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International audience; Eutypa lata is the causal agent of eutypa dieback, one of the most destructive grapevine trunk disease that causes severe economic losses in vineyards worldwide. This fungus causes brown sectorial necrosis in wood which affect the vegetative growth. Despite intense research efforts made in the past years, no cure currently exists for this disease. Host responses to eutypa dieback are difficult to address because E. lata is a wood pathogen that causes foliar symptoms several years after infection. With the aim to classify the level of susceptibility of grapevine cultivars to the foliar symptoms caused by E. lata, artificial inoculations of Merlot, Cabernet Sauvignon, and Ugni Blanc were conducted over 3 years. Merlot was the most tolerant cultivar, whereas Ugni Blanc and Cabernet Sauvignon exhibited higher and differential levels of susceptibility. We took advantage of their contrasting phenotypes to explore their defense responses, including the activation of pathogenesis-related (PR) genes, oxylipin and phenylpropanoid pathways and the accumulation of stilbenes. These analyses were carried out using the millicell system that enables the molecular dialogue between E. lata mycelium and grapevine leaves to take place without physical contact. Merlot responded to E. lata by inducing the expression of a large number of defense-related genes. On the contrary, Ugni Blanc failed to activate such defense responses despite being able to perceive the fungus. To gain insight into the role of carbon partitioning in E. lata infected grapevine, we monitored the expression of plant genes involved in sugar transport and cleavage, and measured invertase activities. Our results evidence a coordinated up-regulation of VvHT5 and VvcwINV genes, and a stimulation of the cell wall invertase activity in leaves of Merlot elicited by E. lata, but not in Ugni Blanc. Altogether, this study indicates that the degree of cultivar susceptibility is associated with the activation of host defense responses, including extracellular sucrolytic machinery and hexose uptake during the grapevine/E. lata interaction. Given the role of these activities in governing carbon allocation through the plant, we postulate that the availability of sugar resources for either the host or the fungus is crucial for the outcome of the interaction.

Nowadays, grapevine wood decay diseases cause significant economic losses for the most sensitive varieties and represent a threat to the sustainability of the wine industry.This research focuses on the identification of molecular markers for sensitivity to Eutypa lata, responsible for Eutypiosis that could be used to diagnose the sensitivity of new grapevine clones or cultivars. Using an in vivo and in vitro infection assay, several potential markers genes for tolerance to Eutypiosis have been identified from a gene expression study on twelve different cultivars.Using an innovative in vitro infection system, the molecular dialogue (without physical contact) between Vitis vinfera foliars discs of and Eutypa lata was studied, leading to the identification of elicitors that could potentially play a role in the induction of defense responses in the cultivars. In addition, the expression of several sugar transport and invertase genes and their associated activities were demonstrated to be differentially regulated by the infection in tolerant and susceptible cultivars.Altogether, this research work led to the identification of several tolerance markers genes to Eutypiosis and to the development of a new, efficient and reliable in vitro infection system that could be used to diagnose new cultivar susceptibility. Furthermore, the results obtained demonstrated the importance of sugar transport and defense metabolism regulation during the infection of grapevine by Eutypa lata.; Les maladies du bois de la vigne, causées par des champignons nécrotrophes, ont un impact considérable sur l'économie viticole au niveau mondial. En effet, tous les cépages Vitis vinifera cultivés actuellement présentent une sensibilité plus ou moins forte à ces champignons.Dans le but d'établir un test rapide d'évaluation de la sensibilité de clones de vigne (nouvellement sélectionnés ou futures obtentions variétales) à Eutypa lata, le champignon responsable de l'Eutypiose, une recherche de marqueurs moléculaires de tolérance a été réalisée. Suite à l'infection in vivo et in vitro d'une douzaine de cépages de sensibilité différente par E. lata, plusieurs gènes candidats ont été identifiés comme marqueurs potentiels de la tolérance à la maladie à partir d'une étude transcriptomique.A l'aide d'un système innovant d'infection in vitro, le dialogue moléculaire sans contact physique entre des disques foliaires de V. vinifera et le mycélium d’E. lata a également été étudié chez les douze cépages. Cette étude a permis de mettre en évidence le rôle potentiel d'éliciteurs dans la mise en place des réponses de défenses. De plus, l'infection par E. lata régule différentiellement l'expression des gènes codant pour un transporteur d'hexoses et des invertases, ainsi que les activités invertasiques associées, chez les cépages de sensibilités variables.Les travaux de recherche présentées dans cette thèse ont ainsi permis l'identification des marqueurs de tolérance à l'Eutypiose et la mise au point d'un test d'infection in vitro efficace et fiable, permettant de diagnostiquer la sensibilité des futures créations variétales. De plus les résultats obtenus démontrent l'importance des éliciteurs dans la mise en place des défenses, de la régulation du transport et du métabolisme des sucres au cours de l'infection par E. lata.

