape berries. Sci. Rep. 13, 9907 (2023). Braidotti, R. et al. Multi-hormonal analysis and aquaporins regulation reveal new insights on drought tolerance in grapevine. J. Plant Physiol. 296, 154243 (2024). 100. Arrizabalaga, M. et al.

  The grapevine as a model plant to describe intra- and interspecific mechanisms of drought acclimation · 2026 · DOI

• 31. 32. 33. 34. 35. 36. 37. Perrone, I. et al. The grapevine root-specific aquaporin VvPIP2;4N controls root hydraulic conductance and leaf gas exchange under well-watered conditions but not under water stress. Plant Physiol. 160, 965–977 (2012). Lamarque, L. J. et al. Quantifying the grapevine xylem embolism resistance spectrum to identify varieties and regions at risk in a future dry climate. Sci. Rep. 13, 7724 (2023). Lens, F. et al. Functional xylem characteristics associated with drought-induced embolism in angiosperms. N. Phytol. 236, 2019–2036 (2022). Bouda, M. et al. In vivo pressure gradient heterogeneity increases flow contribution of small diameter vessels in grapevine. Nat. Commun. 10, 5645 (2019). Sorek, Y. et al. An increase in xylem embolism resistance of grapevine leaves during the growing season is coordinated with stomatal regulation, turgor loss point and intervessel pit membranes. N. Phytol. 229, 1955–1969 (2021). Brodersen, C. R. et al. In vivo visualizations of drought-induced embolism spread in Vitis vinifera. Plant Physiol. 161, 1820–1829 (2013). Lovisolo, C. et al. An abscisic acid-related reduced transpiration promotes gradual embolism repair when grapevines are rehydrated after drought. N. Phytol. 180, 642–651 (2008). 38. Morabito, C. et al. Do the ends justify the means? Impact of drought progression rate on stress response and recovery in Vitis vinifera. Physiol. Plant 174, e13590 (2022). 39. Morabito, C. et al. Grapevine adopts different strategies in response to drying regimes. Procrastinator or escaper?. J. Plant Physiol. 314, 154622 (2025). Vuerich, M. et al. Contrasting responses of two grapevine cultivars to drought: the role of non-structural carbohydrates in xylem hydraulic recovery. Plant Cell Physiol. 64, 920–932 (2023). 40. 41. Chitarra, W. et al. Gene expression in vessel-associated cells upon xylem embolism repair in Vitis vinifera L. petioles. Planta 239, 887–899 (2014). Schuldt, B. et al. Revisiting paradigms related to root hydraulic limitation under drought. in Progress in Botany (Springer, 2025). 42. 43. Obiero, C. O., Keller, M. Apparent hydraulic strategies of diverse 44. winegrape cultivars depend on the choice of driving and response variables, part A: leaf water status. BMC Plant Biol. 26, 455 (2025). Zufferey, V. et al. Diurnal cycles of embolism formation and repair in petioles of grapevine (Vitis vinifera cv. Chasselas). J. Exp. Bot. 62, 3885–3894 (2011). 45. Charrier, G. et al. Evidence for hydraulic vulnerability segmentation and lack of xylem refilling under tension. Plant Physiol. 172, 1657–1668 (2016). 46. Hochberg, U. et al. Grapevine petioles are more sensitive to drought induced embolism than stems: evidence from in vivo MRI and microcomputed tomography observations of hydraulic vulnerability segmentation. Plant Cell Environ. 39, 1886–1894 (2016). Shelden, M. C. et al.

  The grapevine as a model plant to describe intra- and interspecific mechanisms of drought acclimation · 2026 · DOI

• and ABA- or JA-dependent pathways emerge as promising candidates, but only a few have been validated under fluctuating field conditions. This knowledge gap limits the use of NPBTs for climate resilience without risking pleiotropic or undesirable effects on wine typicity. Third, the grapevine microbiome, encompassing root-associated bacteria, fungi, and viruses, has emerged as an active determinant of stress acclimation with the ability to modulate hormonal balances, antioxidant defences, and osmotic adjustment, particularly in drought-sensitive genotypes. However, microbial contributions are highly context-dependent, and robust strategies to integrate microbiome-mediated resilience into viticultural practice are still lacking. Advancing this field will require combining metagenomics, transcriptomics, and metabolomics with vineyardscale inoculation trials to translate the microbiome potential into reproducible outcomes. Finally, stress memory and epigenetic regulation, though increasingly recognized as pivotal in the acclimation of perennial species, remain poorly characterized in grapevine. Preliminary evidence suggests that drought can induce shifts in DNA methylation and transgenerational priming of polyphenolic metabolism, but the molecular underpinnings and ecological relevance of these phenomena are still largely speculative. Clarifying how memory and holobiont dynamics intersect could open new avenues for breeding and for designing more sustainable vineyard systems. Altogether, grapevine offers an unparalleled opportunity to bridge physiology, molecular genetics, and agroecology in the study of drought resilience (Fig. 4). Future research should prioritize integrative, multi-omics approaches embedded in realistic vineyard contexts, explicitly considering multi-stress scenarios in which drought co-occurs with heatwaves and pathogen pressure. Adopting a holobiont-centred and long-term perspective will not only refine our understanding of grapevine acclimation but also provide transferable insights for other woody crops, reinforcing viticulture’s leading role at the forefront of climate-smart agriculture.

