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International audience; The most sustainable management of resistant varieties involves understanding which defence mechanisms the plant uses according to its resistance genes and stage of development and how effective these mechanisms are. Three grapevine varieties were compared for their susceptibility versus resistance to powdery mildew: Vitis vinifera 'Cabernet Sauvignon' (CS) and two hybrids, 'Artaban' and 'Prior'. Four different leaf ages were collected from 2-year-old grafted grapevines planted in pot or in vineyard, and several variables were assessed for each leaf: (a) morphological and physiological indicators, (b) pathogenicity traits: spore germination, infection ef?ciency, mycelial growth and sporulation, and (c) gene expression using a high-throughput quantitative reverse transcription PCR method to inform about plant defence status and functioning of primary metabolism. A significant decrease in germination and sporulation with increasing leaf age were observed for the three varieties: Prior showed a susceptibility similar to that of CS, whereas Artaban was fully resistant with no sporulation. Genes highlighted as markers of the variety were involved in defence (VvPR3, VvPR4 overexpressed in Artaban, VvPR4bis, VvAlli2 in Prior) or in primary metabolism (repression of VvCitS in Artaban, VvCHI in Prior, overexpression of VvCAD2, VvGST3 in Prior). After inoculation, more defence genes, especially PR proteins, were overexpressed in the oldest leaves as potential components of ontogenic resistance. PR proteins accounted for 25% of total disease variation. Phenylpropanoid and ethylene pathways were leaf age-dependent. The statistical method used highlighted the contributions of the genotypic expression involved in genetic (cultivar) and ontogenic (leaf age) resistances and of the metabolic pathways to the disease.

Background The primary strategy to control powdery mildew in Chilean vineyards involves periodic fungicide spraying, which may lead to many environmental and human health risks. This study aimed to implement and evaluate the effectiveness and economic feasibility of a novel decision support strategy (DSS) to limit the number of treatments against this pathogen. An experiment was conducted between the 2010 and 2013 seasons in two irrigated vine fields, one containing a cultivar of Cabernet Sauvignon (CS) and the other a cultivar of Chardonnay (CH). Results The results showed that the DSS effectively controlled powdery mildew in CS and CH vine fields, as evidenced by a disease severity lower than 3%, which was lower than that observed in untreated vines (approximately 10 and 40% for CS and CH respectively). The DS strategy required the application of only 2-3 fungicide treatments per season in key vine phenological stages, and the cost fluctuated between $US 322 and 415 ha-1 , which was 40-60% cheaper than the traditional strategy employed by vine growers. Conclusion The decision support strategy evaluated in this trial allows a good control of powdery mildew for various types of epidemic with an early and late initiation. © 2017 Society of Chemical Industry.

How and when the pathogen cycle is disrupted during plant development is crucial for harnessing ontogenic resistance in sustainable agriculture. Ontogenic resistance against powdery mildew (Erysiphe necator) was quantified on Vitis vinifera. Shoots were sampled in the vineyard at several dates during seasonal growth and processed in the laboratory under controlled conditions. Experiments were conducted on two susceptible Vitis vinifera Cabernet Sauvignon and Merlot. The process of leaf ontogenic resistance was investigated by measuring three quantitative traits of pathogenicity: the infection efficiency, sporulation and mycelium growth. Morphological and physiological plant indicators were used to identify leaf changes that resulted in ontogenic resistance and to predict pathogen variations that were linked to pathogenicity traits. The process of ontogenic resistance was established early in correspondence with the physiological transition of the leaf from sink to source status and was characterised by its increase in sugar content. The three traits of pathogenicity that we measured were affected, and their variation was strongly correlated with leaf age. Using leaf age, we were able to accurately predict the susceptibility of the leaf: a leaf aged, on average, 13.3 days had a very high probability (0.8) of being susceptible, while this probability decreased to 0.5 one week later. Sporulation was more closely correlated with variations in sugar and the infection efficiency in leaf water. The results for both cultivars were consistent. Ontogenic resistance on grapevine leaves is thus interpreted to be a strong, immutable physiological process that Erysiphe necator is able to circumvent by restricting its development to sink tissue. Future research should explore how this native plant resistance can be incorporated into grape management strategies to better control powdery mildew (PM) epidemics with reduced amounts of fungicides.

National audience; La région Nouvelle-Aquitaine est l’une des plus grandes régions agricoles en Europe. Elle abrite une agriculture très diversifiée avec de nombreuses productions emblématiques comme le vin et le cognac, le maïs et le blé ou encore les fruits, et un élevage de haute qualité. Le secteur agricole sera d’autant plus affecté par le changement climatique que la hausse des températures pourrait être plus importante dans le quart Sud Ouest de la France. Les ressources de base, à savoir le sol et l’eau, tout comme l’élevage et les cultures sont sensibles aux changements climatiques et sociétaux ; la recrudescence des risques sanitaires en est un contrecoup. En fonction des cultures et des productions animales considérées, les répercussions seront variées, quelquefois positives mais le plus souvent négatives, avec des constantes sur la précocité, le rendement, et la qualité des produits récoltés. Pour chacune de ces productions, il existe des adaptations possibles qui doivent être combinées pour maintenir le potentiel productif et qualitatif, tout en minimisant l’impact environnemental. Les mesures contribuant à la fois à réduire l’émission de gaz à effet de serre par le secteur agricole et à s’adapter aux changements irrémédiables du climat devront être favorisées. L’irrigation devra être questionnée et gérée en adéquation avec l’ensemble des usages de l’eau. Pour répondre aux enjeux auxquels doit faire face l’agriculture en Nouvelle-Aquitaine, il sera important de mobiliser tous les acteurs du monde agricole, des filières et des territoires, et de la recherche.