Nowadays, grapevine wood decay diseases cause significant economic losses for the most sensitive varieties and represent a threat to the sustainability of the wine industry.This research focuses on the identification of molecular markers for sensitivity to Eutypa lata, responsible for Eutypiosis that could be used to diagnose the sensitivity of new grapevine clones or cultivars. Using an in vivo and in vitro infection assay, several potential markers genes for tolerance to Eutypiosis have been identified from a gene expression study on twelve different cultivars.Using an innovative in vitro infection system, the molecular dialogue (without physical contact) between Vitis vinfera foliars discs of and Eutypa lata was studied, leading to the identification of elicitors that could potentially play a role in the induction of defense responses in the cultivars. In addition, the expression of several sugar transport and invertase genes and their associated activities were demonstrated to be differentially regulated by the infection in tolerant and susceptible cultivars.Altogether, this research work led to the identification of several tolerance markers genes to Eutypiosis and to the development of a new, efficient and reliable in vitro infection system that could be used to diagnose new cultivar susceptibility. Furthermore, the results obtained demonstrated the importance of sugar transport and defense metabolism regulation during the infection of grapevine by Eutypa lata.; Les maladies du bois de la vigne, causées par des champignons nécrotrophes, ont un impact considérable sur l'économie viticole au niveau mondial. En effet, tous les cépages Vitis vinifera cultivés actuellement présentent une sensibilité plus ou moins forte à ces champignons.Dans le but d'établir un test rapide d'évaluation de la sensibilité de clones de vigne (nouvellement sélectionnés ou futures obtentions variétales) à Eutypa lata, le champignon responsable de l'Eutypiose, une recherche de marqueurs moléculaires de tolérance a été réalisée. Suite à l'infection in vivo et in vitro d'une douzaine de cépages de sensibilité différente par E. lata, plusieurs gènes candidats ont été identifiés comme marqueurs potentiels de la tolérance à la maladie à partir d'une étude transcriptomique.A l'aide d'un système innovant d'infection in vitro, le dialogue moléculaire sans contact physique entre des disques foliaires de V. vinifera et le mycélium d’E. lata a également été étudié chez les douze cépages. Cette étude a permis de mettre en évidence le rôle potentiel d'éliciteurs dans la mise en place des réponses de défenses. De plus, l'infection par E. lata régule différentiellement l'expression des gènes codant pour un transporteur d'hexoses et des invertases, ainsi que les activités invertasiques associées, chez les cépages de sensibilités variables.Les travaux de recherche présentées dans cette thèse ont ainsi permis l'identification des marqueurs de tolérance à l'Eutypiose et la mise au point d'un test d'infection in vitro efficace et fiable, permettant de diagnostiquer la sensibilité des futures créations variétales. De plus les résultats obtenus démontrent l'importance des éliciteurs dans la mise en place des défenses, de la régulation du transport et du métabolisme des sucres au cours de l'infection par E. lata.

