INRAE, BSA, ISVV, SAVE, 33882 Villenave d'Ornon, France.
Université Clermont-Auvergne, INRAE, PIAF, 63000 Clermont-Ferrand, France.
J Exp Bot. 2021 May 4;72(10):3914-3928. doi: 10.1093/jxb/erab117.
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.
水力衰竭在干旱引起的植物凋萎过程中已被广泛研究，但它在植物-病原体相互作用中的作用仍存在争议。在葡萄（Vitis vinifera）的 esca 病中，有症状的叶片容易出现不可逆转的水力功能障碍，但对多年生器官在短期和长期内的水力完整性知之甚少。我们在一个季节内和跨季节（多个季节）调查了 esca 对受感染植物茎部水力完整性的影响。我们将直接（ks）和间接（kth）水力传导率测量、木质部病原体和韧皮部病原体检测与体内 X 射线微断层扫描可视化相结合。木质部栓塞（木质部细胞）和随后的茎水力传导率（ks）丧失发生在所有有严重症状（中风）的芽中，并且在超过 60%有中度症状（虎纹）的芽中，无症状芽中没有木质部细胞。体内茎观察表明，木质部细胞仅在出现叶片症状时发生，并且导致 40%有症状茎中的水力传导率损失超过 50%，与症状年龄无关。esca 对木质部完整性的影响仅具有季节性，没有疾病史的长期影响。我们的研究表明，影响木质部完整性的血管疾病（如 esca）如何以及在何种程度上通过水力衰竭加剧植物死亡率。
