Thèses sur le sujet « Plantes – Maladies cryptogamiques – Épidémiologie »
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Raymondaud, Hubert. « La tavelure du mirabellier : étude biologique et épidémiologique de Cladosporium carpophilum et mise au point d'une méthode de lutte raisonnée ». Vandoeuvre-les-Nancy, INPL, 1988. http://www.theses.fr/1988NAN10413.
Texte intégralGrosdidier, Marie. « Épidémiologie de la chalarose du frêne, une maladie causée par l’agent pathogène Hymenoscyphus fraxineus ». Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0151/document.
Texte intégralIntroduction of invasive pathogen fungi is a major cause of forest diseases emergence. For 30 years, a dieback has severely affected ashes and in particular Fraxinus excelsior. The pathogenic fungus causing the disease is an ascomycete originating from Eastern Asia, Hymenoscyphus fraxineus. It was observed for the first time in 90’s in Poland, then rapidly spread over Europe and was reported in France in 2008. The disease is mainly spread by airborne ascospores. The aim of this thesis is to study the epidemiology of H. fraxineus dispersal by determining environmental factors which impact pathogen development, and by proposing a dispersal model of the disease. The first objective of this thesis was to improve the trapping method of airborne inoculum and then, to use it to study the dispersal pattern of H. fraxineus. An experiment was set up to confirm the reliability of the molecular biology test for low levels of target such as these observed at the disease front. This trapping method of airborne spores was then compared to maps of disease presence deriving from symptoms reports on ashes. The study was realized at different scales, landscape (village) and regional, with sampling area of about 100 km at the disease front. This work enabled us to determine a radius around inoculum source that would have to be manage for effectively limit the disease development. The second objective of the thesis aimed at determining environmental factors which influence disease development, which is an important issue for forest management and future of ashes in the next decade. We have shown that high host density and high humidity both positively impact disease development. This work confirmed the pathogen susceptibility to high summer temperatures in natural settings and suggests that the climate of Southeastern France should limit disease development. At a larger scale, climate change may work in favor of ashes. Moreover, an Allee effect presence in the population dynamic of H. fraxineus was suggest by our experimental results. The last objective of this thesis was to model the disease spread in France. Our works estimated the spread speed to 60 km per year. A reaction-diffusion model was developed to link dispersal disease according to H. fraxineus population dynamic and environmental factors which impact its development. This dispersal model which can use standard data of French forest health surveillance system will provide new knowledge useful to implement management strategies. This thesis offers perspectives on the future of ashes in a context of climate change and more broadly about the management of biological invasions
Laubray, Simon. « Facteurs déterminants de la production d’inoculum chez Hymenoscyphus fraxineus, agent de la chalarose du frêne ». Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0381.
Texte intégralPopulations of common European ash (Fraxinus excelsior) are currently suffering from the chalarosis epidemic. The first ash dieback was reported in the early 1990s in Poland following the introduction of the pathogenic fungus Hymenoscyphus fraxineus, which originated in north-east Asia. In 2022, the epidemic had spread over most of the range of F. excelsior, causing significant mortality. The impact of the pathogen is all the greater when the infection is massive. This thesis therefore focuses on the pathogen's source of inoculum in leaf litter debris. The aim is to gain a better understanding of the demographic and environmental factors that determine inoculum production. The first axis focuses on the population dynamics of H. fraxineus in relation to the density of its host and the density dependent on inoculum production. This fungus multiplies exclusively by sexual reproduction, with conidia playing the role of spermatia. As they are dispersed over a distance of just a few dozen centimetres, reproductive success is highly dependent on the probability of sexual partners meeting, which in turn depends on the pathogen's population density. Fruiting body production (from sexual reproduction) was monitored as a function of H. fraxineus population density in a network of stands following an ash density gradient. This section highlighted, on the one hand, a population density of H. fraxineus closely linked to host density and, on the other hand, a limited production of inoculum at low population density. This density dependency at low numbers is known as the Allee effect. The second axis estimates the persistence of the pathogen in contaminated stands and changes in its capacity to produce inoculum over time. This persistence is an essential factor to take into account in eradication, but also in understanding the population establishment mechanism. The system installed in ash stands was used to monitor the degradation kinetics of ash litter as a function of its rate of colonisation by H. fraxineus, as well as the fungus' fruiting potential depending on the age of the litter during degradation. The persistence of litter colonised by the pathogen for at least three years and the ability of the pathogen to fructify during this period is proof that a reservoir of inoculum has been established on a long-term basis in contaminated stands. This reservoir of inoculum could play a decisive role in relaunching an epidemic after a year in which foliar infection is unfavourable. The third axis describes the fungal communities present in the decomposing ash litter in which H. fraxineus continues to develop after the colonised leaves have fallen. Using fungal ITS1 metabarcoding data, the study compares the fungal communities present on the leaves at the time of their fall in autumn and the fungal communities present on the leaf residues in spring. Changes in the abundance of each species in the fungal community were compared with those of H. fraxineus. The species identified as having an abundance negatively correlated with the abundance of H. fraxineus could have an antagonistic effect on the winter development of the pathogen, thus limiting its presence the following spring and reducing its inoculum production capacity. The work carried out highlights the importance of considering the diversity of factors involved in inoculum production. These factors may be decisive in the establishment of a population of the invasive pathogen studied in ash stands
Luini, Estelle. « Implication de toxines fongiques dans l'esca de la vigne, mise au point d'un test de diagnostic et recherche d'un traitement contre la maladie ». Poitiers, 2007. http://www.theses.fr/2007POIT2306.
Texte intégralEsca is a vascular disease very harmful to the vine since it causes long term stock death. This complex disease involves several pathogenic fungi among which Phaeomoniella chlamydospora and Phaeoacremonium aleophilum are viewed as the first invader fungi. The above mentioned fungi secreted several toxic molecules into their culture medium. Applied to grapevine cells, these molecules act on key stages of plant responses to pathogenic agents namely: modifications of membrane potential, proton fluxes, nutrient absorption and induction of cell death. These modifications have been linked with changes in enzyme activities controlling the following processes: H+-ATPase of the plasma membrane, NADPH oxidase and phenylalanine ammonia-lyase. The polypeptidic nature of certain compounds secreted by P. Chlamydospora and P. Aleophilum enabled us to obtain polyclonal antibodies directed against these polypeptides which were subsequently used for the optimisation and validation of a dot-blot method. This simple test could distinguish between infected and non-infected plants. This test was initially validated on grapevine cuttings grown in a greenhouse and which were inoculated selectively by each fungus. The test was then used in a vineyard on plants in the presence or absence of foliar esca symptoms. A treatment against esca was developed by either mixing molecules having antifungal action or inducing plant defence reactions. After verification of the antifungal activity of the association on P. Chlamydospora and P. Aleophilum on an in vitro culture, a treatment was evaluated in a greenhouse by foliar pulverization on grapevine cuttings inoculated selectively. The efficiency of the treatment was monitored by using the dot-blot method
Daugrois, Jean-Heinrich. « Les beta-1, 3-glucanases du haricot : leur implication dans la résistance à l'anthracnose ». Toulouse 3, 1989. http://www.theses.fr/1989TOU30166.
Texte intégralGosme, Marie. « Modèlisation du développement spatio-temporel des maladies d’origine tellurique ». Rennes, Agrocampus, 2007. http://www.theses.fr/2007NSARA049.
