Pit Membrane Thickness Determines Differences in Embolism Resistance Among Brassica oleracea Genotypes N. Anai Pereira‐Zaldívar, Giovanni Bortolami, Maximilian Larter, Sylvain Delzon, Régis Burlett, et al. Physiologia Plantarum, 2026 As drought events become more severe, understanding drought‐tolerance traits in crops is vital for food security. Brassica oleracea L., a widely consumed vegetable (including cabbage, cauliflower, and broccoli), has seen a rise in cultivation, but the response of different genotypes to drought remains poorly studied. Here, we investigated the mechanisms underlying drought resistance in seven genotypes of B. oleracea (two grandparental lines and five F2 genotypes) by examining stem anatomical and hydraulic traits, as well as stomatal characteristics, leaf dimensions, and stomatal regulation under drought conditions. Detailed measurements of stem anatomical traits were obtained using light and electron microscopy, while stem hydraulic vulnerability was assessed using the Optical Vulnerability method. The seven genotypes displayed contrasting water‐use and hydraulic strategies. Under well‐watered conditions, initial stomatal conductance ( g sΨ0 ) showed considerable variation independent of their leaf and stomata size and density, while the leaf water potential at 90% stomatal closure ( Ψg s90 ) was similar among genotypes. Stomatal safety margins (SSM) were positive across genotypes, confirming coordination between stomatal regulation and xylem hydraulics, and mainly driven by stem P 50 , which was approximately 1 MPa lower in the most tolerant genotype. Embolism resistance was best explained by the thickness of the intervessel pit membrane, highlighting the importance of including anatomical traits in plant drought tolerance studies. To conclude, the intraspecific variation observed in anatomical, hydraulic and stomatal traits among our B. oleracea genotypes indicates potential adaptability to drought and suggests that more drought‐tolerant genotypes could be identified within this crop species through targeted, human‐mediated crosses.
Fungal Pathogen Activity and Stress-Dependent Responses of Grapevine Wood to Esca and Drought Marie Chambard, Dario Cantù, Giovanni Bortolami, Ninon Dell'Acqua, Nathalie Ferrer, et al. Physiologia Plantarum, 2026 Biotic and abiotic stresses alter the physiology of perennial plants, with consequences for fungal endophytes and disease expression. In grapevine, drought inhibits esca disease expression, but the underlying molecular interactions between the plant and fungi are unknown. We combined wood metatranscriptomics, metabolomics, and metabarcoding to investigate these interactions in 30‐year‐old grapevines and eight wood‐pathogenic fungi under conditions of drought or esca leaf symptom expression. Both esca and drought decreased grapevine transpiration, but with different underlying mechanisms that induced specific transcriptomic and metabolic signatures. Similar pathways were also activated, including the phenylpropanoid and stilbenoid synthesis pathways. These stress responses could potentially confer cross‐tolerance and elicit different fungal molecular responses. Across all fungi, the total level of putative virulence factors increased significantly under both stresses. Under drought, only the relative abundance of Phaeomoniella chlamydospora and gene expression involved in anti‐oxidative mechanisms, growth, and reproduction increased. Under esca expression conditions, only the relative abundance of Fomitiporia mediterranea and gene expression involved in wood degradation, competition, detoxification, and growth increased. Under drought, induced grapevine defenses and reduced transpiration, together with the low abundance and putatively weak virulence of F. mediterranea may account for the inhibition of esca leaf symptom.
