Hervé Cochard, Giovanni Bortolami, Jérôme Pouzoulet, Nathalie Ferrer, Régis Burlett, Santiago Trueba, Laurent J. Lamarque, Chloé E. L. Delmas, Andrew J. King, Gregory A. Gambetta, Elena Farolfi, Marie Marchesseau-Marchal, Sylvain Delzon, Eric Badel, José M. Torres-Ruiz, Pascal Lecomte, Santé et agroécologie du vignoble (UMR SAVE), Université de Bordeaux (UB)-Institut des Sciences de la Vigne et du Vin (ISVV)-Ecole Nationale Supérieure des Sciences Agronomiques de Bordeaux-Aquitaine (Bordeaux Sciences Agro)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Laboratoire de Physique et Physiologie Intégratives de l’Arbre en environnement Fluctuant (PIAF), Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Clermont Auvergne (UCA), Biodiversité, Gènes & Communautés (BioGeCo), Université de Bordeaux (UB)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Université du Québec à Trois-Rivières (UQTR), Ecophysiologie et Génomique Fonctionnelle de la Vigne (UMR EGFV), Yale University [New Haven], French Ministry of Agriculture, Agrifood, and Forestry (FranceAgriMer) within the PHYSIOPATH project (program Plan National Deperissement du Vignoble) / 22001150-1506, and ANR-10-EQPX-0016,XYLOFOREST,Plateforme d'Innovation ' Forêt-Bois-Fibre-Biomasse du Futur '(2010)
Hydraulic failure has been extensively studied during drought-induced plant dieback, but its role in plant-pathogen interactions is under debate. During esca, a grapevine (Vitis vinifera) disease, symptomatic leaves are prone to irreversible hydraulic dysfunctions but little is known about the hydraulic integrity of perennial organs over the short- and long-term. We investigated the effects of esca on stem hydraulic integrity in naturally infected plants within a single season and across season(s). We coupled direct (ks) and indirect (kth) hydraulic conductivity measurements, and tylose and vascular pathogen detection with in vivo X-ray microtomography visualizations. Xylem occlusions (tyloses) and subsequent loss of stem hydraulic conductivity (ks) occurred in all shoots with severe symptoms (apoplexy) and in more than 60% of shoots with moderate symptoms (tiger-stripe), with no tyloses in asymptomatic shoots. In vivo stem observations demonstrated that tyloses occurred only when leaf symptoms appeared, and resulted in more than 50% loss of hydraulic conductance in 40% of symptomatic stems, unrelated to symptom age. The impact of esca on xylem integrity was only seasonal, with no long-term impact of disease history. Our study demonstrated how and to what extent a vascular disease such as esca, affecting xylem integrity, could amplify plant mortality through hydraulic failure.