Esca grapevine disease involves leaf hydraulic failure and represents a unique premature senescence process

Area of Science:

• Plant anatomy and physiology
• Plant pathology
• Viticulture

Background:

• Vascular occlusions are known in woody organs during senescence but their role in leaves is unclear.
• Grapevine leaf senescence is often linked to stresses, but xylem anatomical changes remain poorly understood.
• The study investigates if leaf senescence follows similar physiological events and xylem modifications across different stress conditions.

Purpose of the Study:

• To quantify vascular occlusions in grapevine leaves under different stress conditions (esca, magnesium deficiency, autumn senescence).
• To assess the relationship between vascular occlusions and esca leaf symptoms across diverse geographical locations and cultivars.
• To investigate the impact of vascular occlusions on leaf xylem hydraulic integrity.

Main Methods:

• Quantification of vascular occlusions in midribs of symptomatic and asymptomatic grapevine leaves.
• Cross-cultural and multi-cultivar assessment of esca symptoms and vascular occlusions.
• Optical visualization of embolism propagation during leaf dehydration to assess hydraulic function.

Main Results:

• Leaves with esca symptoms showed significantly higher vascular occlusions (27% of vessels) compared to other stresses and controls (3% of vessels).
• Vascular occlusions did not correlate with the age of esca symptoms across the growing season.
• Occlusions caused hydraulic dysfunction, particularly in peripheral veins of esca-affected leaves.

Conclusions:

• Vascular occlusions are a key anatomical feature distinguishing esca leaf symptoms in grapevines.
• The findings highlight the unique physiological consequences of esca on leaf hydraulics.
• This research provides new insights into the role of xylem anatomy in plant stress responses and disease progression.