UMR1334: Equipe AFEF ‘Architecture et Fonctionnement des Espèces fruitières’ article présenté lors du 2011 APS-IPPC Joint Meeting ; Honolulu - Hawaii (Etats-Unis) - (2011-08-06 - 2011-08-10) / Rencontres; International audience

International audience; Natural infestation and controlled inoculations of grapevine (mostly on the cultivar 'Cabernet Sauvignon'), were conducted in Bordeaux vineyards from 1998 to 2004 to evaluate the susceptibility to E. lata of spring wounds caused by the removal of either excess buds or excess suckers. Natural infestation was assessed across a range of sites to quantify and compare the relative risk of spring and winter pruning wounds to contamination by E. lata. Infestation caused by inoculation of wounds was examined in one site using either 100 (lower inoculum density) or 1000 (higher inoculum density) ascospores per wound. Wounds were allowed to incubate at the wound site for either two weeks or one year before isolations. For natural colonisation of wounds, a low level of infestation of spring wounds (average 2.1 %) was detected, less than those for winter pruning wounds (average 13 %). A similar trend was detected in trials involving inoculation of spring and winter pruning wounds despite infestation with identical levels of inoculum. No difference in recovery rates of E. lata was found between spring wounds caused by the removal of buds or suckers. A longer incubation period significantly increased the mean efficiency of recovery. We conclude that spring wounds may pose a significant risk to the colonisation of grapevine by the pathogen E. lata, albeit less than that of winter pruning wounds, suggesting a secondary role in the epidemiology of Eutypa dieback.

International audience; We tested differences in the aggressiveness of six fungal species, Phaeomoniella chlamydospora, Phaeoacremonium aleophilum, Fomitiporia mediterranea, Eutypa lata, Diplodia seriata and Neofusicoccum parvum, all of which are associated with esca, Eutypa dieback or 'black dead arm' (BDA) of grapevines in France. Ten isolates per species (nine isolates for P. aleophilum), originating in various regions of France, were tested on rooted cuttings of cv. Cabernet Sauvignon by inoculating the mycelium of the species on wounds made in the vine wood. The inoculated plants were incubated in an open greenhouse and the experiment was repeated twice. The isolates were divided into three groups depending on the severity of the infection. Infection severity was based on the extent of the external cankers and the internal lesions, measured 5 and 15 months after inoculation, as compared with the controls. The first group included all the P. chlamydospora and N. parvum isolates and two of the E. lata isolates. These isolates induced internal necrosis and external cankers developing from the point of inoculation. P. chlamydospora and N. parvum, produced large cankers and the longest internal lesions, and were the most virulent. The second group, comprising those E. lata isolates not in Group one and all isolates of D. seriata and of P. aleophilum, caused internal necrosis from which the vine afterwards totally healed. The third group included all the F. mediterranea isolates. These isolates caused the smallest lesions, generally not different from those in the controls, and developed a characteristic mycelium in the pith. No foliar symptoms were observed on any of the inoculated cuttings, except with the two E. lata isolates. Some seedlings displayed the typical foliar symptoms of Eutypa dieback. Different isolates within individual species exhibited significant differences (P < 0.05) in lesion development. This made it possible to select the most aggressive isolates for further study.

International audience; Eutypa dieback symptoms on grapevine have been reported in Rioja Alavesa since the nineteen eighties. However, attempts to find the perithecia of Eutypa lata in vineyards were not successful. Old vineyards in the Rioja Alavesa region were inspected for the presence of such perithecia. They were eventually detected in a 80-year-old Tempranillo vineyard in Laguardia. The morphology and size of the perithecia and the ascospores, as well as the colony features of the isolates on PDA were in agreement with those previously described for E. lata. The identification was confirmed by PCR using specific primers, as well as by sequence analysis of the rDNA ITS1/5.8S/ITS2 region. This is the first report of perithecia of E. later in Rioja Alavesa and will improve understanding of the disease cycle of Eutypa dieback of grapevine in this region.