Texte intégralSoilborne diseases are difficult to control by fungicides or resistant cultivars ; they are characterized by processes and spatio-temporal scales that can be different from those of aerial pathogens. In particular, the dispersal processes of soiborne pathogens result in the appearance and persistence of strong spatial patterns, namely disease foci. Aggregation inflences both the temporal dynamics of diseases and their relation to crop losses thus making spatial pattern an important factor when assessing control methods. The objectives of this study were to understand and model the spatio-temporel develoment of soilborne epidemics in order to determine control strategies that may reduce disease risk through an effect on spatial pattern. To that end, two models were developed. The first one is spatially explicit and biologically realistic ; its parameters were measured for take-all disease of wheat. The model was tested with field data ; this showed that the model is precise but overestimates disease development. This test also provided possible avenues for improving the predictive ability of the model. The second model is simpler and more genetic ; it uses hierarchy theory in order to simulate disease spread across multiple spatial scales. Hypotheses concerning the behaviou of epidemics and the relationships between disease incidences at different spatial scales culd be tested using this model for example the effect of the host and inoculum spatial structures on disease dynamics and aggregation. In the case of take-all disease of wheat –for which we have demonstrated the importance of the spatial pattern of primary inoculum- the simulation results advocate for different sowing patterns according to the rank of consecutive wheat crops
Jaber, Rim. « Défenses naturelles des plantes : identification de nouveaux stimulateurs de défenses des plantes (SDP) capables d'améliorer la résistance du lin contre le champignon Fusarium oxysporum ». Rouen, 2016. http://www.theses.fr/2016ROUES059.
Texte intégralPlants are surrounded by a diverse range of microorganisms that can cause serious crop losses and requires the use of pesticides. Flax is a major crop in Normandy and is regularly challenged by the pathogenic fungus Fusarium oxysporum (Fo) f. Sp. Lini. In order to protect themselves, plants use “innate immunity” called M/PTI (Microbe/Pathogen-Associated Molecular Patterns Triggered Immunity) as a first defense line against pathogens. Plants are able to perceive pathogens by the recognition of conserved motifs on the surface of the pathogens (M/PAMPs), by transmembrane protein receptors (PRRs, Pattern Recognition Receptors). The use of elicitors able to mimic M/PAMPs and activate plant defense may be an alternative for plant protection that could minimize the use of pesticides. Based on this, previous work was conducted by screening a chemical library of 1600 compounds and has allowed the identification of five compounds able to activate defense responses in Arabidopsis thaliana. During my PhD thesis, we tested those five compounds on their abilities to improve resistance of two commercially available flax varieties used for their fibers against F. Oxysporum, responsible of the vascular wilt. The data show that two of them, holaphyllamine (HPA) a natural compound and M4 a synthetic one, did not affect flax growth up to 10 μM. In addition, they did not have any negative effects on F. Oxysporum development and spores germination at the tested concentrations (up to 10 μM). Cell imaging analyses showed that HPA and M4 at 1 μM can induce oxidative burst as well as callose deposition in flax, a well-known marker of PAMP-elicited defense mechanisms. Furthermore, transcriptomic analyses showed that HPA and M4 induced changes in the expression patterns of two pathogenesisrelated (PR) genes (PR-2 and PR-3) coding for a β-(1,3)-glucanase and an endo-chitinase, respectively. These enzymes can degrade the fungal cell wall and stop its growth. Finally, flax plants pre-treated with HPA and M4 before infection with Fo f. Sp. Lini exhibited a decrease in the foliar disease symptoms by more than 50 % and 70 %, respectively. Together, these findings demonstrate that HPA and M4 are elicitors as they are able to activate defense responses in flax plants that lead to improving its resistance against Fo infection
Subileau, Corinne. « Systématique et biologie du complexe parasitaire constitué du Phyllachora torrendiella (Bat. ) nov. Comb. Et du Botryosphaeria cocogena nov. Sp. , agents fongiques du dessèchement foliaire du cocotier au Brésil ». Paris 6, 1993. http://www.theses.fr/1993PA066645.
Texte intégralMouly, Anne. « Recherche de marqueurs moléculaires de la tolérance du tournesol à Sclerotinia sclerotiorum ». Toulouse 3, 1990. http://www.theses.fr/1990TOU30082.
Texte intégralDiop-Bruckler, Marguerite. « Détection précoce de Ceratocystis fimbriata F. Platani, agent du chancre coloré du platane, par le test Elisa ». Montpellier 2, 1991. http://www.theses.fr/1991MON20020.