  The grapevine as a model plant to describe intra- and interspecific mechanisms of drought acclimation · 2026 · DOI

• 35 °C threshold, conditions often associated with drought, further promote anthocyanin acylation127,128. However, knowledge about acyltransferase in grapevine remains limited. Although BAHD-AT129, VvGAT1, VvSCP5 and VvSCP31130 have been identified as candidate acyltransferase-encoding genes involved in anthocyanin acylation, no functional studies have yet demonstrated their direct regulation by water availability or relation to the degree of drought adaptation in specific genotypes. Increasing anthocyanin molecular weight through tri-hydroxylation, methylation and acylation leads to variations in must and wine colour and influences wine stability during aging. The fine chemical analyses of individual polyphenols further reveal that many phenylpropanoid accumulation patterns are cultivarspecific, and thus, clearly under strong genetic control. For instance, the combination of high temperatures and drought has been shown to increase concentration, methylation, and acylation of anthocyanins in Tempranillo and Cabernet Sauvignon berries, but to cause only limited variations in Merlot and Grenache131, and no detectable change in Shiraz132. Beyond these clear genotype-dependent responses, cultivar adaptation to local environmental conditions, soils and cultural practices leads the same genotype to display distinct accumulation patterns of specific compounds. Such environmentally driven metabolic variation allows the production and definition of ‘Terroir’ wines. Two examples illustrate this point. First, the polyphenolic profiles of mature berries from a single Corvina clone collected across seven vineyards within the same vintage clearly separated the three macro-zones of origin, with peonidin-3-O-glucoside and acylated anthocyanins emerging as markers of berry provenance133. Second, the volatile organic compound (VOC) profiles of berries from own-rooted, non-irrigated Xynisteri vines grown in two different cultivation areas displayed notable variations at full ripeness, particularly in glycosylated monoterpenes and benzenic compounds; these metabolites are known to serve as key ‘flavour reservoir’ in wines134. In that study, factors such as adequate soil calcium availability, high clay content, low precipitation associated with elevated mean temperature, including a substantial number of days exceeding 35 °C, were associated with shifts in VOC concentration and profiles. In line with these observations, research has demonstrated that the distribution of JA and/or its derivatives, or the adoption of practices that increase endogenous JA, such as water deprivation before véraison135, increases the concentration of glycosylated monoterpenes, with potential implications for the aromatic quality of future wines. Chemical and enzymatic degradation patterns of secondary metabolites also reflect grapevine adaptation to drought.

  The grapevine as a model plant to describe intra- and interspecific mechanisms of drought acclimation · 2026 · DOI

