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Au laboratoire, les premiers prélèvements de ceps révèlent des différences en termes de surface de nécroses selon les modes de conduite

Une étude récente a permis d'établie l'impact du greffage sur l'expression des symptômes foliaires de la maladie de dépérissement

International audience; Esca is a Grapevine Trunk Disease (GTD) caused by a broad range of taxonomically unrelated fungal pathogens. These attack grapevine wood tissues inducing necroses even in the conductive vascular tissues, thus affecting the vine physiology and potentially leading to plant death. However, the influence of Esca on leaf and whole-plant water transport disruption remains poorly understood. In this paper, a detailed analysis of xylem-related physiological parameters in grapevines that expressed Esca-foliar symptoms was carried out. The experiments were conducted in a vineyard in the Bordeaux region (France) on cv. Cabernet-Sauvignon (Vitis vinifera L.) grapevines, which were monitored for Esca-foliar symptoms over a two-year period. Heat dissipation sap-flow sensors were installed during the summer on grapevines having expressed or not Esca-foliar symptoms. Leaf water potential, stomatal conductance and leaf transpiration were also measured. Physiological monitoring showed that sap flow density and whole-plant transpiration of Esca-infected grapevines decreased significantly a week before the first foliar symptoms appeared. When atmospheric water demand (Vapour Pressure Deficit, VPD) was the highest, both parameters tended to be about twice as low in symptomatic grapevines as in asymptomatic ones. Sap flow density data at the maximum transpiration-time, was systematically 29-30% lower in Esca-infected grapevines compared to control plants before or after the appearance of Esca-foliar symptoms. This trend was observed whatever the temperatures and VPD values measured. In Esca-diseased plants, larger amounts of necrotic wood, mainly white rot, were found in the trunk and cordon of symptomatic grapevines compared to healthy ones, suggesting necroses have an influence in reducing the whole-plant hydraulic capacity. This study reveals that the use of physiological monitoring methods, together with the visual monitoring of foliar symptoms, could prove useful in providing accurate measurements of Esca disease severity.

Grapevine Trunk Diseases (GTDs), particularly esca, are major concerns in Spain. This study characterized the fungal and bacterial communities in a 30-year-old ‘Cabernet Sauvignon’ vineyard in Catalonia, Spain. Six symptomatic vines expressing esca-foliar symptoms and six additional asymptomatic plants were surveyed. Non-necrotic and necrotic tissues were sampled from rootstocks, trunks and cordons of the selected vines. Fungal isolations and molecular techniques were used in combination to investigate the endophytic microflora and to characterize the fungal and bacterial diversity of the vines. Pathogenic fungi involved in GTDs were identified and the associations were assessed between all the isolated fungal taxa and the health status of vines, host partsand tissue types. Phaeomoniella chlamydospora and Diplodia seriata were found in non-necrotic tissues, whereas Fomitiporia mediterranea was mainly found in soft-rot tissues, and Neofusicoccum parvum and Eutypa cf. lata in hard necrotic tissues. Several Alternaria and Trichoderma species were isolated, mainly from non-necrotic tissues. Thesingle strand conformation polymorphism fingerprinting method showed differences in bacterial and fungal communities between the different types of tissue in healthy and diseased vines. However, no differences were detected in these microbial communities between non-necrotic tissues from asymptomatic and symptomatic vines. Two frequently-isolated species of Paraconiothyrium were tested for pathogenicity, but their pathogenic roles ongrapevines was unclear. info:eu-repo/semantics/publishedVersion

International audience; Esca is a widespread and damaging grapevine trunk disease in France. A survey was undertaken to identify relevant cultural factors that may influence symptom severity. Preliminary observations in the Aquitaine region confirmed the complex interactions among cultivar, vine training system, and climate, so the study was expanded to the national level to help account for esca in different wine growing regions. Twenty-five vineyard plots were examined. The plots were comparable by pairs, with the same cultivar (or cultivar with similar levels of susceptibility in a few cases), with the same age and similar soil and climatic environments, but with different training or pruning systems. Esca was the predominant trunk disease and prevalence was assessed by visible symptoms on leaves and on wood. Training systems with long arms (or cordons) were generally less affected by the disease than those with short or no arms. Pruning also played a major role, with a trend of less severe symptoms associated with less pruning. The study confirmed that foliar symptoms reveal the presence of the disease, but cannot be considered a reliable indicator of the disease impact in all situations. This study also confirmed: i) that vine training and pruning options may greatly influence the severity of esca, ii) that increasing the length of cordons may minimize the consequences of the wood necroses, and, iii) that simplifications of the woody vine structure (resulting from adoption of modern training and pruning options) may have favoured the development of esca.