Texte intégralIoos, Renaud. « Caractérisation génétique de Phytophthora alni Brasier & ; S. A. Kirk, hybride interspécifique agent du dépérissement de l'aulne en Europe ». Nancy 1, 2006. http://docnum.univ-lorraine.fr/public/SCD_T_2006_0105_IOOS.pdf.
Texte intégralAn emergent disease of alder is caused by a complex of three taxa belonging to the genus Phytophthora (Oomycetes): P. Alni subsp. Alni (Paa), P. Alni subsp. Multiformis (Pam) and P. Alni subsp. Uniformis (Pau). The first part of this study focused on the development of specific detection tools for these three taxa. Based on SCARs generated with RAPD, we designed three PCR primer pairs which can be combined to specifically detect and identify Paa, Pam and Pau in different substrates (plant tissue, water, soil). Second, we studied the occurrence and the allelic distribution for several nuclear single-copy genes containing introns on a wide collection of P. Alni and close species. Mitochondrial DNA was also studied through RFLP and gene sequencing. We demonstrated that i) Pau may not result from a hybridization event, ii) two divergent alleles for each of the nuclear genes are observed in Pam, which suggests this taxon may have been generated by a reticulation or by autopolyploidisation, iii) Paa combines the alleles observed in Pam and Pau and was probably generated by hybridization between Pam and Pau or Pam- and Pau-like taxa. In addition, we studied the expression of elicitin genes, a multigenic family specific to the genus Phytophthora. The cumulative patterns of Pau and Pam in regard with Paa confirmed our first results. Last, in order to study the genetic variability of the different taxa, microsatellite markers were isolated in Paa and characterized. The genotypes we resolved demonstrate a low level of variability for the three taxa. They confirm our hypotheses in regard with Paa origin and suggest that Pam is also an allopolyploid taxon
Guyot, Jean. « Analyse, à petite échelle, de l’influence de l’environnement, de l’inoculum et de l’hôte sur la dynamique épidémique de la maladie sud-américaine des feuilles de l’hévéa (Microcyclus ulei) en milieu amazonien ». École nationale supérieure agronomique (Montpellier), 2007. http://www.theses.fr/2007ENSA0027.
Texte intégralThébaud, Gaël. « Etude du développement spatio-temporel d'une maladie transmise par vecteur en intégrant modélisation statistique et expérimentation : cas de l'ESFY (European stone fruit yellows) ». Montpellier, ENSA, 2005. http://www.theses.fr/2005ENSA0028.
Texte intégralEmerging and re-emerging diseases can give rise to serious economical - and even social - crises. Improving the knowledge that allows coping with such diseases is an immediate stake in this field of research. An approach to this issue is proposed and applied to European stone fruit yellows (ESFY), a disease of Prunus trees that re-emerges in Europe. This disease is responsible for an incurable decline, mainly on apricot and Japanese plum. It is caused by a phytoplasma ('Candida/us Phytoplasma prunorum') specifically transmitted by Cacopsylla pruni on the persistent mode. Wc analysed the risk factors and the processes of ESFY epidemics through integrating several approaches: a statistical model at a regional scale for analysing the factors correlated to ESFY prevalence, experiments on the cycle of the vector and on the potential infectivity of its different stages, and hypothesis tests based on the location of diseased trees. The statistical approaches highlight the major impact on disease dynamics of the cultivar/rootstock combination. The experiments demonstrate that C. Prumi is a univoltine vector whose young stages acquire the phytoplasma, multiply it, and then conserve it during their summering and overwintering on conifers (alternative hosts). In the most probable scenario arising from the comparison of the different approaches, the reimmigrants infected since the year before would be the only efficient vectors of ESFY in apricot orchards, where they would land at random and independently; then, they would often perform several short-distance primary inoculations: therefore, this disease would be monocyclic in apricot orchards. This scenario was incorporated into a simulation model at the orchard scale, which, in the future, will unable estimating the parameters linked to the local behaviour of the vector
Calenge, Fanny. « Organisation génomique globale des facteurs de résistance à la tavelure (Venturia inaequalis), à l'oi͏̈dium (Podosphaera leucotricha) et au feu bactérien (Erwinia amylovora) chez le pommier (Malus x domestica) ». Angers, 2004. http://www.theses.fr/2004ANGE0002.