• analyses show that AMF recruiting is enhanced in VvNPR3-edited Chardonnay lines, with a positive impact on performances under drought111. Beyond grapevine-specific breeding approaches, several candidate genes identified in other species112 could provide promising targets for improving water stress avoidance and tolerance in grapevine. For instance, the CRISPR/Cas9 system was successfully used in Arabidopsis to create novel alleles of OPEN STOMATA 2 (OST2), a stomatal proton pump, and the resulting genome-edited lines displayed enhanced performances via altered stomatal closure under drought stress113. Another target acting at the stomatal level is the ENHANCED RESPONSE TO ABA1 (ERA1) gene, encoding the β-subunit of farnesyltransferase and regulating ABA signalling and dehydration responses. era1 mutant plants showed enhanced ABAinduced stomatal closure, making it a promising candidate for increasing drought tolerance in a variety of crops114. A further promising target is again related to ABA signalling: the overexpression of ABA-responsive elementbinding protein 1 (AREB1) improved Arabidopsis physiological performances under severe drought. This result was achieved by CRISPR activation (CRISPRa), a technique that could be potentially applied to other ABA-related genes for drought-targeted breeding strategies115. Targets outside the ABA pathway are also promising. In tomato, the editing of the GIBBERELLIN-INSENSITIVE DWARF1 (GID1) gibberellin receptor successfully reduced whole-plant transpiration under water-deficit conditions without impairing growth. Reduced gibberellin activity inhibited leaf growth, promoted stomatal closure, and reduced xylem vessel proliferation and expansion, therefore decreasing hydraulic conductivity and limiting water loss116. The jasmonate pathway also offers potential targets. The LATERAL ORGAN BOUNDARIES DOMAIN (LBD) transcription factors are plant-specific regulators of various processes, including organ development and response to stress. In tomato, LBD40 expression is jasmonatedependent and its CRISPR/Cas9 targeted mutagenesis improved drought tolerance by enhancing the water-holding capacity of the plant. Notably, grapevine is known to possess five LBD genes responsive to salt, mannitol, heat, and cold stresses117, making them promising candidates for genome editing aimed at multi-stress tolerance. An interesting gene target for enhancing tolerance mechanisms in anisohydric grapevine varieties is related to the trehalose catabolic pathway, given the osmoprotective role of this metabolite. Arabidopsis gene-edited mutants of TRE1, which encodes the trehalase enzyme responsible for trehalose hydrolysis, exhibited enhanced drought tolerance118. Finally, the accumulation of anthocyanins, key metabolites that contribute both to grapevine berry quality and defence responses, is known to confer tolerance to various abiotic stresses in multiple plant species119.

  The grapevine as a model plant to describe intra- and interspecific mechanisms of drought acclimation · 2026 · DOI

• Fig. 4 | Schematic summary of the multi-layered investigative approaches underway aimed at optimizing grapevine responses to drought. This scheme summarizes three complementary layers of grapevine responses and improvement strategies. On the left, the root-associated microbiome enhances tolerance through multiple processes, including bacterial ACC deaminase activity that lowers stressinduced ethylene, while arbuscular mycorrhizal fungi (AMF) that mitigate oxidative stress, collectively sustaining ABA biosynthesis and activating stress-responsive transcriptional networks (e.g., WRKY, MYB, GRAS). These responses promote the accumulation of protective metabolites such as stilbenes, flavonols, phenylpropanoids, soluble sugars, and proline. In the centre, plant-intrinsic acclimation involves drought- and heat-induced modulation of secondary metabolism, including the activation of the phenylpropanoid pathway (VvCHS, VvUFGT, VvF3’5’H, VvOMT), stilbene biosynthesis, and acyltransferase-driven anthocyanin acylation (VvGAT1, VvSCP5, VvSCP31), alongside cultivar-specific alterations in flavonol profiles. On the right, conventional breeding is constrained by the need to preserve historical cultivars, whereas New Plant Breeding Techniques (NPBTs) including genome editing can specifically target traits such as stomatal behaviour (VvEPF9-1, OST2, GID1), biochemical and hormonal responses (VvGST40, VvbZIP36, ERA1, AREB1, TRE1, LBD), and microbial recruitment (VvNPR3). This integrative view highlights how combining plant physiology, microbial symbioses, and biotechnology can advance sustainable viticulture under climate change. conclusions. Genotypes identified as resilient under drought alone may fail when heat waves coincide with water scarcity, which represents the actual selective pressure faced in Mediterranean vineyards. Ignoring this simultaneity risks overlooking germplasm that is well adapted to real-world field conditions. Finally, framing viticulture through a Mediterranean lens offers a unifying conceptual structure. It connects environmental constraints, plant physiological responses, and berry metabolic outcomes into a coherent system, providing a basis for predictive approaches. This shift toward mechanistic integration is essential for forecasting cultivar performance, guiding the selection of resilient plant material, and ensuring the long-term sustainability of viticulture in a rapidly changing climate23. In this context, understanding how grapevines perceive, regulate, and ultimately adapt to water deficit becomes central, as drought responses constitute the physiological backbone upon which resilience to more complex Mediterranean stress scenarios is built. Exploitable target genes in breeding approaches aimed at improving avoidance/tolerance to water stress The viticultural agro-ecosystem is seriously impacted by climate-changeinduced abiotic stresses and by the intensification of fungal diseases101.