International audience; The grapevine (Vitis vinifera) is susceptible to many pathogens such as Botrytis cinerea, Plasmopara viticola, Erysiphe necator, and Eutypa lata. Phytochemicals are used extensively in vineyards to reduce pathogen infections, but the appearance of pesticide-resistant pathogen strains and the need for environmental protection require the use of alternative strategies. The phytohormone ethylene is assumed to play a role in the development of disease resistance. In the present study, we have treated grapevine foliar cuttings (Cabernet Sauvignon) with ethylene-releasing ethephon. This resulted in an increase in the number of pathogenesis-related protein (CHIT4c, PIN, PGIP, and GLU) gene copies and in an enhancement of phytoalexin biosynthesis by inducing the PAL and STS genes that correlated with the accumulation of stilbenes (antimicrobial compounds). Moreover, ethephon treatment triggered the protection of grapevine detached leaves and grapevine foliar cuttings against Erysiphe necator, the causal agent of powdery mildew (64% and 70%, respectively). These studies emphasize the major role of ethylene in grapevine defense.

Among the numerous diseases affecting grapevine, eutypiose is very damaging. It is found in grape growing areas around the world and causes important economic losses. There is no known resistant cultivar and Cabernet sauvignon very frequent in Bordeaux vineyards is particularly sensitive to Eutypiosis. There is no treatment and no diagnostic tool for this disease. This work describes the transcriptomic study of the grapevine response (Vitis vinifera cv. Cabernet Sauvignon) to the vascular ascomycete fungus Eutypa lata, causing eutypiosis. Microarrays used allowed us to monitor simultaneously the expression of 15000 grapevine genes. Control and experimentally infected plants (with E. lata) were produced in vitro and in greenhouse. At the vineyard grapevines were selected based on historical notations symptoms of eutypiose between 2002 and 2006. The characterization of samples includes symptoms notation, re-isolation of the fungus in the lignified parts, and the formal identification of E. Lata mycelium by PCR. The characterization led to the identification of three types of plants: infected and showing symptoms (S+R+), infected showing no symptoms (S-R+) and healthy (S-R-). Leaf samples collected on these different kinds of plants were used for microarray analysis in each condition. The comparison between infected plants showing symptoms (S+R+) and healthy plants (S-R-) in vitro, in the greenhouse and in the vineyard allowed us to better describe the grapevine response to E. Lata infection. Many defence genes (21%) are over expressed in plants S+R+. A large number of differentially expressed genes (44%) are already identified as taking part in plant/fungus interactions, and other genes identified in this screening deserve attention. Comparison of transcriptomic data from greenhouse and vineyard plants infected without symptoms (S-R+) and healthy plants (S-R-), allowed us to identify 17 genes potentially useful for the development of an early and non destructive diagnosis tool. Finally, the combined analysis of microarray data obtained for the comparisons S+R+/S-R-,, S-R+/S-R- and S+R+/S-R+ in greenhouse and/or in vineyard led to the identification of genes that may be more specifically associated with the response to infection, or with the absence or presence of symptoms. The profiles of the candidate genes were controlled by RT-PCR (reverse transcription-polymerase chain reaction) with the same samples as those used for microarray studies and with leaf samples infected by other pathogens (U. necator, P. viticola, B. cinerea). The data are discussed in terms of alterations of cell metabolism., Parmi les nombreuses maladies affectant la Vigne, l’eutypiose est l’une des plus préoccupantes. Elle est présente dans les vignobles du monde entier et entraîne des pertes économiques significatives. Tous les cépages sont sensibles à l’eutypiose et le cépage Cabernet Sauvignon très fréquent dans le vignoble bordelais est particulièrement sensible. Il n’existe pas de méthode de lutte ou de technique de diagnostic non destructive efficace au vignoble. Enfin, la réponse de la vigne à l’infection par E. lata est encore mal connue. Ce travail concerne l’étude transcriptomique de la réponse de la vigne (Vitis vinifera cv. Cabernet sauvignon) au champignon vasculaire ascomycète Eutypa lata, responsable de l’eutypiose. Les puces à ADN utilisées permettent de suivre simultanément l’expression de 15000 gènes de Vigne. Des plantes saines ou infectées expérimentalement avec E. lata ont été produites in vitro et en serre. Au vignoble des ceps ont été sélectionnés d’après l’historique des notations des symptômes d’eutypiose entre 2002 et 2006. La caractérisation des échantillons comprend la notation des symptômes, le ré-isolement des champignons présent dans les parties lignifiés, et identification formelle du mycélium d’E.lata par PCR. Cette caractérisation a permis d’identifier trois types de plantes : infectées et présentant des symptômes (S+R+), infectées ne présentant pas de symptômes (S-R+) et saines (S-R-). L’expression génique a été étudiée à partir de feuilles prélevées sur ces différents types de plantes. La comparaison entre les plantes infectées présentant des symptômes (S+R+) et les plantes saines (S-R-) in vitro, en serre et au vignoble, a permis de décrire la réponse de la vigne à l’infection par E. lata. Les gènes de défense sur-exprimés chez les plantes S+R+ sont particulièrement nombreux (21%). Un grand nombre des gènes identifiés (44%) sont déjà connus pour intervenir au cours d’une interaction plante/champignon. Les analyses transcriptomiques comparées entre plantes infectées sans symptômes (S-R+) et plantes saines (S-R-) en serre et au vignoble ont permis d’identifier 17 gènes potentiellement utilisables pour le développement d’un outil de diagnostic précoce et non destructif. Enfin, l’analyse combinée des résultats obtenus pour les comparaisons S+R+/S-R-, S-R+/S-R- et S+R+/S-R+ en serre et/ou au vignoble a permis l’identification des gènes pouvant être plus spécifiquement associés à l’infection, à l’absence de symptômes ou à la présence de symptômes. Les profils d’expression de certains gènes candidats ont été confirmés par RTPCR (transcription inverse-récation de polymérisation en chaîne) avec les échantillons utilisés pour les microarrays et complétés avec l’analyse d’échantillons de feuilles de vignes infectées par d’autres pathogènes (U. necator, P. viticola, B. cinerea). Les résultats sont discutés en termes de réorientations du métabolisme cellulaire.

