Grapevine vigour: a critical factor driving Trunk Disease expression

Abstract

Esca and Black Dead Arm (EBDA) are complex grapevine trunk diseases (GTD) that are major causes of mortality and production decline in French vineyards. Unravelling the different factors that determine symptom expression is crucial in mitigating the impact on growers. While cultivar, climate, age, and pruning system are known contributors, they do not fully explain the variability in EBDA occurrence. This study investigates the role of grapevine vigour as a determinant factor in EBDA expression. In 2022 and 2023, three vineyard networks were monitored, each consisting of approximately 30 vineyard plots of Grenache Noir, uniform in age. To minimize climate variation the selected vineyards were located within small geographical areas. We evaluated grapevine vigour and its primary drivers--water and nitrogen status, weed cover, production, and vegetation biomass--and correlated these factors with EBDA occurrence. Results show that current-year vigour is positively correlated with the EBDA incidence rate in all network*year scenarios. The relationship curve suggests that, while low to moderate vigour is consistently associated with reduced symptom expression, high vigour can be correlated with either high or low expression and implies the involvement of additional factors. In one instance, previous year water stress, of all tested variables, was most correlated with current year EBDA incidence, though vigour was also influential. In that case, EBDA expression seems to be maximal when water stress the year before is combined with a substantial current year spring vigour. While these results need to be confirmed over a longer period, in more regions and with other cultivars, they open new perspectives of applications for growers. They suggest a wider implication of grapevine physiology than just vigour.