Exploring the mechanisms underpinning grapevine susceptibility to esca in a range of Vitis vinifera L. cultivars

Abstract

Grapevine susceptibility to fungal diseases, including the vascular disease esca, is a major threat for wine productivity and vineyard perennity worldwide. The genetic diversity of grapevine cultivars could be a promising tool to mitigate disease impact in a sustainable manner. Our aim was (i) to study the genetic component of esca susceptibility, that has rarely been investigated, and (ii) to identify specific mechanisms and varietal traits underlying esca susceptibility amongst grapevine cultivars using a multi-trait approach of physiopathology and a common garden vineyard.

To describe the genetic component of esca susceptibility, we monitored for seven years esca incidence and severity in 46 cultivars randomly planted in the VitAdapt experimental vineyard (Bordeaux, France). We tested for phylogenetic autocorrelations between epidemiological metrics using cultivar SSR genotyping data. We then explored the relationships between esca incidence and ecophysiological traits monitored on the same plants: flowering date, δ13C in berry juice at maturity, stomatal conductance, N-tester at flowering, and pruning weight. On a subset of cultivars, we also studied the role in the varietal susceptibility of wood anatomical, functional and biochemical traits, microbiome and metabolome.

We first highlighted a broad and temporally consistent gradient of varietal susceptibility, with a mean annual incidence of 0 to 26 % of vines expressing esca foliar symptoms depending on the cultivar. A significant but weak phylogenetic signal was detected for the incidence of symptoms across this panel of cultivars. Then, we revealed a significant negative correlation between esca incidence and δ13C, suggesting that cultivars with high water use efficiency are less prone to express esca. We also identified a positive correlation between stomatal conductance and esca incidence. In addition, the least vigorous cultivars were among the least susceptible. To explore the underlying mechanisms esca susceptibility, we are analysing wood-related traits, as well as comparing the diversity, structure and composition of fungal and bacterial wood communities along the gradient of susceptibility.