Texte intégralThe purpose of this thesis was to determine the genomic organization of resistance factors in apple. We first constructed a genetic linkage map of an apple progeny. Then we studied the genetic determinism underlying partial resistance to scab, powdery mildew and fire blight in three progenies through a QTL analysis. At last, candidate genes presumably involved in resistance or defense against pathogens were mapped. The disease resistance factors identified during this study, and additional resistance factors (QTL and major genes) identified during previous studies were located on the same synthetic genetic linkage map. Most resistance factors were organized in clusters. Several co-localizations between QTL, candidate genes, and major genes occured, which led us to formulate some hypotheses about the putative functions of the genes and QTL mapped. From these results, strategies to create apple varieties carrying multiple resistances may be defined
Gibert, Caroline. « Génération de fissures cuticulaires sur la pêche (Prunus Persica (L. ) Batsch) en réponse à des opérations culturales : conséquences pour la qualité et la contamination par les monilioses ». Avignon, 2007. http://www.theses.fr/2007AVIG0604.
Texte intégralBased on experiments realized two years on nectarine fruits grown under various cultural conditions (variable fruit crop loads an irrigation regimes), we quantified cuticular cracks and examined by a modelling approach their contribution to fruit quality via the surface conductance to water vapour diffusion and to fruit contamination by brown rot. Cuticular cracks occur during the final swelling of the fruit and represent up to 12,5% of its surface area when its growth rate is high. They preponderantly participate to conductance (up to 85%) and fruit infection by M. Laxa. The evolution of conductance of its components and of cuticular crack surface area driven by fruit growth and the probability of fruit infection in relation with the cuticular crack surface area and the conidial density were modelled and the equations integrated into an existing "virtual fruit" model simulating organoleptic quality traits. This combined model was used to evalutate technical scenarios, emphazing fruit organoleptic quality, storage potential and environmental quality. Scenarios including water stress offer a good compromise but require an evolution of market standards
Marçais, Benoît. « Influence de facteurs de l'environnement sur le développement de l'encre du chêne rouge (Quercus rubra L. ), maladie provoquée par Phytophthora cinnamomi ». Nancy 1, 1992. http://docnum.univ-lorraine.fr/public/SCD_T_1992_0217_MARCAIS.pdf.
Texte intégralHabrylo, Olivier. « Une E. S. T. (Expressed Sequence Tag) conduit à la caractérisation, chez le houblon (Humulus lupulus), de trois inhibiteurs de xyloglucanase dont l’expression est influencée par des facteurs biotiques et abiotiques ». Strasbourg, 2011. http://www.theses.fr/2011STRA6143.
Texte intégralPhytopathogenic fungi secrete a powerful arsenal of enzymes potentially active on each polysaccharide layer of the plant cell. As a first line of defense, plant cell walls contain several inhibitors to specifically inhibit the activity of these microbial enzymes. In the present study we describe the identification and characterization of three xyloglucan-specific endoglucanase inhibitor proteins (XEGIPs) from hop (Humulus lupulus). Some evidences have been accumulated about the role of these XEGIPs in plant defense. Starting from an expressed sequence tag three genes were isolated by the rapid amplification of cDNA ends, cloned and corresponding proteins expressed in insect cells. The functions of the proteins were validated by enzymatic activity measurements were performed with xyloglucan as substrate. Inhibitor n°1 and inhibitor n°2 were shown to inhibit the hydrolytic activity of xyloglucan-specific endoglucanase from the fungi Aspergillus aculeatus and Fusarium graminearum. The investigation on target enzymes lead to production, expression and characterization of four unknown GH12 from F. Graminearum. Real-time PCR have shown variations in the spatial distribution of inhibitors and differential expression between hop cultivars. The main lines are the following : inhibitor n°1 is expressed as a result of wounding and inhibitor n°2 is inducible by F. Graminearum. Inhibitor n°3 could be have a physiological function with a positive regulation during the germination stages and in the female hop cones
Durup, Valérie. « Le vin de Chablis ». Paris 5, 1994. http://www.theses.fr/1994PA05P014.