Aim: The aim of the survey was to investigate if the grafting type influences the foliar expression of Esca during summer.Methods and Results: Observations were conducted on plots distributed in two French winegrowing regions (two different climatic regions) with two varieties (Cabernet-Sauvignon in the Bordeaux region and Mourvèdre in Provence). Three grafting types were compared: Omega graft, Whip and Tongue graft, and full cleft graft. For both varieties, we found a significant effect of the type of grafting on the foliar development of Esca symptoms. Full cleft grafted plots showed a significantly lower percentage of Esca foliar symptoms than the other two modalities, which were not significantly different from one another. Concerning Omega grafted plots, a significant difference in the rate of Esca foliar symptoms was highlighted compared to full cleft grafted plots, with a higher rate on Omega grafted plots, but these plots were also younger.Conclusions: The study established, for the first time, the difference between full cleft field grafted plots and Omega and Whip and Tongue grafted plots, revealing a higher incidence of Esca on the latter types of grafting.Significance and impact of the study: The spread of mechanical graft could be one of the factors explaining the increasing incidence of Esca in vineyard.

Vigne : pourquoi tailler moins ras aide à freiner l'esca

Dépérissement de la vigne. Confirmation du rôle de la conduite de la vigne (et de la taille) sur le développement de l'esca

International audience; Esca is a grapevine trunk disease (GTD) associated with different pathogenic fungi inhabiting the woody tissues. Bacteria can also be found in such tissues and they may interact with these fungal colonizers. Although such types of microbial interactions have been observed for wood diseases in many trees, this has never been studied for grapevine. In this study, the bacterial microflora of different vine status (esca-symptomatic and asymptomatic), different anatomical part (trunk and cordon) and different type of tissues (necrotic or not) have been studied. Based on Single Strand Conformation Polymorphism (SSCP) analyses, data showed that (i) specific complexes of bacterial microflora colonize the wood of both necrotic and non-necrotic tissues of esca-foliar symptomatic and asymptomatic vines, and also that (ii) depending on the anatomical part of the plant, cordon or trunk, differences could be observed between the bacterial communities. Such differences were also revealed through the community-level physiological profiling (CLPP) with Biolog EcoplatesTM. Two hundred seventeen bacterial strains were also isolated from plant samples and then assigned to bacterial species based on the 16S rRNA genes. Although Bacillus sp. and Pantoea agglomerans were the two most commonly isolated species from all kinds of tissues, various other taxa were also isolated. Inoculation of vine cuttings with 14 different bacterial species, and one GTD fungus, Neofusicoccum parvum, showed no impact of these bacteria on the size of the wood necroses caused by N. parvum. This study showed, therefore, that bacterial communities differ according to the anatomical part (trunk or cordon) and/or the type of tissue (necrotic or non-necrotic) of wood of grapevine plants showing external symptoms of esca disease. However, research into bacteria having a role in GTD development needs further studies.

International audience; La Yesca es hoy la enfermedad de la madera la más preocupante en Francia. Su progreso desde el final del siglo XX, incluso antes de la prohibición de arsenito de sodio, fue tal que algunos la han considerado como una “enfermedad emergente”. Después de recordar los principales datos del Observatorio Nacional para evaluar la situación de las principales “Enfermedades de la Madera de la Vid” durante la última década, este artículo sugiere varias hipótesis que pueden explicar la progresión de este síndrome. Se complementa con una sección sobre los síntomas y la dinámica de su aparición, que no había sido revisado durante casi un siglo. Los resultados de las observaciones finas y regulares en viñedo en Francia o en el extranjero, dan lugar a una redefinición de los síntomas de la yesca y conducen a nuevas preguntas. Este texto está inspirado en gran parte de un artículo publicado en 2012 y presentado en una conferencia del AFPP (Asociación Francesa para la Protección de las Plantas).

