Wood composition, rather than microbial communities, underpins varietal differences in wood degradation and esca foliar symptom expression in grapevine

Deciphering the interplay between microbial communities and host defence mechanisms is key to understanding plant health. In perennial plants, the balance between endophytes and wood defence responses governs wood degradation and vascular disease expression. Esca is a complex vascular disease contributing to grapevine decline, with an incidence variable across cultivars but the mechanisms underlying its expression and varietal susceptibility remain unclear. We assessed relationships between internal wood degradation and esca foliar symptoms in 23 Vitis vinifera L. cultivars grown in a common garden, to determine how healthy wood biochemical traits, endophytic microbial communities, and fungal pathogen traits contribute to susceptibility. Unlike other types of necrosis, white-rot necrosis was significantly more abundant in previously symptomatic plants, especially in the most susceptible cultivars. These cultivars had slightly higher hemicellulose levels and significantly fewer extractives in healthy wood. Glycosylated phenylpropanoids accumulated in the wood of esca-symptomatic plants, especially for susceptible cultivars. By contrast, neither esca expression nor cultivar susceptibility affected the diversity, composition or function of microbial communities in healthy wood. Esca susceptibility appears primarily linked to wood degradability and metabolic responses rather than microbial communities, suggesting that the use of weakly susceptible varieties together with white-rot removal might attenuate grapevine decline.