Hydraulic stress limits thermal acclimation in trees under chronic drought Alyssa T. Kullberg, Arianna Milano, Alvaro Poretti, Yike Ma, Patrick Favre, et al. Proceedings of the National Academy of Sciences of the United States of America, 2026 The capacity of trees to withstand intensifying hot drought events depends on the coordination between hydraulic safety and leaf thermoregulation, yet the limits of this coordination under chronic stress remain poorly understood. Here, we show that 5 y of chronic soil moisture limitation fundamentally constrains the capacity of leaves to maintain adequate thermoregulation. Focusing on two temperate tree species with contrasting water-use strategies, European beech ( Fagus sylvatica ) and downy oak ( Quercus pubescens ), which were subjected to a 5-y manipulation of soil moisture and air temperature, we tested how acclimation influences leaf thermoregulation, hydraulic safety margins (HSMs), thermal safety margins (TSMs), and leaf scorching. Under sustained heating with ample soil water availability, both species acclimated to maintain stable leaf temperature and positive TSMs despite warmer conditions, demonstrating that thermal acclimation is possible without hydraulic stress. By contrast, chronic soil drought narrowed HSMs and weakened evaporative cooling, reducing leaf thermoregulation capacity. When drought and heat co-occurred, stomatal closure triggered a runaway feedback loop: Impaired water transport led to loss of cooling, causing breaching of critical thermal thresholds. These events coincided with failures of photosystem II and scorching in drought-vulnerable beech, linking drought-induced stomatal limitation directly to thermal injury. Our results reveal that oak and beech can acclimate to warming alone, but not to simultaneous heat and drought, which together drive a hydraulic–thermal cascade exceeding both safety margins. This interaction sets fundamental limits on the resilience of temperate forests to future hot droughts.
Differential impacts of drought and esca expression on Ascomycota fungi in the trunks and young organs of mature grapevines Pierre Gastou, Giovanni Bortolami, Nathalie Ferrer, Gregory A. Gambetta, Samuele Moretti, et al. Phytobiomes Journal, 2025 Perennial plant decline is increasingly threatening the profitability and sustainability of agriculture and forestry worldwide. It results from intricate interactions between microbial communities, the plant host, and abiotic stressors. We investigated the effects of drought and esca disease on mature grapevine phytobiomes. Grapevines display no esca leaf symptoms during droughts, but the impacts of drought and esca expression on fungal communities and wood health in mature plants remain poorly understood. We studied 43 uprooted 30-year-old naturally infected vines in three experimental conditions: well-watered asymptomatic (Control) vines, vines with esca symptoms (Esca), and vines subjected to water deficit (WD) over two consecutive summers. We profiled trunk, cane, stem and petiole Ascomycota communities by DNA metabarcoding with primers specifically designed for grapevine trunk-associated Ascomycota, and quantified wood necrosis. The Ascomycota communities of trunks and younger organs clearly differed, and drought and esca had different impacts on the Ascomycota communities of perennial and young organs. In the trunk, drought significantly decreased fungal diversity in healthy wood and increased the abundance of wood pathogens (e.g. Phaeomoniella chlamydospora, Botryosphaeria dothidea). In young organs, esca expression decreased the species richness and diversity of the Ascomycota community to a greater extent than drought. We also found that the relative proportion of healthy wood was smaller in plants with esca symptoms than in control plants. Thus, drought increased Ascomycota pathogen abundance in the trunk but did not increase wood degradation and esca expression, highlighting the need to investigate the molecular basis of plant-microbiome interactions under multi-stress conditions.
Esca grapevine disease involves leaf hydraulic failure and represents a unique premature senescence process Giovanni Bortolami, Nathalie Ferrer, Kendra Baumgartner, Sylvain Delzon, David Gramaje, et al. Tree Physiology, 2023 Xylem anatomy may change in response to environmental or biotic stresses. Vascular occlusion, an anatomical modification of mature xylem, contributes to plant resistance and susceptibility to different stresses. In woody organs, xylem occlusions have been examined as part of the senescence process, but their presence and function in leaves remain obscure. In grapevine, many stresses are associated with premature leaf senescence inducing discolorations and scorched tissue in leaves. However, we still do not know whether the leaf senescence process follows the same sequence of physiological events and whether leaf xylem anatomy is affected in similar ways. In this study, we quantified vascular occlusions in midribs from leaves with symptoms of the grapevine disease esca, magnesium deficiency and autumn senescence. We found higher amounts of vascular occlusions in leaves with esca symptoms (in 27% of xylem vessels on average), whereas the leaves with other symptoms (as well as the asymptomatic controls) had far fewer occlusions (in 3% of vessels). Therefore, we assessed the relationship between xylem occlusions and esca leaf symptoms in four different countries (California in the USA, France, Italy and Spain) and eight different cultivars. We monitored the plants over the course of the growing season, confirming that vascular occlusions do not evolve with symptom age. Finally, we investigated the hydraulic integrity of leaf xylem vessels by optical visualization of embolism propagation during dehydration. We found that the occlusions lead to hydraulic dysfunction mainly in the peripheral veins compared with the midribs in esca symptomatic leaves. These results open new perspectives on the role of vascular occlusions during the leaf senescence process, highlighting the uniqueness of esca leaf symptoms and its consequence on leaf physiology.