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International audience; Esca, a Grapevine Trunk Disease (GTD), is of major concern for viticulture worldwide. Our study compares the fungal communities that inhabit the wood tissues of vines that expressed or not foliar esca-symptoms. The trunk and rootstock tissues were apparently healthy, whether the 10 year-old plants were symptomatic or not. The only difference was in the cordon, which contained white rot, a typical form of esca, in 79% of symptomatic plants. Observations over a period of one year using a fingerprint method, Single Strand Conformation Polymorphism (SSCP), and the ITS-DNA sequencing of cultivable fungi, showed that shifts occurred in the fungal communities colonizing the healthy wood tissues. However, whatever the sampling time, spring, summer, autumn or winter, the fungi colonizing the healthy tissues of asymptomatic or symptomatic plants were not significantly different. Forty-eight genera were isolated, with species of Hypocreaceae and Botryosphaeriaceae being the most abundant species. Diverse fungal assemblages, made up of potentially plant-pathogenic and -protective fungi, colonized these non-necrotic tissues. Some fungi, possibly involved in GTD, inhabited the non-necrotic wood of young plants, but no increase in necrosis areas was observed over the one-year period.

L’esca est une maladie de dépérissement du bois de la vigne conduisant à la mort des ceps. Actuellement le vignoble mondial est atteint, et au niveau français, cette maladie ne cesse de progresser. Ainsi, 8% des ceps dans le Jura et 4,5% dans la région de Bordeaux manifestent des symptômes d’esca, selon les parcelles des chiffres beaucoup plus élevés sont obtenus, certains cépages sont aussi beaucoup plus sensibles que d’autres. Plusieurs champignons seraient impliqués dans l’esca mais leur rôle ainsi que la détermination de la microflore responsable de cette maladie est encore sujette à interrogation. Dans ce contexte, l’objectif de cette thèse a été de caractériser et de comparer les microflores fongiques et bactériennes colonisant le bois de ceps de vigne ayant exprimé ou non des symptômes foliaires d’esca. Dans un premier temps, nous avons prélevé des ceps (cultivar Cabernet Sauvignon) relativement jeunes (10 ans d’âge) car ils présentaient l’intérêt d’être peu dégradés au niveau du bois du tronc, les symptômes foliaires étant associés à la présence d’amadou (une nécrose typique de l’esca) uniquement dans les bras. Une grande diversité dans les communautés fongiques (674 OTUs) et bactériennes (222 OTUs) colonisant le bois a été observée. Cette diversité est plus importante dans le bois sain de la vigne que dans celui partiellement ou totalement nécrosé. Les techniques utilisées, i.e. isolement/séquençage de souches, empreinte moléculaire (Single Strand Conformation Polymorphism, SSCP) et pyroséquençage 454, ont montré que les communautés bactériennes ou fongiques étaient différentes dans les tissus dégradés comparés à ceux qui ne l’étaient pas. Des changements de microflores en fonction du temps (expérimentation durant 1 année) ont aussi été observés. D’une façon générale, les espèces de champignons impliquées dans l’esca sont déjà présentes dans le bois apparemment sain de ceps esca-foliaires symptomatiques mais aussi des asymptomatiques. Il n’a pas été possible de différencier ces 2 types de microflores au niveau du bois sain des plants, cette différentiation se faisant au niveau des nécroses, qui sont plus abondantes dans les ceps esca-symptomatiques. Pour la première fois nous avons montré que des communautés bactériennes spécifiques étaient associées à l’esca, leurs aptitudes trophiques étant différentes selon les tissus où elles étaient prélevées. Les espèces isolées suggèrent que certaines pourraient avoir un rôle dans la protection du végétal, d’autres dans la dégradation des structures du bois, e.g. de la lignine, préparant ainsi le terrain aux champignons dégradateurs des tissus ligneux, déjà présents à l’intérieur des ceps. Nous avons aussi étudiés des ceps plus âgés (cultivar Baco blanc), de 42 et 58 ans, qui avaient un rendement acceptable et n’avaient pas manifesté de symptômes d’esca ou eutypiose (une autre maladie du bois) l’année du prélèvement. Au niveau des tissus fonctionnels du bois, les communautés fongiques