Aim: This paper aimed to address the relationship between grapevine disease, pest occurrences and climate. The extremely large extension of viticulture worldwide offers the possibility to evaluate the impacts of climate variability on many aspects of the grape growing system. For this, we initiated a global survey to retrieve the most important diseases and pests in many grape growing regions worldwide and to identify the risk of exposure to pests and diseases of viticulture as a function of climate.Methods and results: Based on the answer of respondent about the main reported diseases/pests in their region, a severity index was calculated. Each region was geolocalised and data were compared to the WorldClim gridded climate database to document the range of climate conditions (growing season temperature and rainfall) associated to the main diseases/pests. The potential climatic-induced changes of grapevine disease and pest geography by 2050 are assessed using agro-climate projections from the ARPEGE CNRM model, using the RCP 4.5 scenario. The preliminary results allow to determine the distribution of diseases as function of agroclimatic indicators.Conclusion: While the distribution of diseases differs according to the region of the world, the current analysis suggests that mildews remain the major phytosanitary threat in most of the regions. Powdery mildew, trunk diseases and viruses were reported in extremely diverse climatic conditions, including intermediate and wet regions. Significance and impact of the study: This paper present an original methodology to address the relationship between grapevine disease and pest occurrences and climate. Such documentation is scarce in the current literature. Further analysis is currently being performed, including additional survey answers, climate indices and supplementary data collected (spatial extension, frequency of treatments…) to better depict the challenges of grapevine phytosanitary management in a changing climate.

UMR AGAP - équipe AFEF - Architecture et fonctionnement des espèces fruitières; International audience; Ideotypes are a popular concept for plant breeders, who designate as such the ideal combinations of traits in a particular genotype to reach a pre-set production objective within a given socio-economic context. The historical, ‘genetic’ view of ideotypes has been more recently extended to cover the design of plant genotypes for specific cropping systems (the ‘agronomic’ view), or even the ideal combination of parameters, identified from formal or simulation modeling, to a specific agronomic problem (the ‘modelling’ view). These different forms of ideotypes in turn lead to different strategies for breeding plants. This paper will briefly describe, analyse and discuss some applications of these ideotype views, using the specific case of architectural traits of plant and crop canopies to limit the epidemic development of pests and diseases in crops. It is not intended to be an exhaustive and objective review of the existing literature on plant ideotypes, but rather to express as an ‘opinion’ paper the views discussed and elaborated among participants to the EpiArch network.

This study was designed to assess the reliability of grapevine leaf bioassays for predicting disease resistance on fruit in the field. The efficacy of various grapevine quantitative trait loci (QTLs) for conferring resistance to downy and powdery mildew was evaluated in bioassays and in a 2-year field experiment for downy mildew. The resistance genes studied were inherited from Muscadinia rotundifolia (Rpv1 and Run1 )a nd from AmericanVitis species through cv. Regent (QTLRgP and QTLRgD). In bioassays, genotypes carrying Run1 blocked powdery mildew development at early stages. Genotypes combining Run1 with QTLRgP displayed no greater level of resistance. For downy mildew, genotypes carrying Rpv1 and ⁄or QTLRgD were more resistant than the susceptible cv. Merlot, and showed a high level of leaf resistance in the field (

BACKGROUND: Limiting the use of fungicides is due to become an important issue in managing Erysiphe necator (Schwein) Burrillinfectionsinvineyards.Theauthorsdeterminedhow threefungicides currentlyusedby vinegrowers could be managed to control the early stages of an E.necator-induced epidemic. RESULTS: Leaf-disc bioassays and field experiments suggested that the protectant quinoxyfen induced minor disruption in E. necator development, but compounds with protectant and curative properties (tebuconazole and trifloxystrobin) caused significant, although different, disruption during E. necator-induced epidemics. Bioassays showed that each of the antifungals were most effective at different stages of fungal development, tebuconazole before sporulation and trifloxystrobin after sporulation of the colonies. Results from the bioassay also highlighted likely occurrences in the field, where several stages of fungal development are encountered simultaneously. CONCLUSION: The present findings were complementary: leaf-disc tests showed when the fungicides were most effective at inhibiting E. necator infection cycles; the field trial provided results in terms of incidence and severity of disease on bunches withoutreferencetothepathogeniccycledevelopment.Aprotectionstrategycombiningthedifferenttypesoffungicideunder study is suggested. c � 2010 Society of Chemical Industry Supportinginformationmaybefoundintheonlineversionofthisarticle.