Texte intégralKozlowska-Makulska, Anna. « Variabilité biologique et moléculaire des polérovirus responsables de la jaunisse modérée de la betterave sucrière en Pologne et en France ». Université Louis Pasteur (Strasbourg) (1971-2008), 2008. https://publication-theses.unistra.fr/restreint/theses_doctorat/2008/KOZLOWSKA-MAKULSKA_Anna_2008.pdf.
Texte intégralCe travail de thèse sur la variabilité des polérovirus de la betterave (Beet mild yellowing virus et Beet chlorosis virus) avait quatre objectifs scientifiques : 1° une étude épidémiologique comparée de la jaunisse modérée de la betterave en France et en Pologne dont les résultats ont montré pour la première fois la présence du BChV en Pologne et confirmé la progression du BChV en France, ainsi que la fréquence croissante de co-infections BChV-BMYV. Lors de cette étude, des échantillons de betterave rouge, ainsi que d’adventices, ont également été trouvés infectés par des polérovirus de la betterave dans respectivement 14 sur 158 et 20 sur 99 plantes ; 2° une caractérisation moléculair des isolats polonais en comparaison avec des isolats français, suivie d’une analyse phylogénétique qui a permis d’identifier des isolats recombinants de BChV, chez lesquels la séquence de la CP était reliée phylogénétiquement à celle du BMYV; 3° une analyse de la spécificité de transmission de différents isolats du BChV et du BMYV par quatre espèces aphidiennes qui a révélé un fort taux de transmission par Myzus persicae et Macrosiphum euphorbiae et une absence de transmission par Aphis fabae et Myzus ascalonicus. De plus, une variabilité d’efficacité de transmission parmi les isolats du BChV a été obtenue avec deux clones de M. Euphorbiae ; 4° une évaluation du degré de la suppression du PTGS (post-transcriptional gene silencing) qui a montré que la protéine P0 du BMYV est un suppresseur de PTGS très efficace hors de son contexte viral. Par contre, dans les mêmes conditions expérimentales, la P0 du BChV n’a montré aucun effet de suppression du RNA silencing. De plus, pour deux isolats du BMYV, la P0 n’a pas induit de suppression du silencing
Allorent, Delphine. « Analyse et modélisation épidémiologique de la tache angulaire du haricot ("Phaseolus vulgaris") due à "Phaeoisariopsis griseola" ». Montpellier 2, 2005. http://www.theses.fr/2005MON20041.
Texte intégralBenizri, Emile. « Mise au point d'un modèle de simulation et de prévision de la rouille brune du blé ». Toulouse, INPT, 1989. http://www.theses.fr/1989INPT011A.
Texte intégralSakr, Nachaat. « Analyse du coût de virulence chez Plasmopara halstedii, l'agent du mildiou du tournesol ». Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2008. http://tel.archives-ouvertes.fr/tel-00729681.
Texte intégralPetitprez, Michel. « Pouvoir pathogène et épidemiologie de Exserohilum turcicum, parasite du mai͏̈s ». Toulouse, INPT, 1989. http://www.theses.fr/1989INPT027A.
Texte intégralBerger, Pascale. « Les composés phénoliques foliaires de l'hévéa et leur implication dans la résistance à "Colletotrichum gloeosporioides" Penz. Et "Microcyclus ulei" Henn ». Montpellier 2, 1992. http://www.theses.fr/1992MON20062.