Drought response in Arabidopsis displays synergistic coordination between stems and leaves Ajaree Thonglim, Giovanni Bortolami, Sylvain Delzon, Maximilian Larter, Remko Offringa, et al. Journal of Experimental Botany, 2023 The synergy between drought-responsive traits across different organs is crucial in the whole-plant mechanism influencing drought resilience. These organ interactions, however, are poorly understood, limiting our understanding of drought response strategies at the whole-plant level. Therefore, we need more integrative studies, especially on herbaceous species that represent many important food crops but remain underexplored in their drought response. We investigated inflorescence stems and rosette leaves of six Arabidopsis thaliana genotypes with contrasting drought tolerance, and combined anatomical observations with hydraulic measurements and gene expression studies to assess differences in drought response. The soc1ful double mutant was the most drought-tolerant genotype based on its synergistic combination of low stomatal conductance, largest stomatal safety margin, more stable leaf water potential during non-watering, reduced transcript levels of drought stress marker genes, and reduced loss of chlorophyll content in leaves, in combination with stems showing the highest embolism resistance, most pronounced lignification, and thickest intervessel pit membranes. In contrast, the most sensitive Cvi ecotype shows the opposite extreme of the same set of traits. The remaining four genotypes show variations in this drought syndrome. Our results reveal that anatomical, ecophysiological, and molecular adaptations across organs are intertwined, and multiple (differentially combined) strategies can be applied to acquire a certain level of drought tolerance.
Comparative anatomy vs mechanistic understanding: how to interpret the diameter-vulnerability link Frederic Lens, Sean M. Gleason, Giovanni Bortolami, Craig Brodersen, Sylvain Delzon, et al. IAWA Journal, 2023 Summary Results from comparative and ecological wood anatomy combined with a number of experimental studies on plant hydraulics have led to a pervasive and longstanding assumption that wider-diameter vessels are more vulnerable to drought-induced embolism than narrower vessels. Although we agree that wider vessels tend to be more vulnerable than narrower vessels within stems and within roots across most species, our current understanding of the diameter-vulnerability link does not offer a mechanistic explanation for why increased vessel diameter should consistently lead to greater vulnerability or vice versa. Causes of drought-induced embolism formation and spread likely operate at the nano-level, especially at gas-liquid-surfactant interfaces inside intervessel pit membranes. We evaluate here new perspectives on drought-induced embolism and its key anatomical and physico-chemical drivers, of which vessel diameter is one of the parameters involved, although its linkage to embolism vulnerability is likely indirect. As such, the diameter-vulnerability link does not imply that species with on average wider vessels are consistently more susceptible to drought-induced embolism compared to species with narrower vessels. Scientific priorities for future progress should focus on more accurate predictions of how water transport in plants is affected by drought, which requires a better mechanistic understanding of xylem network topology and biophysical processes at the nano-scale level in individual vessels that determine embolism formation and spread.
Functional xylem characteristics associated with drought-induced embolism in angiosperms Frederic Lens, Sean M. Gleason, Giovanni Bortolami, Craig Brodersen, Sylvain Delzon, et al. New Phytologist, 2022 Hydraulic failure resulting from drought-induced embolism in the xylem of plants is a key determinant of reduced productivity and mortality. Methods to assess this vulnerability are difficult to achieve at scale, leading to alternative metrics and correlations with more easily measured traits. Such efforts have led to the longstanding and pervasive assumed mechanistic link between vessel diameter and vulnerability in angiosperms. However, there are at least two problems with these assumptions that require critical re-evaluation: (1) our current understanding of drought-induced embolism does not provide a mechanistic explanation for why increased vessel width should lead to greater vulnerability, and (2) the most recent advancements in nano-scale embolism processes suggest that vessel diameter is not a direct driver. Here, we review data from physiological and comparative wood anatomy studies, highlighting the potential anatomical and physico-chemical drivers of embolism formation and spread. We then put forward key knowledge gaps, emphasising what is known, unknown, and speculation. A meaningful evaluation of the diameter-vulnerability link will require a better mechanistic understanding of the biophysical processes at the nano-scale level that determine embolism formation and spread, which will in turn lead to more accurate predictions of how water transport in plants is affected by drought.