Calonnec, A., Cartolaro, P., and Chadœuf, J. 2009. Highlighting features of spatiotemporal spread of powdery mildew epidemics in the vineyard using statistical modeling on field experimental data. Phytopathology 99:411-422. A greater understanding of the development of powdery mildew epidemics on vines would improve disease management by making assessments of the risk of invasion more accurate. We characterized the spatiotemporal spread of epidemics in the vineyard, quantified their variability, and identified the factors responsible for it. We described changes in the probability of infection of a leaf in a plot over time and as a function of distance from a source of disease. Logistic models were fitted to field data from artificially inoculated plots. The velocity of spread decreased along the row and increased in the direction of the prevailing winds. The rate of progression over time was plot dependent, and the velocity was dependent on the vigor of the vine (0.1 to 0.27 m day–1 in areas of moderate vigor and 1.1 m day –1 in areas of high vigor). When applied to a larger plot with natural primary foci, the spatiotemporal logistic model showed that the velocity and the slope of the gradient in space depended on the foci; however, the velocity remained in the same range. During the period of highest susceptibility for grape, the probability of a leaf becoming infected increased from 2.5 to 13%. Our logistic model was able to predict changes in disease over time of its extension within the plot; however, the crop heterogeneity prevented prediction of variability of disease at the vine scale.

The dominant strategy followed by vine-growers in Chile to control powdery mildew (Erysiphe necator) involves schedule phytosanitary applications resulting between 9 to 18 fungicide sprays depending on the grape cultivar and the geographical area, mainly with sulphur applications. This large application of chemicals generates many environmental and human health risks To solve this, the present study aimed at evaluating the effectiveness of a Phytosanitary Decision Rule (PDR) proposed by French pathologists to rationalize fungicide applications against powdery mildew in grapevine. The PDR was evaluating in two irrigated vine fields, one of cultivar Cabernet sauvignon (CS, 1.56 ha) and another of Chardonnay (CH, 1.66 ha), in the Mediterranean climatic conditions of Talca Region, Chile. The experiment was carried out between 2009 and 2013. For the two experimental fields, two strategies to control powdery mildew were distributed in a randomized block design with four replicates: i) “Optimized traditional management” (OPT), which consisted in periodic applications (mainly sulphur), but with no more than nine treatments per season, ii) Application of a PDR based on field observations but with no more than four treatments per season. Untreated vines were left in each block to assess disease pressure at each studied season. Finally, a survey was conducted to know the practices of crop protection of traditional vine-growers (TVG) in the area, who carry out a “zero risk” strategy without limiting the number of phytosanitary applications. At veraison stage, clusters were observed to assess disease severity. The results show that powdery mildew control based on a PDR was as effective as schedule applications used by the OPT at experimental station for both vine fields. In the OPT and PDR treatments disease severity was lower than 5 %, which was considered as a threshold value for avoid in gloss of wine quality. For both cultivars disease severity was lower than that observed in untreated vines (close to 10% and 40 % for CS and CH, respectively). In the OPT treatment 7 to 9 applications per season independent of cultivar were made, whereas in the PDR treatment only 2-4 application were carried out. The differences are even greater when comparing the PDR with the TVG strategy in which, independent of the season and the cultivar, performed an average of 14 fungicide applications. Finally in the OPT and PDR treatments the cost per season was similar and fluctuated between US $ 322 and 415 per hectare independent of the cultivar. This value is 60% lower than the cost of the traditional "zero risk" strategy of vine-growers.; La principale stratégie de contrôle de l'oïdium (Erysiphe necator) suivie par les viticulteurs chiliens se fait par applications phytosanitaires périodiques. Selon le cépage et la zone géographique, cela se traduit par 9 à18 applications de fongicides par saison, principalement sous forme de soufre. Cette utilisation importante de produits chimiques entraîne d’importants risques pour la santé humaine et l'environnement. Pour résoudre ce problème, cette étude vise à évaluer l'efficacité d'une règle de décision phytosanitaire(PDR) proposé par des pathologistes français. Cette PDR a pour objectif de rationaliser les applications de fongicides contre l'oïdium de la vigne. La PDR a été évalué sur deux parcelles viticoles irriguées, une avec le cépage Cabernet-Sauvignon (CS, 1,56 ha) et l’autre avec Chardonnay (CH, 1,66 ha), dans les conditions climatiques méditerranéennes de la région de Talca au Chili. L'étude a été réalisée de 2009 à 2013. Pour les deux parcelles expérimentales, deux stratégies de lutte contre l'oïdium ont été mises en oeuvre en blocs aléatoires avec quatre répétitions: i) “Gestion traditionnelle optimisée" (OPT), qui consiste en des applications périodiques(principalement soufre), mais avec un maximum de neuf traitements par saison, ii) Application d'une PDR basée sur des observations de terrain, avec un maximum de quatre traitements par saison. Des plantes non traitées ont été laissées au sein de chaque bloc pour évaluer la pression de la maladie à chaque saison étudiée. Enfin, une enquête a été menée pour connaître les pratiques de protections traditionnelles des vignerons dans la région, qui effectuent une stratégie de “risque zéro” sans limite du nombre de traitements fongicides. Au stade véraison, les grappes ont été observées pour évaluer la sévérité de la maladie. Les résultats montrent que pour les deux parcelles de l’étude, le contrôle de l'oïdium avec la PDR est aussi efficace que la OPT.. Dans les traitements OPT et PDR la sévérité de la maladie est inférieure à 5%, ce qui est considéré comme une valeur seuil au-dessus de laquelle la qualité du vin est altérée. Pour les deux cépages la sévérité de la maladie sur les vignes traitées a été inférieure à celle observée sur les vignes non traitées (près de 10% et 40% respectivement pour CS et CH). Indépendamment du cépage, 7-9 applications par saison ont été effectuées pour le traitement OPT, alors que seulement 2-4 applications ont été réalisées pour le traitement PDR. Les différences sont encore plus importantes lorsque l'on compare la PDR à la stratégie de protections “risque zéro” menées par les viticulteurs de la région pour laquelle, indépendamment de la saison et le cépage, 14 applications par saison ont été effectuées en moyenne. Enfin pour les traitements OPT et PDR le coût par saison était similaire et a fluctué entre US $ 322 et 415 par hectare, valeur qui est 60% inférieure au coût de la stratégie “risque zéro” de viticulteurs.