Texte intégralValdès, Gomez Hector. « Relations entre états de croissance de la vigne et maladies cryptogamiques sous différentes modalités d’entretien du sol en région méditerranéenne ». Montpellier, ENSA, 2007. http://www.theses.fr/2007ENSA0012.
Texte intégralOuattara, Alassane. « Épidémiologie moléculaire des géminivirus responsables de maladies émergentes sur les cultures maraîchères au Burkina Faso ». Thesis, La Réunion, 2017. http://elgebar.univ-reunion.fr/login?url=http://thesesenligne.univ.run/17_52_AOuttara.pdf.
Texte intégralGeminiviruses have emerged to become one of the largest and most economically important groups of plant-infecting viruses, and geminivirus-induced diseases are a major threat to worldwide vegetable production, particularly in tropical and subtropical regions of the world. Importantly, the accumulated body of work on some of the most important geminiviral associated diseases clearly demonstrate the role of geminiviruses associated with wild plants on the emergence of disease on imported crops. Moreover, recent metagenomic data suggested that the vast majority of viruses characterized from crops represent only a small fraction of the phytoviruses in general. It is therefore of prime interest to obtain a better knowledge of viral diversity infecting crops and wild plants, the main epidemiological parameters involved in their emergence and their dynamic at the scale of agro-ecological systems. In this work, a survey of solanaceous crop fields and their surrounding uncultivated plants from 48 localities in Burkina Faso and Ivory Coast was performed. The sample analysis using classical molecular biology tools both confirm the incompleteness of our knowledge of the geminivial diversity and the existence of numerous alternative wild host plants. At least five species of begomovirus and mastrevirus were found in association with the ToLCD-TYLCD. A North to South increasing gradient of complexity of viruses populations was uncover with PepYVMLV being the most prevalent on cultivated solanaceous plants. The discovery of the association of a newly described DNA-B component with the PepYVMLV also lead to the study of the epidemiological parameters of this co-infection. Despite this association being relaxed, it was demonstrated that the virulence of the disease, the viral accumulation and the transmission by Bemisia tabaci were increased with the presence of the co-infection with the DNA-B component. All these factors are probably associated with the success of this association on the field. Because of the extreme severity of the resulting disease, the diffusion of this new DNA-B component at a larger scale would represent a major threat to tomato culture in Burkina Faso, Africa and the world in general. The use of a metagenomic approach, allow the generalization of our findings to full agro-ecological settings. Besides confirming previous species discovery, species yet undescribed in Burkina Faso along with completely new begomovirus species were described. The inspection of the virus-plant and virus-virus associations networks allow to uncover strong links existing between the viral corteges associated to groups of cultivated and uncultivated plants. These findings emphasized the necessity to consider full agro-ecological settings plant diversity rather than only crops in order to understand and prevent geminiviruses associated diseases. Globally, our results highlight the necessity to carry on the ongoing plant disease monitoring work and the inventory of viral populations associated with cultivated and uncultivated plants in order to understand the functioning of natural geminiviral community and the impact of human practices on the emergence of viral disease
Delanoë, Olivia. « Les ressources génétiques des passiflores de Guyane : amélioration de la culture des fruits de la Passion ("Passiflora edulis f. flavicarpa" Degener, Passifloraceae) ». Montpellier 2, 1992. http://www.theses.fr/1992MON20154.
Texte intégralFaugeron, Sylvain. « Épidémiologie, biologie et génétique des populations de Mazzaella laminaroïdes (Rhodophyta) infectée par Endophyton sp. (Chlorophyta) et Pleurocapsa sp. (Cyanobacteria) ». Lille 1, 2002. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/2002/50376-2002-55.pdf.
Texte intégralTourte, Catherine. « Epidémiologie de Pseudomonas syringae PV. Phaseolicola et mise au point de la PCR pour sa détection ». Lyon 1, 1993. http://www.theses.fr/1993LYO10148.
Texte intégralChartrain, Laætitia. « Gènes de résistance spécifique et partielle à la septoriose du blé (Mycosphaerella graminicola) ». Toulouse, INPT, 2004. http://www.theses.fr/2004INPT004A.