Correspondance: peros@supagro.inra.fr; International audience; We analysed symptoms, wood lesions and fungi associated with esca in mature organic vineyards in the Languedoc-Roussillon region. Most previous surveys concerning esca syndrome were conducted in conventionally managed vineyards in other regions. We first found that esca may be present at a very low level in vineyards that were not treated with sodium arsenite. Affected vines displayed three types of symptoms: leaves with interveinal necrosis, wilt of entire branches and these two symptoms in combination. During the 3-year survey, not all affected vines displayed symptoms every year and the same vine rarely displayed the same symptom or combination of symptoms in successive years. The incidence of esca appeared to be correlated with the percentage of vines that died during the survey but no correlation was found with either mortality before the survey or with the age of the vineyard. Observation of cross-sections of a total of 210 vines with esca symptoms and isolation of fungi from the wood lesions led to similar results to those obtained in conventionally managed vineyards. Four different lesions were identified: a white rot lesion, a brown lesion in a central position, a brown lesion in a sectorial position and a scattered black spotting in healthy wood. The most frequently observed fungal species were Fomitiporia mediterranea (Fom), Phaeomoniella chlamydospora, Phaeoacremonium aleophilum and Eutypa lata. The white rot lesion caused by Fom was generally accompanied by one or more other lesions in the same vine. Similarly, Fom was generally isolated with one or several other fungi. No relationship was detected between the expression of external symptoms and any specific lesion or fungus. Our study also showed that esca and Eutypa dieback are often superimposed in our region of sampling