Model-assisted ideotyping reveals trait syndromes to adapt viticulture to a drier climate Silvina Dayer, Laurent J Lamarque, Régis Burlett, Giovanni Bortolami, Sylvain Delzon, et al. Plant Physiology, 2022 Climate change is challenging the resilience of grapevine (Vitis), one of the most important crops worldwide. Adapting viticulture to a hotter and drier future will require a multifaceted approach including the breeding of more drought-tolerant genotypes. In this study, we focused on plant hydraulics as a multi-trait system that allows the plant to maintain hydraulic integrity and gas exchange rates longer under drought. We quantified a broad range of drought-related traits within and across Vitis species, created in silico libraries of trait combinations, and then identified drought tolerant trait syndromes. By modeling the maintenance of hydraulic integrity of current cultivars and the drought tolerant trait syndromes, we identified elite ideotypes that increased the amount of time they could experience drought without leaf hydraulic failure. Generally, elites exhibited a trait syndrome with lower stomatal conductance, earlier stomatal closure, and a larger hydraulic safety margin. We demonstrated that, when compared with current cultivars, elite ideotypes have the potential to decrease the risk of hydraulic failure across wine regions under future climate scenarios. This study reveals the syndrome of traits that can be leveraged to protect grapevine from experiencing hydraulic failure under drought and increase drought tolerance.
Grapevines under drought do not express esca leaf symptoms Giovanni Bortolami, Gregory A. Gambetta, Cédric Cassan, Silvina Dayer, Elena Farolfi, et al. Proceedings of the National Academy of Sciences of the United States of America, 2021
Fungal Pathogen Activity and Stress‐Dependent Responses of Grapevine Wood to Esca and Drought M Chambard, D Cantù, G Bortolami, N Dell'Acqua, N Ferrer, GA Gambetta, ... Physiologia Plantarum 178 (3), e70914 , 2026 2026
Hydraulic stress limits thermal acclimation in trees under chronic drought AT Kullberg, A Milano, A Poretti, Y Ma, P Favre, KM Johnson, G Bortolami, ... Proceedings of the National Academy of Sciences 123 (15), e2531865123 , 2026 2026
When trees run on savings: Stem water storage and rehydration as a missing link in drought responses RL Peters, A Buras, SA Grichting, M Schaub, C Grossiord, G Bortolami, ... EGU26 , 2026 2026
Differential impacts of drought and esca expression on Ascomycota fungi in the trunks and young organs of mature grapevines P Gastou, G Bortolami, N Ferrer, GA Gambetta, S Moretti, J Vallance, ... Phytobiomes Journal 10 (1), 57-71 , 2026 2026 Citations: 7
Effects of plant age and wood formation on drought tolerance in tomato A Pereira Zaldivar, G Bortolami, J Van den Bulcke, T Gheyle, I Josipovic, ... EGU General Assembly 2026 , 2026 2026
Decoupling of stomatal conductance from net assimilation at high temperature as a mechanism to increase transpiration P Schuler, M Didion-Gency, G Bortolami, T Julliard, G Hoch, C Bachofen, ... bioRxiv, 2025.11. 03.686201 , 2025 2025 Citations: 1
Esca Disease triggers local transcriptomic response and systemic DNA methylation changes in grapevine MMJ Berger, V Garcia, B Rubio, G Bortolami, G Gambetta, CEL Delmas, ... bioRxiv, 2025.08. 11.669596 , 2025 2025 Citations: 3
Fungal pathogen activity and stress-dependent responses of grapevine wood to esca and drought M Chambard, D Cantù, G Bortolami, N Dell’Acqua, N Ferrer, GA Gambetta, ... bioRxiv, 2025.08. 05.668645 , 2025 2025 Citations: 1