étaient caractéristiques de plants atteints par l’eutypiose (ceps de 42 ans) ou de l’esca (ceux de 58 ans). La non expression par les ceps de ces 2 maladies pourrait cependant être associée à la forte présence de champignons mycoparasites et protecteur du végétal, comme Trichoderma spp., dans ces tissus fonctionnels. Les interactions au sein des communautés fongiques créant un équilibre où le pathogène ne se développerait pas de façon extensive. Les caractéristiques du Baco blanc, un hybride, moins sensible à certaines maladies de la vigne, pourrait aussi expliquer ce résultat. Ainsi la présence d’une microflore bénéfique naturellement présente dans le bois des ceps associée à des plants ayant une tolérance à ces maladies pourrait ouvrir de nouvelles perspectives pour lutter l’esca, voire l’eutypiose, pour lesquelles aucun moyen de protection n’existe aujourd’hui., Esca is a Grapevine Trunk Disease (GTD) that induces a decline in grapevine vigour that generally leads up with the death of the plants. Nowadays, vineyards worldwide are attacked by esca and, in France this disease increases steadily. In the Jura, 8% of the grapevines are esca-foliar symptomatic and approximately 4.5% in the Bordeaux region. However, some vineyards are more severely attacked by esca, and certain cultivars are more susceptible than others. Although several pathogenic fungi are associated with esca, their individual roles and their interaction with other microorganisms for the esca have still to be determined. In this context, the objective of the present PhD study is to characterize and compare the bacterial and fungal microflora that colonize the wood tissues of esca-foliar symptomatic and asymptomatic grapevines. First, we sampled young (10 year-old) grapevines (Cabernet Sauvignon cultivar) because they had only few necroses in the trunk and white-rot (also called amadou) was only present in the cordons of symptomatic plants. Great diversity in the fungal (674 OTUs) and bacterial (222 OTUs) communities was observed. This diversity was higher in the apparently healthy wood than in the partially or totally necrotic wood tissues. The methods used isolation/sequencing of microbial strains, a molecular fingerprinting method (Single Strand Conformation Polymorphism, SSCP) and 454 pyrosequencing showed that the fungal and bacterial communities of the necrotic and healthy wood tissues were different. Changes in the microflora over time (over a one-year period) have been observed. Fungal species involved in esca are already present in the apparently healthy wood of esca-foliar symptomatic plants but also in the asymptomatic ones. It was not possible to differentiate these 2 microflora. Only microflora from the necroses differed from those of the healthy wood with these necroses being more developed in the esca-foliar symptomatic grapevines. For the first time, we were able to determine that specific bacterial communities are associated with esca. Depending on the wood tissues, different types of bacteria were isolated, with different trophic behaviour. Two roles could be assigned to the species isolated from the various wood tissues: (i) a positive role, due to the biocontrol potential that many species have; (ii) a negative one, by predisposing the wood of grapevines to fungal attacks. We also studied, old (42 and 58 year-old) grapevines of the cultivar, Baco blanc, that produced regular harvests. The plants had no expressed foliar symptoms of esca or eutypa dieback during the sampling year. Many plant pathogens colonized the functional wood tissues, but in 58 year-old plants they were associated with esca, and in 42 year-old plants, with eutypa dieback. The absence of GTDs expression could be linked to the numerous plant protectant mycoparasites, such as Trichoderma spp., that colonized the functional wood tissues. Interactions between species within the fungal communities may create a balance that is unfavourable to the development of the pathogens. The use of Baco blanc, a hybrid less susceptible to certain grapevine diseases could also explain this result. So, because no means of protection are currently available, the combination of beneficial microflora within the garpevine wood tissues with plants that are tolerant to esca, or even eutypa dieback, could be helpful to control those diseases.