We investigate the structure of travelling waves for a model of a fungal disease propa- gating over a vineyard. This model is based on a set of ODEs of the SIR-type coupled with two reaction-diffusion equations describing the dispersal of the spores produced by the fungus inside and over the vineyard. An estimate of the biological parameters in the model suggests to use a singular perturbation analysis. It allows us to compute the speed and the profile of the travelling waves. The analytical results are compared with numerical simulations.

Thebaud, G., Peyrard, N., Dallot, S., Calonnec, A., and Labonne, G. 2005. Investigating disease spread between two assessment dates with permutation tests on a lattice. Phytopathology 95:1453-1461. Mapping and analyzing the disease status of individual plants within a study area at successive dates can give insight into the processes involved in the spread of a disease. We propose a permutation method to analyze such spatiotemporal maps of binary data (healthy or diseased plants) in regularly spaced plantings. It requires little prior information on the causes of disease spread and handles missing plants and censored data. A Monte Carlo test is used to assess whether the location of newly diseased plants is independent of the location of previously diseased plants. The test takes account of the significant spatial structures at each date in order to separate nonrandomness caused by the structure at one date from nonrandomness caused by the dependence between newly diseased plants and previously diseased plants. If there is a nonrandom structure at both dates, independent patterns are simulated by randomly shifting the entire pattern observed at the second date. Otherwise, independent patterns are simulated by randomly reallocating the positions of one group of diseased plants. Simulated and observed patterns of disease are then compared through distance-based statistics. The performance of the method and its robustness are evaluated by its ability to accurately identify simulated independent and dependent bivariate point patterns. Additionally, two realworld spatiotemporal maps with contrasting disease progress illustrate how the tests can provide valuable clues about the processes of disease spread. This method can supplement biological investigations and be used as an exploratory step before developing a specific mechanistic model. Additional keywords: censoring, distance class, European stone fruit yellows, nonparametric, Plum pox virus, toroidal shift.

Genetic analysis of resistance of wheat seedlings to two races of Puccinia striiformis was conducted on F1, F2 and F3 generations from crosses Carstens V (CV) × Lee, Spaldings Prolific (SPA) × Lee and CV × SPA. F2 generations from crosses of CV and SPA with Strubes Dickkopf (SD) were also studied. The plants were classified into six resistance classes and analysed by factorial correspondence analysis and nonhierarchical classification. The two P. striiformis isolates tested were a French isolate of race 43E138 and a Lebanese isolate of race 2E16, selected for the differences in their virulence spectra for the common differential cultivars Strubes Dickkopf and Nord Desprez. Resistance of CV and SPA was recessive and dominant to races 43E138 and 2E16, respectively. CV possessed three or four resistance genes, one of them being expressed with both races. Two genes of CV had a cumulative effect for resistance to 43E138 and two or three gave dominant resistance to 2E16. SPA had three resistance genes, all of which gave resistance to 2E16 and two of which also gave resistance to 43E138. SPA had one gene in common with CV for resistance to both races. Furthermore, the gene for resistance to race 2E16 in CV and SPA was allelic with a gene in SD, and was probably Yr25.

International audience; A PDEs–ODEs model was developed to describe the spread of an airborne fungal pathogen on grapevine. The model was able to retrieve the main characteristics of the system: (1) a host growing during the whole season with time evolution in susceptibility, (2) a crop highly structured in rows with potential heterogeneities of plant growth and susceptibility within and between plots. These characteristics are modified by cultural management. Simulations were performed to test the effect of crop spatial heterogeneities, within and between plots, on the disease spread. Heterogeneities considered were the plant growth (vigour, earliness), susceptibility (susceptible vs resistant, treated vs untreated) and the spatial arrangements (patches vs rows). The main effect on disease reduction was obtained by arrangement in rows of susceptible and fully resistant plants.

International audience; To reduce the use of pesticides, innovative studies have been developed to introduce the plant as the centre of the crop protection system. The aim of this paper is to explain how architectural traits of plants and canopies induce a more or less severe epidemic and how they may be modified in order to reduce disease development. In particular, it focuses on three key questions: i) which processes linked to epidemics can be influenced by architecture ii) how can architecture be characterized relative to these modes of action, and iii) how can these effects be explored and exploited? The roles of plant/canopy architecture on inoculum interception, on epidemic development via the microclimate and on tissue receptivity are discussed. In addition, the concepts of disease avoidance, canopy porosity and an ideotype unfavourable for disease development are described. This paper shows that many advances have already been made, but progress is still required in four main fields: microclimatology, mathematical modelling of plants, molecular genetics and ideotype conception.

