Intraspecific variation in functional strategies underlies susceptibility to a vascular disease in grapevine

Woody plant dieback involves complex interactions between pathogens, plant functional traits and environmental conditions. The role of intraspecific variation in functional strategies in shaping susceptibility to dieback remains unclear, despite its importance for understanding plant adaptation to changing environments. We used a common garden containing 46 Vitis vinifera (grapevine) cultivars to test the hypothesis that differences in grapevine susceptibility to esca, a complex vascular disease leading to dieback, result from intraspecific syndromes of leaf gas exchange, wood anatomical and metabolic traits, and microbiome. Cultivars with conservative water use strategies tended to be less susceptible to esca whereas xylem anatomy did not affect esca susceptibility. Across cultivars, symptomatic plants displayed decreases in leaf gas exchange, stem starch storage and theoretical hydraulic conductivity in response to esca. Symptomatic stems accumulated more secondary metabolites (mostly glycosylated flavonoids and terpenes) in highly susceptible than in weakly susceptible genotypes, whereas stem microbial communities were unaffected. This suggests that disease expression is linked to cultivar-specific metabolic responses. Intraspecific variation in physiological strategies contributes to differences in susceptibility to a complex vascular disease. Integrative studies unravelling plant-microorganism-environment interactions are crucial to improve our understanding of complex plant diseases.