Esca is a fungal syndrom found in the grapevine (Vitis vinifera) vascular system. During an initial phase, Phaeoacremonium aleophilum (PA), Phaeomoniella chlamydospora (PC) and, sometimes, Eutypa lata (EL) develop then allowing a latter infection from other fungal species. The recent banning of sodium arsenite left this syndrom out of control. Our work deal with PA, PC and EL properties, and also on the impact of natural molecules and commercial fungicides on the growth of these fungi. These pathogens exhibited different responses to these treatments and one of them (PA) was poorly or not affected. In parallel, we studied the ambimobility properties of salicylic acid (SA) and some of its halogenated derivatives. Our results showed that F 30 (an acidic derivative of fenpiclonil) was mobile into grape cuttings after a foliar treatment. F 30 was partially trapped in the wood and metabolized back to its parent molecule in the root system. 5-Chlorosalicylic acid (5-ClSA) which is known to be more active than SA on plant defense stimulation exhibited a similar phloem mobility. Therefore, F 30 and 5-ClSA have been selected for testing foliar treatments on infected grape cuttings. Such exploratoring research underline the complexity of the subject studied. Chemical treatments (fungicide) which generate several constraining elements, may be included in a wider strategy of disease control.; L'esca est un syndrome cryptogamique vasculaire de la vigne (Vitis vinifera). Une phase pionnière, sous la dépendance de Phaeoacremonium aleophilum (PA), Phaeomoniella chlamydospora (PC) et éventuellement de Eutypa lata (EL) permet la mise en place d'autres espèces. Depuis l'interdiction de l'arsénite de sodium, cette maladie n'est plus contrôlée. Nous avons étudié les propriétés de PA, PC et EL, en particulier l'impact sur leur croissance de fongicides commerciaux et de fongicides systémiques synthétisés au laboratoire, ainsi que de molécules naturelles. Ces pathogènes ne présentent pas la même sensibilité à ces molécules et l'un d'eux (PA) est peu affecté par divers traitements. En parallèle, nous avons étudié les propriétés d'ambimobilité de l'acide salicylique (AS) et de quelques-uns de ses dérivés halogénés. Nous avons montré que F 30, un dérivé acide du fenpiclonil, est mobile dans les boutures de vigne après application foliaire. Il est en partie retenu dans le bois et libère la molécule parent dans les racines. L'acide 5-chlorosalicylique (5-ClAS), connu pour être plus actif que AS pour stimuler les défenses naturelles, présente une mobilité voisine de celle de AS. Sur ces bases, F 30 et 5-ClAS ont été retenus pour des tests préliminaires de traitement par voie foliaire de boutures de vigne infectées. Cette recherche exploratoire souligne la complexité de la problématique, une lutte chimique (fongicide), génératrice de contraintes, devant s'intégrer dans une stratégie globale de contrôle.

International audience

International audience; A new acidic derivative of the fungicide fenpiclonil was synthesized containing a methyl group on the alpha-position of the carboxyl function of N-carboxymethyl-3-cyano-4-(2,3-dichlorophenyl)pyrrole. The phloem mobility of the resulting N-(1-carboxyethyl)-3-cyano-4-(2,3-dichlorophenyl)pyrrole was comparable with that of the former compound, but was higher at external pH 5.0. Unlike the derivatives previously synthesized, it was comparable with fenpiclonil in its fungicidal activity against the pathogenic fungus Eutypa lata.