International audience; In the ANR project “Archidemio” (2009 - 2012, SYSTERRA), we explored whether characteristics of the plant and the canopy (architecture, development, resistance levels) could be major determinants of epidemic development of air-borne diseases and could be used as control strategies in integrated plant protection. The project was structured in three main parts: 1) The construction of a generic model coupling host plant growth and fungal epidemics development, 2) the improvement of knowledge about four pathosystems (vine / powdery mildew, yam / anthracnose, peas / ascochyta blight, potato / downy mildew) and their characteristics (sensitivity to microclimate and susceptibility of the plant), and potential levers (genetic, or crop management), 3) the proposal of crop management scenarios at the plant level (architecture / genotype - ideotypes) and / or crop level (density, size, pruning).; Dans le projet ANR « Archidemio » (2009 – 2012, appel d’offre SYSTERRA), nous avons exploré si les caractéristiques de la plante et du couvert végétal (architecture, développement, niveaux de résistance) pouvaient être des déterminants majeurs du développement épidémique des maladies aériennes, et de leur maîtrise dans des stratégies intégrées de phytoprotection. Le projet était structuré en trois grands volets : 1) La construction d’un modèle générique couplant le développement de la plante et le développement épidémique de maladies aériennes fongiques, 2) L’acquisition de connaissances sur 4 pathosystèmes (vigne/oïdium, igname/anthracnose, pois/ascochytose, pomme de terre/mildiou) en fonction de leur caractéristiques (sensibilité au micro-climat et à la plante), et des leviers potentiels activables côté plante (génétique, conduite de la culture), 3) L’élaboration de scénarii de gestion au niveau de la plante (architecture / génotype - idéotypes variétaux) et/ou de la culture (densité, taille, tuteurage).

International audience; As any epidemic on plants is driven by the amount of susceptible tissue, and the distance between organs, any modification in the host population, whether quantitative or qualitative, can have an impact on the epidemic dynamics. In this paper we examine using examples described in the literature, the features of the host plant and the use of crop management which are likely to decrease diseases. We list the pathogen processes that can be affected by crop growth and architecture modifications and then determine how we can highlight the principal ones. In most cases, a reduction in plant growth combined with an increase in plant or crop porosity reduces infection efficiency and spore dispersal. Experimental approaches in semi-controlled conditions, with concomitant characterisation of the host, microclimate and disease, allow a better understanding and analysis of the processes impacted. Afterwards, the models able to measure and predict the effect of plant growth and architecture on epidemic behaviour are reviewed

Developing and implementing alternatives to the ‘pesticide only’ approach requires improvements in current pest control methods (using Decision Support Systems, longer rotations, more robust cultivars, mixed crops, crop management...), but also the generation of new knowledge that can be put to use in integrated and innovative crop production systems. Innovative studies are now needed that place the plant at the centre of the crop protection system; and, to do so, analyse how plant architectural traits can be used to limit or suppress disease epidemics. This topic is not new: it was indeed an important field of research before the advent of the ‘pesticide only’ approach that has dominated the practise of plant protection since the 1970s. Today there is a renewed impetus, firstly because of the societal pressure to develop environmentally friendlier pest control strategies, but also thanks to the advances in experimental and modelling activities which now allow truly interdisciplinary work when tackling complex systems. This volume puts together the main keynote papers delivered to the conference “Plant and Canopy Architecture Impact on Disease Epidemiology and Pest Development”, held in Rennes, France, in July 2012. The papers illustrate disciplinary complementarities, by including contributions from plant pathologists, disease epidemiologists, entomologists, agronomists, plant and crop physiologists, bioclimatologists, plant geneticists and appliedmathematicians.Many papers are co-authored by specialists from different disciplinary origins, highlighting the integrative efforts that need to be made to tackle a problem that may appear at first to be relevant only to plant pathologists. Why is such an interdisciplinary research strategy actually required? Simply, because the question at Eur J Plant Pathol (2013) 135:453–454 DOI 10.1007/s10658-012-0112-4

International audience; The spread of a pathogen within an anthropized crop plot depends on many factors acting at contrasted spatio-temporal scales. This is of paramount importance for vine and powdery mildew, one of its airborne pathogen. We aimed at developing a coupled PDEs-ODEs model for plant-pathogen interactions at the plot scale level in order to assess the effects of various host heterogeneities on the epidemic spread.

KEYNOTEKEYNOTE; Epidemics are dynamical processes with variable rates of disease progress. How much of these changes in disease rate are triggered by the host population is still a pending issue. An epidemic is driven by its effective reproduction number: the product between the proportion of susceptible tissue, the rate of disease transmission, and the duration of the infectious period. Then, any modification in the host population, either quantitative or qualitative (distribution of plants or of susceptible organs) may have an impact on the epidemic dynamics. The growth of the host population is modified by architectural features or by cultural or agronomical practices. The production of new organs continuously modifies the porosity of the plant or of the canopy and its level of susceptibility if organ susceptibility changes with age (ontogenic resistance). Indirectly, plant growth modifies the micro-climatic environment inside the canopy, generating favourable or unfavourable conditions for pathogens. The organ susceptibility, or their susceptibility period, may also be modified by cultural practices disrupting the crop-pathogen synchronisation. These variations within host populations do impact disease incidence, severity or spread. However, they have rarely been explicitly taken into account in epidemiological models. Tracking back from the global dynamics of an epidemic the pathogen processes that are impacted and ranking the host traits involved in their modifications represents a challenge. In this paper, we will 1) review evidence of epidemic variations attributed to plant growth and architecture in main pathosystems, 2) list the pathogen processes impacted, and give some clue to identify and assess them in different epidemic contexts and 3) explore models able to measure and predict the effect of plant growth and architecture on epidemics.