  The grapevine as a model plant to describe intra- and interspecific mechanisms of drought acclimation · 2026 · DOI

• context-specific microbial functions. Mechanistically, beneficial microorganisms enhance grapevine resilience to water deficit in several ways. They fine-tune hormonal balances, for instance by reducing stress-induced ethylene through ACC deaminase activity, thereby sustaining root growth and water uptake under limiting conditions. They also promote the accumulation of compatible solutes such as proline and soluble sugars, strengthening osmotic adjustment, and enhancing antioxidant defences through the accumulation of superoxide dismutase, catalase, peroxidase and melatonin, which collectively mitigate oxidative damage. At the transcriptional level, microbial inoculation triggers a complex network of stressresponsive genes involved in ABA biosynthesis (e.g., VvNCED1), proline and sugar metabolism, and the phenylpropanoid pathway, while activating signalling cascades mediated by WRKY, MYB, and GRAS transcription factors. In addition, AMF have been shown to influence small RNA regulation (e.g., the miR156/miR529/miR535 superfamily) and secondary metabolism, stimulating the production of flavonoids and stilbenes with recognized antioxidant and protective functions81. Collectively, these findings underscore the importance of integrating plant–microbe interactions into grapevine drought acclimation studies: the microbiome is not merely a passive passenger but an active co-determinant of host stress responses. The grapevine biological platform also provides opportunities to explore long-term acclimation strategies, including stress memory and transgenerational effects in woody crops. Evidence suggests that recurrent drought exposure can prime grapevine physiological and molecular responses, leading to faster or stronger activation of protective mechanisms upon subsequent stress events. Such stress imprinting may involve epigenetic modifications, metabolic reallocation, and shifts in microbiome composition that persist beyond a single stress episode. In particular, epigenetic mechanisms have emerged as major players contributing to the primed state of plants after stress exposure82. The study by Rodriguez- Izquierdo et al83. conducted on cultivated and wild accessions of Vitis, provides evidence of genome-wide differential methylation related to stressresponse and metabolic pathways in Vitis. Other recent studies have also addressed the epigenetic adaptive capacities of vines in relation to different environments84–86, under different possible stressors, as reviewed by Tan and Rodríguez López87. Understanding how the processes underlying stress memory operate in grapevine could reveal new targets for enhancing resilience to abiotic stress88–90.

  The grapevine as a model plant to describe intra- and interspecific mechanisms of drought acclimation · 2026 · DOI

• the regulation of membrane aquaporins in perivascular cells, which increases cell permeability and accelerates water movement during the recovery phases of xylem embolism41. In rootstocks derived from Vitis rupestris, this aquaporin-mediated activity is closely associated with successful recovery from embolisms28. The decrease in water potential that triggers tolerance mechanisms also serves as an important signal for stomatal closure, as mentioned in the previous section. In this case, roots transmit hydraulic signals upward (decreasing the water potential of the entire plant system), while ABA can be synthesized locally in the leaves42. This makes it impossible to frame grapevine behaviour within a strict binary of isohydry versus anisohydry, as recently unequivocally demonstrated on 30 own-rooted winegrape cultivars originating from different European regions, tested in the same investigation site by Obiero and Keller43. Instead, stomatal control can be activated following a drop in water potential, with different vine species or cultivars responding more or less readily also depending on their genetics, rootstock and soil type4. The plant hydraulic system, especially in the root, thus becomes the first point of sensing for decreased water potential. Importantly, this sensitivity is not limited to the root tissues themselves: the root-soil interface can act as a critical control point. In this region, Schuldt et al. 42 emphasized the need to reconsider classical concepts of root xylem vulnerability (the “rootas-hydraulic-fuse” hypothesis). Their updated hypothesis proposes that hydraulic disconnection may instead originate at the root-soil interface, when the cortex shrinks during moderate soil drying, a situation commonly experienced by grapevines. Another “fuse” for controlling embolism damage, one that grapevines can sacrifice relatively easily, has often been identified in the leaf, through a mechanism leading to petiole abscission. This idea is the basis of the hydraulic segmentation hypothesis, according to which cavitation occurs at less negative water potentials in the petiole than in the stem44–47. Through this mechanism, the vine can tolerate substantial drops in water potential near the leaves. However, its effectiveness has recently been questioned by direct measurements in grapevine48,49. Indeed, growing evidence indicates that measurement artifacts have historically overestimated embolism vulnerability, suggesting that plants may not experience severe drought-induced embolism events under natural field conditions33,42,50. These considerations, now extended to all tree species, are supported by more than fifteen years of in vivo evidence collected by micro-CT technology across grapevine species and cultivars. In this field, in situ and in vivo demonstrations of intra- or inter-species-specific hydraulic tolerance factors during drought acclimationin grapevine is a benchmark of the literature on the subject51–61.