Eutypa dieback, a devastating disease in grapevines, is caused by the fungal pathogen Eutypa lata, a wood-inhabiting fungus. E. lata acts by degrading wood tissues in the colonisation areas, and produces foliar symptoms. These striking symptoms have been attributed to the production of toxic metabolites by the pathogen, the most widely studied being eutypine. The aims of the study were to compare the effects of E. lata on xylem structure at the site of infection and in remote tissues. In healthy Vitis vinifera, the vessel-associated cells (VACs) in the trunk have a protective layer that covers the entire lignified wall and forms a transfer apparatus in pits located at the VAC / vessel interface. This apparatus occurs similarly in VACs in the basal part of canes but is less developed in the apical part. In the presence of E. lata, which is found only in the trunk and the cordons, the VACs initiated a program of secretory activity that led to the enlargement of the transfer apparatus, which is formed by tightly associated fibrils. This secretory activity was followed by VAC death. Furthermore, the hypertrophy of the transfer apparatus spread according to an acropetal gradient in the canes. Treatment with eutypine also induced the development of the transfer apparatus in VACs of basal and apical parts of canes excised from healthy vines. However, this apparatus was formed by loosely packed fibrils in VACs that were not completely damaged. Therefore, metabolites other than eutypine are expected to be involved in the VAC degeneration observed in infected vines.

The development of fungicides that are translocated in the phloem to control root and vascular diseases has long been needed. Attempts to derivatize fungicides to make them phloem mobile have generally had the discouraging consequence of decreasing or suppressing their biological activity.In this work, the first approach to this problem was similar to the successful strategy used in the development of acidic herbicides. The fungicide fenpiclonil was used as a model molecule because of the possibilities of adding a carboxyl group at various sites on the benzene or pyrrole rings. One of these derivatives, N-(1-carboxyethyl)-3-cyano-4-(2,3-dichlorophenyl)pyrrole exhibits a moderate phloem mobility and a fungicidal activity against a strain of Eutypa lata comparable to that of the parent compound.The second strategy was to synthesize phloem mobile propesticides by adding an amino acid to various xenobiotics or natural compounds involved in plant defense. These conjugates, with an a-amino acid function, are translocated by plasma membrane permeases and clearly move in the phloem. However, the enzymes which may release the parent compounds may be more specific than the carrier system.Finally, the capacity of Ricinus phloem to load salicylic acid (SA) was investigated for two motives: 1- SA is an important signal molecule involved in the acquired systemic resistance in plants, 2- in animal cells, SA is manipulated by a carrier system which also translocates drugs of larger size. SA strongly accumulates in the phloem and is ambimobile. In addition to the ion trap mechanism, some data rise the hypothesis of a pH dependent carrier system involved in SA phloem loading.; L'agriculture a besoin de fongicides ayant la propriété d'être transportés par le phloème pour contrôler des pathogènes vasculaires et racinaires. Jusqu'à présent, les tentatives de modulation structurale de fongicides pour les rendre phloème mobiles ont généralement eu comme conséquence une perte d'activité biologique.La première approche de notre travail reprend la stratégie utilisée avec succès pour le développement d'herbicides auxiniques. Nous avons choisi comme molécule modèle le fenpiclonil en raison de la possibilité d'ajouter un groupe acide carboxylique en divers sites de la molécule. L'un de ces dérivés, le N-(1-carboxyéthyl)-3-cyano-4-(2,3-dichlorophényl)pyrrole possède une mobilité phloémienne modérée et montre une activité fongicide contre une souche d'Eutypa lata comparable à celle du fenpiclonil.La deuxième stratégie a consisté à synthétiser des propesticides mobiles dans le phloème en greffant un acide aminé à divers xénobiontes ou à des composés naturels impliqués dans la défense des plantes. Ces conjugués avec une fonction a-aminoacide sont manipulés par des perméases de la membrane plasmique et sont nettement phloème mobiles. Toutefois, les enzymes qui peuvent libérer le composé initial peuvent être plus spécifiques que le système de transport.Enfin, la capacité du phloème de ricin à charger l'acide salicylique (AS) a été étudiée pour deux raisons : 1- l'AS est une molécule signal importante impliquée dans la résistance systémique acquise 2- dans les cellules animales, l'AS est manipulé par un système de transport qui manipule aussi des médicaments de taille importante. L'AS s'accumule fortement dans le phloème et est ambimobile. Quelques résultats conduisent à l'hypothèse de l'intervention d'un système de transporteurs dépendant du pH et contribuant au chargement phloémien de l'AS, outre le phénomène de piégeage d'acide.