Keynote BKeynote B; Ideotypes are a popular concept for plant breeders, who designate as such the ideal combinations of traits in a particular genotype. This historical, genetic view of ideotypes can (and has) been more recently extended to cover the design of plant genotypes for specific cropping systems (the ‘agronomic’ view), or even the ideal combination of parameters, identified from simulation modeling, to a specific agronomic problem (the ‘mathematical’ view). Designing an ideotype requires first to precisely bind the purpose the ideotype is supposed to meet. This imposes not only the definition of the agronomic problem itself, the action possibilities available (genetic variability in the plant, human interventions during crop husbandry, etc…), but also of the production system considered. Whether ideotypes should remain virtual objects (i.e., cultivar blueprints) or can be real varieties is still an open debate. The different forms of ideotypes in turn induce different strategies for breeding plants. This paper will therefore briefly describe, analyse and discuss the application of these modes of ideotype conception and design in the specific case of architectural traits of plant and plant canopies to limit the epidemic development of pests and diseases in crops.

Corresponding author. Universidad de Talca, Facultad de Ciencias Agrarias, CITRA-CTVV, Avenida Lircay s/n, Talca, Casilla 747, Talca, Chile. ; fax: þ56 71 201695. E-mail address: hevaldes@utalca.cl; International audience; In various crop species, high levels of powdery mildew infection and severity have been associated with high vegetative vigour. In grapevine this relationship has also been observed by vine growers, though it has not been quantified. This study was undertaken to investigate the relationship between the development of powdery mildew on leaves and berries and canopy growth, and thus to quantify the relationship between the pathogen and its host. Over a two-year period (2005 and 2006), an experiment was carried out in a vineyard (cv. Aranel) near Montpellier, southern France. Several levels of canopy growth were generated by implementing four soil management strategies: i) perennial cover crop in the inter-row, ii) annual cover crop in the inter-row, iii) chemical weed control over the entire soil surface, iv) chemical weed control all over the soil surface and drip irrigation and fertilization in the row. Powdery mildew was artificially inoculated on experimental sub-plots with Erysiphe necator [Schw.] Burr. conidia. The most vigorous vines developed a larger number of diseased leaves and a higher percentage of mildewed berries compared to low-vigour vines. The major explanatory variable highlighted in these experiments was the shoot leaf number, mainly early in the season. A higher leaf population generated a larger number of powdery mildew colonies close to grapes and consequently a higher probability of berry infection. Our experimental results provide evidence of a positive relationship between powdery mildew development and grapevine vegetative development. These results provide an opportunity to develop new IPM strategies in vineyards

International audience; *Background and Aims : Epidemiological simulation models coupling plant growth with the dispersal and disease dynamics of an airborne plant pathogen were devised for a better understanding of host–pathogen dynamic interactions and of the capacity of grapevine development to modify the progress of powdery mildew epidemics. *Methods : The first model is a complex discrete mechanistic model (M-model) that explicitly incorporates the dynamics of host growth and the development and dispersion of the pathogen at the vine stock scale. The second model is a simpler ordinary differential equations (ODEs) compartmental SEIRT model (C-model) handling host growth (foliar surface) and the ontogenic resistance of the leaves. With the M-model various levels of vine development are simulated under three contrasting climatic scenarios and the relationship between host and disease variables are examined at key periods in the epidemic process. The ability of the C-model to retrieve the main dynamics of the disease for a range of vine growth given by the M-model is investigated. *Key Results : The M-model strengthens experimental results observed regarding the effect of the rate of leaf emergence and of the number of leaves at flowering on the severity of the disease. However, it also underlines strong variations of the dynamics of disease depending on the vigour and indirectly on the climatic scenarios. The C-model could be calibrated by using the M-model provided that different parameters before and after shoot topping and for various vigour levels and inoculation time are used. Biologically relevant estimations of the parameters that could be used for its extension to the vineyard scale are obtained. *Conclusions : The M-model is able to generate a wide range of growth scenarios with a strong impact on disease evolution. The C-model is a promising tool to be used at a larger scale.

International audience; For a better understanding of host / pathogen dynamical interactions and of the capacity of host development to modify disease progress, we devised epidemiological simulation models coupling plant growth with the dispersal and disease dynamics of an airborne plant pathogen. Our first model is a complex discrete deterministic model that explicitly incorporates the dynamics of host growth (e.g., distance between organs and their susceptibility) and the development and dispersion of the pathogen. The second one is a much simpler compartmental SEIR-like model. It takes into account the host growth with the foliar surface as unit of host growth and the ontogenetic resistance of the leaves. We compare the output of both models when applied to the specific system formed by the powdery mildew, Erysiphe necator, of grapevine.