  The grapevine as a model plant to describe intra- and interspecific mechanisms of drought acclimation · 2026 · DOI

• Fig. 3 | Schematic summary of the main strategies for grapevine acclimation to water stress. This diagram illustrates contrasting isohydric (stress avoidance) and anisohydric (stress tolerance) mechanisms. Isohydric genotypes rely on rapid ABA biosynthesis, ABA/pH regulation, and stomatal closure to conserve water, with soil texture strongly influencing signal intensity. In contrast, anisohydric genotypes sustain transpiration under declining water potentials, relying on hydraulic signalling, osmotic adjustment, aquaporin activity, and embolism recovery. Differences in ABA sensitivity and metabolite accumulation highlight how genotype, soil conditions, and physiological trade-offs collectively shape drought acclimation and underpin grapevine’s role as a model for perennial crops. tolerance strategies correlate with deep reductions in water potential along the root-stem-leaf axis, which in turn promote xylem embolism. Grapevine has long been studied as a model species for understanding the control of xylem embolism6. Both passive resistance to embolism formation and efficient embolism repair have been suggested as key factors controlling anisohydric response behaviour (i.e., drought tolerance). In general, vessels with smaller diameters are less prone to embolism, whereas larger vessels, because of their greater lumen area and volume, are more susceptible to air seeding and bubble formation, processes that ultimately lead to embolization32. Recently, however, calls have been made for a more nuanced assessment of the vessel diameter-vulnerability relationship, to gain a better mechanistic understanding of the nanoscale biophysical processes that drive embolism initiation and spread33,34. This issue is particularly important in vineyard research, where a progressive acclimation to embolism is observed as the growing season advances35. Much of the literature on rootstocks and scions examines the anatomy of the xylem system, drawing on both traditional microscopic analyses and, more recently, on X-ray tomographic measurements (micro-CT)36. Furthermore, in grapevine, embolism recovery in the late afternoon or at night has been described as a common and effective mechanism37. Thus, biological control of the hydraulic system does not depend solely on avoiding embolism formation (which results from declining water potential and increasing hydrostatic tension in the xylem), but also on the ability to repair embolized vessels. Embolism recovery is based on two concurrent processes. The first is the transfer of osmoregulatory sugars from the phloem into the xylem, which draws water from the perivascular cells and the apoplast back into the embolized conduits. Recent studies have proposed a role for nonstructural carbohydrates (NSCs) in generating the osmotic pressure required for refilling38,39. Moreover, different cultivars appear to adopt distinct NSC-use strategies during drought: in ‘Grenache’, sucrose accumulation is closely associated with embolism formation and may help sustain refilling; in ‘Barbera’, NSCs may contribute to a conduit-recovery strategy via the formation of cell-wall hydrogels, which likely explain the reduction of conduit lumen detected by micro-CT40.

  The grapevine as a model plant to describe intra- and interspecific mechanisms of drought acclimation · 2026 · DOI

• Fig. 2 | Interrelationship between maximum daily stomatal conductance (gs) and corresponding minimum leaf water potential (midday ψleaf). The plot illustrates the two theoretical extremes: a pure ‘vertical’ response, representing complete drought avoidance and strictly isohydric behaviour (days 2–11, 2i–11i, red empty squares), in contrast with a pure ‘horizontal’ response, totally tolerant of continuous transpiration dissipation and descriptive of a strictly anisohydric behaviour (days 2–11, 2a–11a, red crosses). Intermediate situations between the two theoretical extremes are modelled to represent real cases, based on a meta-analysis of 718 data points from 26 different Vitis vinifera varieties investigated as scions, 15 non-V. vinifera rootstock genotypes and 11 own-rooted V. vinifera varieties. Linearised data were analysed using the univariate general linear model (GLM), following Lavoie- Lamoureux et al.4. In addition, other root-to-shoot signals complementary and synergistic to the ABA signal have been identified in grapevine, through exchange of miRNAs19 or small peptides20. Conversely, in hydraulic mechanisms, the turgor-driven water status of guard cells overrides hormonal signalling. In this case, stomatal regulation is linked to the declining leaf water potential, which may result from limited soil water availability, limited root absorption capacity, and/or xylem sys- tems with low hydraulic conductivity (e.g. high incidence of embolism). The drop in leaf water potential also triggers local ABA biosynthesis, which supports stomatal closure long after the initial hydraulic signal21. This hydraulic signal, which directly induces stomatal closure, will be discussed further in the next section. When stomata close, reduced transpiration helps conserve water, but the evaporative cooling system of the plant (its only mechanism for heat dissipation) loses effectiveness. As a result, severe water stress accompanied by prolonged stomatal closure causes physiological dysfunction due to leaf overheating. In many wine-growing regions worldwide, water stress thus leads to heat stress22, also because arid envir- onments are often simultaneously hot23. How does the vine defend itself? The response involves a complex interplay of photorespiration and pho- toinhibition. In short: high temperatures in the chloroplast shift Rubisco activity toward oxygenation rather than carboxylation. This means the diversion of ribulose-6-phosphate into C2 compounds that enter the pho- torespiratory pathway, instead of C3 intermediates used for the biosynthesis of primary sugars in the Calvin-Benson cycle. Photorespiration consumes ATP and dissipates excess energy, an important function when high light adds to heat. Since the sun is the source of both heat and light, photo- respiration acts as a safety mechanism protecting the leaf from photo- inhibition (often irreversible). Protection against photoinhibition also relies on photoprotective and antioxidant systems.