Stress-dependent responses of grapevine wood and fungal pathogen activity under esca and drought M Chambard, D Cantù, G Bortolami, N Dell’Acqua, N Ferrer, GA Gambetta, ... Cold Spring Harbor Laboratory , 2025 2025 Citations: 2
Tree functioning under different soil water availability and atmospheric water demand S Hunziker, J Gisler, R Peters, K Meusburger, R Zweifel, G Bortolami, ... ARPHA Conference Abstracts 8, e149040 , 2025 2025
VPDrought–a novel approach to disentangle atmospheric and soil drought in a natural Scots pine forest M Schaub, C Grossiord, G Bortolami, J Gisler, K Meusburger, P D’Odorico, ... ARPHA Conference Abstracts 8, e146958 , 2025 2025
High VPD mitigates the impact of soil drought in Pinus sylvestris L. through earlier stomatal closure G Bortolami, J Gisler, A Milano, M Schaub, R Peters, C Grossiord EGU General Assembly Conference Abstracts, EGU25-5661 , 2025 2025
Integrating gene expression analysis and ecophysiological responses to water deficit in leaves of tomato plants G Bortolami, TA de Werk, M Larter, A Thonglim, B Mueller-Roeber, ... Scientific Reports 14 (1), 29024 , 2024 2024 Citations: 5
Comparative anatomy vs mechanistic understanding: how to interpret the diameter-vulnerability link F Lens, SM Gleason, G Bortolami, C Brodersen, S Delzon, S Jansen IAWA Journal 44 (3-4), 368-380 , 2023 2023 Citations: 15
Effect of drought on grapevine wood fungal pathogen communities using a metatranscriptomics approach M Chambard, N Dell'Acqua, G Bortolami, D Cantu, N Ferrer, GA Gambetta, ... ICPP (12th International Congress Of Plant Pathology) , 2023 2023
One or the other: under drought, grapevines do not express esca leaf symptoms: Sourced from the research article:“Grapevines under drought do not express esca leaf symptoms … G Bortolami, GA Gambetta, CEL Delmas IVES Technical Reviews, vine and wine , 2023 2023
Esca grapevine disease involves leaf hydraulic failure and represents a unique premature senescence process G Bortolami, N Ferrer, K Baumgartner, S Delzon, D Gramaje, ... Tree Physiology 43 (3), 441-451 , 2023 2023 Citations: 21
Drought response in Arabidopsis displays synergistic coordination between stems and leaves A Thonglim, G Bortolami, S Delzon, M Larter, R Offringa, JJB Keurentjes, ... Journal of Experimental Botany 74 (3), 1004-1021 , 2023 2023 Citations: 22
L'un ou l'autre: en condition de sécheresse, la vigne n'exprime pas de symptômes foliaires d'esca G Bortolami, GA Gambetta, CEL Delmas IVES Technical Reviews, vigne et vin , 2023 2023 Citations: 3
One or the other: under drought, grapevines do not express esca leaf symptoms G Bortolami, GA Gambetta, CEL Delmas IVES Technical Reviews , 2023 2023
MOST CITED SCHOLAR PUBLICATIONS
Functional xylem characteristics associated with drought‐induced embolism in angiosperms F Lens, SM Gleason, G Bortolami, C Brodersen, S Delzon, S Jansen New Phytologist 236 (6), 2019-2036 , 2022 2022 Citations: 190
The sequence and thresholds of leaf hydraulic traits underlying grapevine varietal differences in drought tolerance S Dayer, JC Herrera, Z Dai, R Burlett, LJ Lamarque, S Delzon, ... Journal of Experimental Botany 71 (14), 4333-4344 , 2020 2020 Citations: 131
Exploring the hydraulic failure hypothesis of esca leaf symptom formation G Bortolami, GA Gambetta, S Delzon, LJ Lamarque, J Pouzoulet, E Badel, ... Plant physiology 181 (3), 1163-1174 , 2019 2019 Citations: 69
Grapevines under drought do not express esca leaf symptoms G Bortolami, GA Gambetta, C Cassan, S Dayer, E Farolfi, N Ferrer, ... Proceedings of the National Academy of Sciences 118 (43), e2112825118 , 2021 2021 Citations: 63