International audience; The hypothesis that grey mould incidence would be positively correlated to grapevine canopy development was confirmed over a period of 3 years (2004–2006) on Aranel cultivar in an experimental vineyard near Montpellier, south France. Different levels of vine growth were generated by implementing three management schemes: (i) perennial cover crop, (ii) chemical weed control and (iii) irrigation and fertilisation. Grey mould incidence was assessed at harvest, together with various sets of variables linked with canopy microclimate, shoot vigour, vine capacity, cluster architecture, yield components and fruit composition. Significant positive correlations were observed between disease incidence and key variables of shoot vigour and vine capacity: total leaf number, leaf dry matter, leaf layer number, leaf area per metre of row, pruning mass and nitrogen accumulation. In 2004, Botrytis cinerea developed in all experimental plots because climatic and microclimatic conditions were conducive to grey mould. The climatic and microclimatic variables that significantly favoured grey mould development were: precipitation, duration of relative humidity >90% in the canopy and low potential evapotranspiration. However, in 2005 and 2006, under dry summer conditions, disease developed only in the most vigorous vines, which were both irrigated and fertilised. These vines showed a very high canopy growth, very compact clusters and a delayed fruit maturity. This evidenced that unfavourable climatic conditions for the disease development can be counterbalanced by conditions of high vine growth and associated canopy and cluster features.

International audience; An epidemiological model simulating the growth of a single grapevine stock coupled to the dispersal and disease dynamics of the airborne conidia of the powdery mildew pathogen Erysiphe necator was developed. The model input variables were either climatic (temperature, wind speed and direction) or related to the pathogen (location and onset of primary infection). The environmental input variables dictated plant growth and pathogen spread (latent period, infection, lesion growth, conidial spore production and release). Input parameters characterized the crop production system, the growth conditions and the epidemiological characteristics of the pathogen. Output described, at each time step, number, age and pattern of healthy and infected organs, infected and infectious leaf area and aerial density of spores released. Validation of the model was achieved by comparing model output with experimental data for epidemics initiated at different times of host growth. Epidemic behaviour for two contrasting years of crop development and 7 phenological stages at the time of primary infection (PI) was examined. For PI occurring at day 115 a vine with late budbreak (1998) showed 58% of primary leaves diseased at flowering compared with only 19% for a vine with early budbreak (2003). Depending on the phenological stage at PI (1-4 leaves), the proportion of diseased primary leaves decreased from 42% to 6% at flowering. Simulations suggested that differences resulted from the interplay between the timing of the first sporulation event, the phenological stage at the time of initial infection, and the age structure and spatial distribution of the leaf population.

International audience; Many actors in viticulture recognize the importance of potential quantitative relationships between susceptibility to fungal pathogens and grapevine growth or vigour. However, these relationships have been poorly documented in the literature. Some studies of grape quality have, incidentally, shown interactions between grey mould development and vegetative and reproductive growth patterns of grapevine. Our main objective was to find out which main variables characterizing canopy microclimate, grapevine vegetative and reproductive growth and fruit composition can best describe and quantify the effects on grey mould development

International audience

The spatiotemporal spreading of a fungal disease over a vineyard is investigated using a susceptible-exposed-infected-removed (SEIR)-type model coupled with a set of partial differential equations describing the dispersal of the spores. The model takes into account both short and long range dispersal of spores and growth of the foliar surface. Results of numerical simulations are presented. A mathematical result for the asymptotic behavior of the solutions is given as well.

International audience

This paper describes a parallel simulator for the propagation of a parasite in a vineyard. The model considers the structure, the growth and the susceptibility of the plant which play a major role in the development of the fungus and the spread of epidemic. Two spatial scales are distinguished for the dispersal of the parasite. We use both a realistic discrete model for the local dispersal, and a stochastic model for the long-range dispersal that averages the displacement of spores. An algorithmic description of the parallel simulator is given and real life numerical experiments on IBM SP3 are provided, that use up to 128 processors.

The effects of powdery mildew (Uncinula necator) on grape yield, juice and wine quality were quantified for cultivar Cabernet Sauvignon (CSa) in 1997 and 1999, and for Sauvignon blanc (Sa) in 1999. Analyses were carried out on batches of healthy berries to which known percentages (0–50%) of diseased berries were added, and on natural clusters that were classified into four visual classes from low (C1) to high (C4) disease severity. CSa diseased berries showed an average weight reduction of 12% (1997) and 20% (1999). The direct consequence of a higher percentage of smaller, diseased berries was a reduction in yield. The accompanying loss of weight in must from C1 to C4 clusters increased from 10 to 45%. Sugar content in diseased berries was not significantly different from disease-free berries in 1997, but was 20–21% (CSa) and 14% (Sa) higher in 1999. Severely infected batches also showed a higher total acidity than healthy ones. The total anthocyanin content of CSa was decreased by 0·91% (1997) and 0·66% (1999) per percentage mildewed berries added by weight. In Sa wines the concentration of 3-mercaptohexanol, a component of varietal aroma, was decreased by powdery mildew. Multidimensional analyses, based on all the variables studied, successfully grouped batches of CSa according to disease severity. Using directional triangular tests wine experts were able to recognize CSa wines produced from berries with ≈25% of powdery mildew; the threshold for nonexperts was 50%. CSa wines obtained from samples with more than 30% of diseased berries by weight were significantly classified as the worst according to preference order criteria, but below this value the preference was not significant. Sa wines with