  The grapevine as a model plant to describe intra- and interspecific mechanisms of drought acclimation · 2026 · DOI

• Fig. 1 | Theoretical kinetics of stomatal conductance (gs) and leaf water potential (ψleaf) over 10 days of absence of water supply under optimal transpiration conditions. a from day 2 to day 11 the grapevine exhibits a response dominated by stomatal control, which allows to maintain an isohydric leaf status (stable midday Ψ leaf and slight progressive decline in the predawn values). This is the theoretical representation of a pure drought avoidance response. b from day 2 to day 11 the plant shows a progressive activation of osmotic adjustment, leading to lower midday Ψ leaf, sustained transpirational dissipation, and a pronounced reduction in predawn Ψ leaf, reflecting the gradual depletion of soil water. This is the theoretical representation of a pure drought tolerance response. In grapevine, these two behaviours have not evolved as mutually exclusive but rather as coexisting strategies. The broad platform provided by cultivars and rootstocks adapted to diverse climates has produced a continuous gradient between avoidance and tolerance mechanisms9. By plotting the maximum gs values and the minimum daily leaf water potential (midday Ψ leaf) over the ten days of the incipient-drought kinetics described in Fig. 1, it becomes possible to visualize this continuum. On one end lies a strictly ‘vertical’ response, representing the theoretical response of complete avoidance and a purely isohydric behaviour (days 2i–11i). On the opposite end is a strictly ‘horizontal’ response, fully tolerant of continuous transpirative dissipation, corresponding to a purely anisohydric behaviour (days 2a–11a) (Fig. 2). In a meta-analysis describing the factors governing stomatal conductance in relation to water availability4, realworld behaviours consistently fall between these two extremes: more vertical when the plant is more evasive (i.e. a stress avoider), and more horizontal when it is more tolerant. Main mechanisms controlling water stress avoidance in grapevine The definitive mechanism for avoiding water stress is stomatal closure. For decades, grapevine has served as a strong model for how stomatal control is regulated through both ABA-mediated and hydraulic factors10. The ABA pathway exemplifies i) root-to-shoot signalling via the xylem, ii) chemical modulation of hormonal signals, iii) foliar regulation of signal intensity, and iv) stomatal sensitivity to the transmitted signal. i. The root biosynthesizes ABA when its water potential declines, that is, when water in the soil, and therefore at the soil-root interface, becomes progressively less available11. Rootstocks that strongly induce stomatal closure synthesize ABA at less negative potentials than those associated with anisohydric regulation (tolerant rootstocks, see next paragraph).

  The grapevine as a model plant to describe intra- and interspecific mechanisms of drought acclimation · 2026 · DOI

• The grapevine as a model plant to describe intra- and interspecific mechanisms of drought acclimation https://doi.org/10.1038/s44383-026-00028-6 Claudio Lovisolo1, Irene Perrone2, Walter Chitarra2,3, Luca Nerva3 & Alessandra…

  The grapevine as a model plant to describe intra- and interspecific mechanisms of drought acclimation · 2026 · DOI