National audience

International audience; Eutypine, 4-hydroxy-3-(3-methyl-3-butene-1-ynyl) benzaldehyde, is a toxin produced by Eutypa lata, the causal agent of Eutypa dieback in grapevine. The effect of the toxin on anthocyanin synthesis has been investigated in Vitis vinifera cv. Gamay cell cultures. At concentrations higher than 200 μmol/L, eutypine reduced anthocyanin accumulation in cells. The reduction in anthocyanin accumulation was proportional to the eutypine concentrations and HPLC analysis showed that eutypine affected the levels of all anthocyanins. The effect of eutypine application on the expression of five genes of the anthocyanin biosynthesis pathway, including chalcone synthase (CHS), flavonone-3-hydroxylase (F3H), dihydroflavonol 4-reductase (DFR), leucoanthocyanidin dioxygenase (LDOX), and UDP glucose-flavonoid 3-O-glucosyl transferase (UFGT) was determined. Expression of CHS, F3H, DFR and LDOX was not affected by the addition of eutypine to grapevine cell cultures. In contrast, expression of the UFGT gene was dramatically inhibited by the toxin. These results suggest that in grapevine cell cultures, eutypine strongly affects anthocyanin accumulation by inhibiting UFGT gene expression. The mechanism of action of eutypine is discussed.

International audience; Grapevine (Vittis vinifera L.) is susceptible to many pathogens, such as Botrytis cinerea, Plasmopara viticola, Uncinula necator, and Eutypa lata. Phytochemicals are used intensively in vineyards to limit pathogen infections, but the appearance of pesticide-resistant pathogen strains and a desire to protect the environment require that alternative strategies be found. In the present study, the, beta-1,3-glucan laminarin derived from the brown algae Laminaria digitata was shown both to be an efficient elicitor of defense responses in grapevine cells and plants and to effectively reduce B. cinerea and P viticola development on infected grapevine plants. Defense reactions elicited by laminarin in grapevine cells include calcium influx, alkalinization of the extracellular medium, an oxidative burst, activation of two mitogen-activated protein kinases, expression of 10 defense-related genes with, different kinetics and intensities, increases in chitinase and beta-1,3-glucanase activities, and the production of two phytoalexins (resveratrol and epsilon-viniferin). Several of these effects were checked and confirmed in whole plants. Laminarin did not induce cell death. When applied to grapevine plants, laminarin reduced infection by B. cinerea and R viticola by approximately 55 and 75%, respectively. Our data describing a large set of defense reactions in grapevine indicate that the activation of defense responses using elicitors could be a valuable strategy to protect plants against pathogens.

Resume L'eutypiose est une maladie de deperissement de la vigne due a un champignon parasite, Eutypa lata. C'est actuellement la plus grave des maladies de la vigne : elle est presente dans de nombreux vignobles a travers le monde, elle a un impact economique important et il n'existe pas de moyens de lutte curatifs. Dans cette mise au point, nous decrivons les symptomes et l'epidemiologie de la maladie, son impact economique et les mesures prophylactiques et preventives disponibles au vignoble. Nous presentons egalement les recherches qui ont permis d'apporter des connaissances fondamentales sur les interactions hote-parasite, et notamment, la mise en evidence et le role d'une substance toxique, l'hydroxy-4(methyl-3-butene-3-ynyl-1)-3 benzaldehyde, appelee eutypine, synthetisee par le champignon parasite et impliquee dans l'expression des symptomes de la maladie. La connaissance du mecanisme d'action de l'eutypine et de son devenir dans les cellules de vigne permet maintenant d'envisager une strategie pour developper des moyens de lutte visant a limiter l'expression des symptomes de cette maladie.