One major gene for resistance to isolate WYR 85-22 of race 6E0 of Puccinia striiformis was identified by genetic analysis of the differential cultivars Heines Peko, Strubes Dickkopf and Heines VII. This gene was different from Yr2Yr6 already identified in Heines Peko (Yr2Yr6) and Heines VII (Yr2), was allelic in the three cultivars and also to a gene expressed in the other differentials Reichersberg 42 (Yr7) and Clement (Yr9). In Heines Peko, Strubes Dickkopf and Heines VII, a minor gene was also postulated, which, it is proposed, gave only a low level of resistance by itself but strengthened the expression of the major gene when the latter was homozygous or heterozygous. The genetics of the resistance was analysed using six resistance classes and applying multidimensional analyses. The number of resistance genes was hypothesized using data from F3 families from crosses between the three differentials and the cultivar Heines Kolben, which is susceptible to this race.

Genetic data showed that a common gene was present in the three differential wheat cultivars Heines VII (Yr2), Heines Peko (Yr2, Yr6) and Heines Kolben (Yr6) expressed against the race 109E9 of Puccinia striiformis which possesses virulence for Yr6 and avirulence for Yr2. This supported the hypothesis that Heines Kolben carries the gene Yr2 in addition to Yr6 for resistance to yellow rust in a genetic background in which Yr2 is weakly expressed in seedlings. F1, F2 and F3 progenies from the cross Heines Kolben × Peragis confirmed the monogenic segregation of Yr2 in Heines Kolben and demonstrated the variation of its expression with environmental conditions.

An inducer race ofPuccinia striiformis inoculated two days before a challenger race on wheat seedlings of cv. Clement, reduced infection efficiency by 44% and lesion expansion by 7.7%; there was no effect on sporulation rate. In field epidemics, induced resistance restricted the disease intensity on cvs. Clement and Austerlitz in pure stands by 44% and 57% respectively. In the glasshouse at the seedling stage, disease intensity in a varietal mixture was reduced by 82% compared to the susceptible pure stands; one third of the total disease reduction was attributable to induced resistance.

Contact: http://www.esa.org.pl/; International audience; The extensive use of pesticide products for protecting grapevine against pathogens such as grey mold and powdery mildew can result in the pollution of superficial and subterranean waters, To face this problerm, integrated pest management systems have been developped in vineyards. They are generally based on epidemiological models (1) and of\on observations of attacks in the vineyard. However, they do not take into account the state of the canopy, i.e. its growth and architecture. Nevertheless, vinegrowers and pathologists recognise the importance of the relationships between vine vegetative vigour and sensitivity to fungi attacks (2) although these relations are poorly documented in the litterature. For example, experiments carried out in France on grapevine cv Chenin showed a high positive correlation between Botrytis cinerea symptoms and vine vigour (expressed as weight of pruned canes) (3). In this context, the objective of this study was to investigate the possible positive relationship between grapevine vigour and the final level of grey mold and powdery mildew

National audience

Articles correspondant à plusieurs colloques organisés dans le cadre des séminaires du CTPS en 2012.; International audience; Grapevine downy mildew is one of the most damaging diseases for viticulture and it is currently controlled with fungicides. A cost-effective and environmentally friendly alternative to the use of chemicals is using resistant grapevine varieties. However, all European cultivated grapevine varieties are susceptible to downy mildew, so the résistance needs to be introduced from resistant grapevines through breeding programmes aiming at obtaining durable résistance while maintaining the desired agronomical and quality traits. In the year 2000, the French Institute for Agronomical Research (INRA) got involved in a selection program with the goal of creating grapevine varieties bearing durable resistance. Joint Research Units UMR 1131 (SVQV, Colmar) and UMR 1065 (SAVE, Bordeaux) work together in a collaborative research project built around five interconnected research lines that, each one at its level, provide knowledge essential for the durable management of grapevine resistances. The first results emerging from this join project show clearly that the European populations of grapevine downy mildew are able to adapt and overcome grapevine varieties carrying monogenic resistances. These resistance-breaking risks should be taken into consideration when building selection schemes aiming at obtaining new grapevine varieties.; Le mildiou est une des maladies les plus importantes qui affectent à la vigne. La stratégie actuelle de lutte contre cette maladie est l’utilisation de fongicides. Une alternative, économique et respectueuse de l’environnement, est l’utilisation de variétés de vigne résistantes. Cependant, toutes les variétés de vignes cultivées européennes sont sensibles au mildiou et la résistance doit être introduite à partir de vignes résistantes à travers un programme d’amélioration qui garantisse le maintien des caractéristiques désirables et une résistance durable. L'INRA s'est engagé en 2000 dans un projet de sélection visant à créer des variétés à résistances durables. Les UMR 1131 (SVQV, Colmar) et UMR 1065 (SAVE, Bordeaux) de l’INRA mènent un projet de recherche en collaboration sur cinq axes de recherches qui s’alimentent les uns les autres et qui, chacun à leur niveau, contribuent à produire les connaissances indispensables à la gestion durable des résistances de la vigne. Les premiers résultats issus de ce projet montrent clairement que les populations de mildiou européennes sont capables de s’adapter et de contourner les variétés à résistance monogénique. Ces risques de contournements sont à prendre en considération dans la construction des schémas de sélection des nouvelles variétés de vigne.