Biology subjects

Gastou, P.

Publications and source records attributed to Gastou, P..

5 recordsLinked to original sources

bioRxiv2025

Investigating the intraspecific diversity of Vitis vinifera responses to esca with a physiopathology approach

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.

plant biology↗

bioRxiv2025

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 (i.e. secondary xylem) 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 Vitis vinifera L. cultivars grown in a common garden, and, at the cultivar level, we tested for correlations between (i) susceptibility to wood decay and esca expression (n = 16 cultivars) and (ii) wood biochemical traits, and healthy wood endophytic microbial communities (n = 23 cultivars). Unlike other types of necrosis, white-rot necrotic wood was significantly more abundant in plants that had expressed esca leaf symptoms in previous years, particularly in the most susceptible cultivars. These cultivars also contained significantly lower levels of constitutive wood extractives. However, glycosylated phenylpropanoids accumulated in the wood of esca-symptomatic plants, especially in highly susceptible cultivars. By contrast, esca expression and varietal susceptibility had only a marginal effect on the diversity, composition and putative functions of microbial communities in healthy wood. They did not influence either the relative abundance of Fomitiporia mediterranea, the putative causal agent of white-rot in grapevine. Esca susceptibility appears primarily linked to wood degradability and metabolic responses, rather than healthy wood's microbial communities, suggesting that the use of less susceptible varieties together with white-rot removal might attenuate grapevine decline.

plant biology↗

bioRxiv2025

Stress-dependent responses of grapevine wood and fungal pathogen activity under esca and drought

O_LIBiotic and abiotic stresses alter the physiology of perennial plants, with consequences for fungal endophytes and disease expression. In grapevine, one of the worlds most valuable crops, drought inhibits esca disease expression, but the underlying molecular interactions between plant and fungi are unknown. C_LIO_LIWe combined wood metatranscriptomics, metabolomics, and metabarcoding to investigate these interactions in 30-year-old grapevines and eight wood-pathogenic fungi under conditions of drought or esca leaf symptom expression. C_LIO_LIBoth esca and drought decreased grapevine transpiration, but with different transcriptomic and metabolic signatures. Similar pathways were also activated, including the phenylpropanoid and stilbenoid synthesis pathways. These stress responses could potentially confer cross-tolerance, and elicit different fungal molecular responses. The levels of putative fungal virulence factors increased significantly under both stresses. Under drought, only the relative abundance of Phaeomoniella chlamydospora and gene expression involved in anti-oxidative mechanisms, growth, and reproduction increased. Under esca expression conditions, only the relative abundance of Fomitiporia mediterranea and gene expression involved in wood degradation, competition, detoxification, and growth increased. C_LIO_LIThe grapevine defense mechanisms induced by drought coupled with a low transpiration rate and a low abundance and virulence of F. mediterranea may account for esca leaf symptom inhibition upon water deficit. C_LI

plant biology↗

bioRxiv2025

Differential impacts of drought and esca expression on Ascomycota fungi in the trunks and young organs of mature grapevines

Perennial plant decline is increasingly threatening the profitability and sustainability of agriculture and forestry worldwide. It results from intricate interactions between microbial communities, the plant host, and abiotic stressors. We investigated the effects of drought and esca disease on mature grapevine phytobiomes. Grapevines display no esca leaf symptoms during droughts, but the impacts of drought and esca expression on fungal communities and wood health in mature plants remain poorly understood. We studied 43 uprooted 30-year-old naturally infected vines in three experimental conditions: well-watered asymptomatic (Control) vines, vines with esca symptoms (Esca), and vines subjected to water deficit (WD) over two consecutive summers. We profiled trunk, cane, stem and petiole Ascomycota communities by DNA metabarcoding with primers specifically designed for grapevine trunk-associated Ascomycota, and quantified wood necrosis. The Ascomycota communities of trunks and younger organs clearly differed, and drought and esca had different impacts on the Ascomycota communities of perennial and young organs. In the trunk, drought significantly decreased fungal diversity in healthy wood and increased the abundance of wood pathogens (e.g. Phaeomoniella chlamydospora, Botryosphaeria dothidea). In young organs, esca expression decreased the species richness and diversity of the Ascomycota community to a greater extent than drought. We also found that the relative proportion of healthy wood was smaller in plants with esca symptoms than in control plants. Thus, drought increased Ascomycota pathogen abundance in the trunk but did not increase wood degradation and esca expression, highlighting the need to investigate the molecular basis of plant-microbiome interactions under multi-stress conditions.

plant biology↗

bioRxiv2024

Large gradient of susceptibility to esca disease revealed by long-term monitoring of 46 grapevine cultivars in a common garden vineyard

Grapevine (Vitis vinifera L.) is prone to many fungal diseases, including esca, a severe vascular disease threatening the wine sector and for which there is no cost-effective cure. Susceptibility to esca varies between cultivars in different infection conditions. It may therefore be possible to use the genetic diversity of grapevine cultivars to mitigate disease impact. However, the genetic component of esca susceptibility has rarely been investigated in the vineyard, and the specific mechanisms and varietal traits underlying esca susceptibility remain unknown. In this study, we monitored the incidence and severity of esca foliar symptoms and plant dieback (apoplexy and mortality) at plant level for seven years, on 46 cultivars planted in an experimental common garden, to separate the genetic component of esca susceptibility from the effects of environment and cropping practices. We observed a broad gradient of varietal susceptibility, with a mean incidence of 0 to 26% of vines expressing esca foliar symptoms depending on the variety. This gradient remained similar across years and, unlike the severity of foliar symptoms, the incidence of grapevine dieback was significantly correlated with that of foliar symptoms. We detected a significant but weak and very localised phylogenetic signal for the incidence of esca foliar symptoms in this panel of cultivars. We then explored the relationships between epidemiological metrics and ecophysiological and phenological traits phenotyped on the same plot. Esca disease incidence was negatively correlated with {delta}13C across cultivars, suggesting that varieties with higher water use efficiency are less prone to the expression of esca symptoms on leaves. Moreover, the least vigorous cultivars were among the least susceptible, although this relationship was not significant. By contrast, neither phenological stages nor nitrogen status were significantly predictive of cultivar susceptibility to the disease. Together, these results provide new insight into the potential of genetic resources for use in the sustainable management of grapevine trunk diseases and open up new perspectives for studying the pathological and physiological determinants of their incidence.

plant biology↗