• This study highlights the role of rootstock–scion interactions in shaping grapevine responses to controlled water deficit, revealing genotype-dependent differences in early molecular responsiveness across grafting combinations. Differences in transcriptional responses suggest that combinations vary in their molecular sensitivity to water limitation. Coordinated modulation of hormonal Maggiolini et al. BMC Plant Biology (2026) 26:891 Page 18 of 20 signaling, aquaporins, phenylpropanoid metabolism, and cytoskeletal components indicates the complexity of regulatory networks underlying early water-deficit responses. Notably, the combined modulation of cytoskeletal genes and aquaporins represents a relatively underexplored aspect of scion–rootstock interactions under reduced water availability. Unlike most previous studies focusing on established cultivars, this work evaluates newly selected table grape genotypes across different rootstock combinations during early selection stages. The candidate genes identified (Table 2; Supplementary Figs. 5 and 6) represent potential molecular markers for discriminating scion– rootstock combinations based on their sensitivity to reduced irrigation, providing a useful framework for breeding programs aimed at optimizing table grape performance under moderate water limitation. Notably, the two scion genotypes displayed distinct transcriptional responsiveness patterns: Maula generally showed stronger transcriptional reprogramming under reduced irrigation, whereas Genusia exhibited comparatively moderated responses. These results suggest that scion– rootstock combinations may differ in their molecular sensitivity thresholds to irrigation reduction. More broadly, this study shows how transcriptomic profiling can complement physiological screening to support early evaluation of scion–rootstock combinations in table grape breeding. Future studies integrating transcriptomic data with physiological analyses and field validation will be essential to support the development of climate-resilient grapevine cultivars under variable water availability. number of enriched genes. Supplementary Material 4: Supplementary Figure 4. Gene Ontology enrichment between genotypes. A. GO enrichment analysis of DEGs at WS in Maula compared to Genusia grafted on 1103P; B. GO enrichment analysis of DEGs at WS in Maula compared to Genusia grafted on SO4. For each functional category (BP= Biological process; CC=Cellular component; MF= molecular function) Down-regulated genes and up-regulated genes are reported by green and red bars respectively. The length of each bar is proportional to the number of enriched genes. Supplementary Material 5: Supplementary Figure 5. Plant hormone signalling pathway- vvi04075.

  Scion-Rootstock interactions shape early transcriptional responses to controlled water deficit in newly selected table grape genotypes · 2026 · DOI

• A severe overwinter frost between 2021 and 2022 caused 95% reproductive bud mortality and markedly altered soil N dynamics (20–26% increase in total N, 77–106% increase in biological N availability in 0–30 cm layer). Future studies should systematically investigate the mechanisms and magnitude of frost-induced root mortality, freeze-thaw cycle effects on N immobilization in microbial biomass, and sap bleeding contributions to labile N pools using 15N isotope tracing across multiple freeze-thaw cycles.

  Rapid fertilizer turnover and dominant soil N mineralization in a cool-climate vineyard revealed by 15N tracing, biological N availability, and N exposure · 2026 · DOI

• This study was conducted at a low vine density of 2,778 vines·ha−1, but a meta-analysis reported mean viticulture density of 3,800 vines·ha−1 with values ranging from 1,250 to 10,000 vines·ha−1. The effects of vine density on N export per hectare and fertilizer NUE need to be evaluated across denser vineyard plantings using the same 15N tracing methodology to determine if N removal and mineralization patterns scale proportionally.

  Rapid fertilizer turnover and dominant soil N mineralization in a cool-climate vineyard revealed by 15N tracing, biological N availability, and N exposure · 2026 · DOI

• The N balance quantification revealed ~71% of applied fertilizer N as unaccounted for in the N25 treatment, partitioned between roots, soil organic matter, and apparent losses from the 0–50 cm profile. Direct measurement of N retained in root systems and quantification of N leached to deeper soil layers (>50 cm) is needed to distinguish actual environmental losses (denitrification, NH3 volatilization) from downward N mobility in cool-climate vineyards.

  Rapid fertilizer turnover and dominant soil N mineralization in a cool-climate vineyard revealed by 15N tracing, biological N availability, and N exposure · 2026 · DOI

• The mechanism by which GA3 application induces early fruit set and cell expansion leading to berry size enlargement in 'Rizamat' cultivars has not been investigated at the cellular or hormonal level, particularly regarding interactions with other phytohormones during fruit development.

  Effect of Applying GA3 Treatment on Vitis vinifera Agronomical Traits and Embryo Germination Rate · 2026 · DOI

• The paper reports that optimal embryo growth was observed only in untreated grape clusters, but does not investigate whether post-treatment application of growth regulators or modified in vitro culture media could rescue embryo viability in GA3-treated rudiments.

  Effect of Applying GA3 Treatment on Vitis vinifera Agronomical Traits and Embryo Germination Rate · 2026 · DOI

• The embryo rescue method was only applied to three cultivars ('Rizamat', 'Toyfi', 'Qora Kishmish'); the generalizability of GA3-induced seedlessness effects and embryo germination rates to other seeded and seedless Vitis vinifera cultivars grown under different environmental conditions requires validation.

  Effect of Applying GA3 Treatment on Vitis vinifera Agronomical Traits and Embryo Germination Rate · 2026 · DOI

• While the study identifies that high GA3 concentrations completely destroyed rudiments in both seeded and seedless varieties, the dose-response relationship and optimal GA3 concentration threshold for balancing fruit set and berry enlargement without compromising embryo viability across different Vitis vinifera cultivars has not been characterized.