National audience; L’esca est aujourd’hui la maladie du bois de la vigne la plus préoccupante en France. Selon les données obtenues par l'Observatoire National, sa progression a été constante de 2003 à 2008. Plusieurs hypothèses peuvent, individuellement ou conjointement, expliquer cette augmentation. Parmi elles, citons (i) l’interdiction de l’arsénite de soude en 2001, (ii) une décennie marquée par de fortes vagues de chaleur (2003, 2006) ou des sécheresses prolongées (2005, 2009, 2010), (iii) la qualité du matériel végétal et (iv) enfin les changements dans certaines pratiques viticoles. Au cours de la dernière décennie, un suivi basé sur l’apparition et le développement des symptômes foliaires a également été réalisé, principalement dans le Bordelais. Les résultats ont montré que les symptômes d’esca incluent des symptômes attribués par ailleurs au ‘black dead arm’. En Europe et sur le pourtour méditerranéen, les symptômes d’esca ont été très fréquemment associés à un désordre vasculaire très singulier: une lésion du bois externe, de couleur orangée, superficielle, longitudinale, plus ou moins large, située juste sous l’écorce et dans la continuité des symptômes foliaires. Ces observations soulèvent de nouvelles questions quant à l'étiologie de l'esca.

Test de la vraisemblance entre deux motifs de points

La vigne est sensible à de nombreuses maladies cryptogamiques qui vont altérer la qualité des raisins et des vins. Depuis plusieurs années, l’Esca est devenue un fléau pour la viticulture moderne, car elle est responsable de la mort des pieds de vigne lorsqu’elle se présente sous forme apoplectique. Sa forme chronique est liée à la présence d’un cortège de champignons pathogènes dans le tronc et les bras, qui vont provoquer le plus souvent des symptômes foliaires. L’altération de la photosynthèse que cela provoque, va avoir des conséquences sur la maturation du fruit. Cependant, peu de travaux de recherche ont été menés pour caractériser précisément l’impact de cette maladie sur le métabolisme et la composition chimique des baies de raisin. Notre étude avait pour but d’apprécier, grâce à une approche protéomique, les conséquences de cette maladie sur la qualité des raisins. Nos travaux ont permis de mettre en évidence que l’expression de symptômes foliaires d’Esca provoque une modification d’abondance des protéines liées aux mécanismes de défense et de stress oxydatif de la pellicule du raisin. Il est également observé un changement de capacité antioxydante par modulation des teneurs en peroxyde d’hydrogène, en glutathion ou en pyridoxine. Les concentrations en molécules d’intérêt œnologique comme les acides aminés, les amines biogènes ou les tannins sont également modifiées en présence de symptômes foliaires d’Esca., The vine is susceptible to many fungal diseases that will affect the quality of grapes and wines. For several years, Esca has become the bane of modern viticulture because it is responsible for the death of the vines when presented in the form apoplectic. Its chronic form is associated with the presence of a procession of pathogenic fungi in the trunk and arms that will most often cause leaf symptoms. The alteration of photosynthesis that this causes will affect fruit ripening. However, little research has been conducted to characterize precisely the impact of this disease on the metabolism and chemical composition of grape berries. Our study aimed to assess, using a proteomic approach the disease's impact on the quality of grapes and get specific markers. Our work allowed us to demonstrate that the expression of foliar symptoms of Esca causes a change in abundance of proteins related to defense mechanisms and oxidative stress in the grape skin. It is also observed a change in antioxidant capacity by modulating levels of hydrogen peroxide, glutathione or pyridoxine. The concentrations of molecules of oenological interest such as amino acids, biogenic amines or tannins are also modified in the presence of foliar symptoms of Esca.

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., Objectifs: La maladie de l’esca de la vigne est caractérisée par des symptômes foliaires associés au développement de différentes nécroses internes du bois. Les objectifs de cette étude sont de déterminer le taux et les types de nécroses dans les différents compartiments ligneux de la vigne, les relations entre eux et les liens existant entre les nécroses du bois et la sévérité des symptômes foliaires.Matériel et résultats: Des vignes, de cv. Cabernet-Sauvignon, symptomatiques et asymptomatiques sont sectionnées transversalement pour quantifier les différents types de nécrose du greffon (cordon, tête de souche, tronc) et du porte-greffe. Cinq variables « nécrose » sont définies: nécrose centrale, nécrose sectorielle, nécrose mixte, pourriture blanche, périmètre altéré, en plus de la variable cône de cicatrisation. Dans le greffon, il est montré une corrélation significative entre compartiments pour toutes les variables « nécrose ». Les vignes exprimant la forme sévère de l’esca présentent une forte dégradation des tissus ligneux périphériques comprenant la zone cambiale et la partie externe du xylème. La forme chronique de l’esca est associée à plusieurs types de variables « nécrose » de taille significativement plus importante que celles observées dans les vignes asymptomatiques. L’application d’un modèle logistique indique que la pourriture blanche est le meilleur prédicteur pour la forme chronique de l’esca. Conclusion: Les nécroses du bois forment un continuum à l’intérieur du greffon, celui-ci pouvant être considéré comme une unité caractérisée par un certain volume de nécrose, utile pour déterminer l’état sanitaire de la plante. Signification et impact de l'étude: Cette analyse quantitative des nécroses internes de la vigne pourrait ouvrir sur de nouvelles possibilités d’approches épidémiologiques de l’esca.

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