Nighttime transpiration represents a negligible part of water loss and does not increase the risk of water stress in grapevine S Dayer, JC Herrera, Z Dai, R Burlett, LJ Lamarque, S Delzon, ... Plant, Cell & Environment 44 (2), 387-398 , 2021 2021 Citations: 54
Seasonal and long-term consequences of esca grapevine disease on stem xylem integrity G Bortolami, E Farolfi, E Badel, H Burlett, Régis, Cochard, N Ferrer, ... Journal of Experimental Botany 72 (10), 3914–3928 , 2021 2021 Citations: 48
Model-assisted ideotyping reveals trait syndromes to adapt viticulture to a drier climate S Dayer, LJ Lamarque, R Burlett, G Bortolami, S Delzon, JC Herrera, ... Plant Physiology 190 (3), 1673-1686 , 2022 2022 Citations: 43
Drought response in Arabidopsis displays synergistic coordination between stems and leaves A Thonglim, G Bortolami, S Delzon, M Larter, R Offringa, JJB Keurentjes, ... Journal of Experimental Botany 74 (3), 1004-1021 , 2023 2023 Citations: 22
Esca grapevine disease involves leaf hydraulic failure and represents a unique premature senescence process G Bortolami, N Ferrer, K Baumgartner, S Delzon, D Gramaje, ... Tree Physiology 43 (3), 441-451 , 2023 2023 Citations: 21
Comparative anatomy vs mechanistic understanding: how to interpret the diameter-vulnerability link F Lens, SM Gleason, G Bortolami, C Brodersen, S Delzon, S Jansen IAWA Journal 44 (3-4), 368-380 , 2023 2023 Citations: 15
Understanding scion-rootstock interactions at the graft interface of grapevine SJ Cookson, D Prodhomme, C Chambaud, C Hevin, J Valls Fonayet, ... XII International Conference on Grapevine Breeding and Genetics 1248, 369-374 , 2018 2018 Citations: 8
Differential impacts of drought and esca expression on Ascomycota fungi in the trunks and young organs of mature grapevines P Gastou, G Bortolami, N Ferrer, GA Gambetta, S Moretti, J Vallance, ... Phytobiomes Journal 10 (1), 57-71 , 2026 2026 Citations: 7
Integrating gene expression analysis and ecophysiological responses to water deficit in leaves of tomato plants G Bortolami, TA de Werk, M Larter, A Thonglim, B Mueller-Roeber, ... Scientific Reports 14 (1), 29024 , 2024 2024 Citations: 5
Esca Disease triggers local transcriptomic response and systemic DNA methylation changes in grapevine MMJ Berger, V Garcia, B Rubio, G Bortolami, G Gambetta, CEL Delmas, ... bioRxiv, 2025.08. 11.669596 , 2025 2025 Citations: 3
L'un ou l'autre: en condition de sécheresse, la vigne n'exprime pas de symptômes foliaires d'esca G Bortolami, GA Gambetta, CEL Delmas IVES Technical Reviews, vigne et vin , 2023 2023 Citations: 3
Stress-dependent responses of grapevine wood and fungal pathogen activity under esca and drought M Chambard, D Cantù, G Bortolami, N Dell’Acqua, N Ferrer, GA Gambetta, ... Cold Spring Harbor Laboratory , 2025 2025 Citations: 2
Decoupling of stomatal conductance from net assimilation at high temperature as a mechanism to increase transpiration P Schuler, M Didion-Gency, G Bortolami, T Julliard, G Hoch, C Bachofen, ... bioRxiv, 2025.11. 03.686201 , 2025 2025 Citations: 1
Fungal pathogen activity and stress-dependent responses of grapevine wood to esca and drought M Chambard, D Cantù, G Bortolami, N Dell’Acqua, N Ferrer, GA Gambetta, ... bioRxiv, 2025.08. 05.668645 , 2025 2025 Citations: 1
Fungal Pathogen Activity and Stress‐Dependent Responses of Grapevine Wood to Esca and Drought M Chambard, D Cantù, G Bortolami, N Dell'Acqua, N Ferrer, GA Gambetta, ... Physiologia Plantarum 178 (3), e70914 , 2026 2026
Hydraulic stress limits thermal acclimation in trees under chronic drought AT Kullberg, A Milano, A Poretti, Y Ma, P Favre, KM Johnson, G Bortolami, ... Proceedings of the National Academy of Sciences 123 (15), e2531865123 , 2026 2026
