Wood necrosis in esca-affected vines: types, relationships and possible links with foliar symptom expression

Abstract

Aims: Esca disease of grapevine is characterised by foliar symptoms associated with the development of various internal wood necroses. The aims of the present study are to determine the type and the quantity of necroses in the various woody compartments of vines, the relationships between them and the links between necroses and severity of foliar symptoms.

Methods and results: Symptomatic and asymptomatic vines cv Cabernet- Sauvignon were cross-sectioned to quantify the different types of internal necrosis in the scions (cordons, heads, and trunks) and rootstocks. Five necrosis « variables » were accounted for: central necrosis, sectorial necrosis, mixed necrosis, white rot, altered perimeter and in addition to the variable healing cone. In the scion, for all types of necrosis variables, a significant correlation between compartments was found. Vines with acute foliar form of esca had very advanced peripheral tissue degradations in the xylem and cambial zones. Chronic foliar expression of esca was associated with quantity of internal necroses higher than those obtained for asymptomatic vines. A logistic model indicated that white rot in the cordons was the best predictor for the chronic form of esca.

Conclusion: Necroses formed a continuum within the plant. The scion is like a single unit with a volume of necroses useful to determine the health status of vines.

Significance and impact of the study: A quantitative analysis of vine internal necroses would open up new possibilities for esca-epidemic approaches.