  Effect of Applying GA3 Treatment on Vitis vinifera Agronomical Traits and Embryo Germination Rate · 2026 · DOI

• The study demonstrates that GA3 application before flower cup induces seedlessness and embryo abortion, but the specific molecular mechanisms underlying GA3-induced embryo viability loss in both seeded ('Rizamat') and seedless ('Toyfi', 'Qora Kishmish') cultivars remain unexplored. Investigation of GA signaling pathways and differential gene expression during GA3-induced embryo abortion is needed.

  Effect of Applying GA3 Treatment on Vitis vinifera Agronomical Traits and Embryo Germination Rate · 2026 · DOI

• ) native to the Americas are ecologically and culturally important plants that are also critical to the global cultivated grape industry as sources of traits for crop innovation, but many of these species are poorly documented and insufficiently conserved.

  Conservation gap analysis for wild grapevines ( <i>Vitis</i> L.) of the Americas · 2026 · DOI

Most-cited papers in Horticultural and Viticultural Research

• Grapevine pangenome facilitates trait genetics and genomic breeding · Nature Genetics · 2024 · 98 citations
• Defoliation alleviates cold-induced oxidative damage in dormant buds of grapevine by up-regulating soluble carbohydrates and decreasing ROS · Acta Physiologiae Plantarum · 2020 · 33 citations
• Seasonal growth and gas exchange of conventionally and minimally pruned Chardonnay canopies · Julius Kühn-Institut · 2026 · 23 citations
• Rootstocks increase grapevine tolerance to NaCl through ion compartmentalization and exclusion · Acta Physiologiae Plantarum · 2020 · 19 citations
• Chitosan Improves Morphological and Physiological Attributes of Grapevines Under Deficit Irrigation Conditions · Journal of Horticultural Research · 2021 · 18 citations
• Going organic in viticulture: a case-study comparison in Clare Valley, South Australia · Australasian Journal of Environmental Management · 2011 · 8 citations
• Exchange of Total Carbohydrate, Minerals, and Phenolics in Grape and Grape Products · Turkish Journal of Agriculture - Food Science and Technology · 2021 · 8 citations
• Effects of intercropping medicinal and aromatic plants (MAPs) on grapevine cv. Sangiovese berry volatile compounds · Agroecology and Sustainable Food Systems · 2022 · 8 citations
• CAPITALIZATION OF SECONDARY WINE PRODUCTS - AN OPPORTUNITY FOR THE WINE SECTOR OF REPUBLIC OF MOLDOVA AND ROMANIA · Journal of Social Sciences · 2021 · 7 citations
• Effects of constantly high soil water content on vegetative growth and grape quality in Japan with high rainfall during grapevine growing season · Folia Horticulturae · 2020 · 7 citations

Most recent work

• Seasonal growth and gas exchange of conventionally and minimally pruned Chardonnay canopies · Julius Kühn-Institut · 2026
• Enhancing the yield and berry color of crimson seedless table grape variety (Vitis vinifera L.) via zinc oxide nanoparticles integrated with molasses · BMC Plant Biology · 2026
• Evolutionary forecast of vineyard yield in a mediterranean climate: A multi-temporal machine learning approach in Cádiz, Spain · Precision Agriculture · 2026
• Genome-wide association study of water-use efficiency and shoot biomass conferred by V. berlandieri rootstocks in grapevine · BMC Plant Biology · 2026
• Scion-Rootstock interactions shape early transcriptional responses to controlled water deficit in newly selected table grape genotypes · BMC Plant Biology · 2026
• Effect of Applying GA3 Treatment on Vitis vinifera Agronomical Traits and Embryo Germination Rate · Advances in Biology & Earth Sciences · 2026
• Conserved stomatal regulation across winegrape cultivars challenges conclusions regarding hydraulic strategies · BMC Plant Biology · 2026
• Agro-morphological Characterization of Two Grape Varieties (Aleatico and Bequignol) of Vines [Vitis vinifera] L. (Vitaceae)] in a Nursery in Daloa, Côte d’Ivoire · Annual Research & Review in Biology · 2026
• Rapid fertilizer turnover and dominant soil N mineralization in a cool-climate vineyard revealed by 15N tracing, biological N availability, and N exposure · Biology and Fertility of Soils · 2026
• Effect of training systems on spring frost tolerance of ‘Thompson Seedless’ grapevine · BMC Plant Biology · 2026

Related topics in Agricultural and Biological Sciences