Texte intégralMoura, Luísa. « Diversité génétique et phénotypique ches P. Corrugata et P. Mediterranea, agents de la moëlle noire de la tomate : importance de la colonisation asymptomatique et de la température dans le développement de la maladie ». Angers, 2006. http://www.theses.fr/2006ANGE0047.
Texte intégralPhenotypic and pathogenic characterization of 84 strains isolated from tomato with symptoms of pith necrosis (TPN) in Portugal, showed that P. Corrugata, P. Mediterranea, P. Viridiflava and fluorescents Pseudomonas "oxydase positive", are the most imortant bacteria associated with the etiology of this disease. We discovered that, together with P. Cichorii, P. Marginalis is also a pathogen of TPN. Numerical analysis of 119 phenotypic characteristics placed the majority of the isolates in two distinct groups corresponding to P. Corrugata and P. Mediterranea species. Comparing these results with multiplex-PCR identification, we found four distinct profiles within P. Corrugata, some of strains sharing characteristics of P. Mediterranea. Consequently, we propose that the 2-ketogluconate to be no longer used as a discriminant substrate of these two species. The genetic diversity of 63 strains of P. Corrugata and P. Mediterranea evaluated by REP, ERIC and BOX-PCR, and by the ITS-HMA technique, allowed discrimination of three genetic groups corresponding to P. Corrugata and P. Mediterranea species, and a new genetic group, consisting of portuguese strains only (Pmc). Together with DNA-DNA hybridization studies, these results suggested the existence of new Pseudomonas species or sub-species. Bio-PCR used to detect and monitoring populations of P. Corrugata, P. Mediterranea, Pmc and P. Viridiflava in the soil and on tomato tissues in the absence of symptoms, provided new information on the epidemiology of the disease
Pionnat, Sandrine. « Recrudescence du crown gall du rosier : caractérisation biochimique et moléculaire d'une population d'Agrobacterium tumefaciens et implications de la systémie de la bactérie dans l'épidémiologie de la maladie ». Lyon 1, 1997. http://www.theses.fr/1997LYO10091.
Texte intégralHouillon, Ismaël. « Modélisation du paysage agricole et inférence du risque pour l'accompagnement des réseaux d'épidémiosurveillance : application au paysage agrumicole réunionnais ». Thesis, La Réunion, 2022. http://www.theses.fr/2022LARE0014.
Texte intégralPlant disease surveillance is a major food safety issue. Although surveillance methods have been greatly improved in the last decade, especially with risk-based surveillance, implementing effective surveillance is not obvious in some regions. Reunion Island is an excellent example of such territories where organizing plant disease surveillance is a challenge due to its position as a DROM, with a very heterogeneous landscape and limited resources. Since 2012, Huanglongbing (HLB), caused by the bacterium Candidatus Liberibacter, is re-emerging in citrus orchards in Reunion Island and the state services have to organize the surveillance of a fragmented, heterogeneous citrus landscape and this taking into account local policies. We will show here the methods developed to improve the knowledge of the landscape, and thus better understand the potential epidemiological pathways. The approach of photo-interpretation of satellite images and field confirmation has allowed to consolidate the existing incomplete database. We will also show how risk-based surveillance can guide sampling. In the context of HLB surveillance in Reunion, a list of the most connected orchards was used to target sampling of areas most likely to be epidemiological nodes. We were able to show through learning algorithms that elevation and connectivity are variables of major importance in explaining the health status of citrus. Furthermore, the involvement of home gardens in the epidemic was highlighted, supporting the fact that the surveillance of the agricultural compartment alone was not sufficient. An evaluation of the surveillance system was also carried out using the OASIS method. This allowed us to highlight the good functioning of the core of the surveillance chain, despite the fact that positions in the central organization need to be defined and communication with the general public needs to be improved
Boquel, Sébastien. « Propension vectorielle des pucerons dans l’épidémiologie du virus Y (PVY) en culture de pommes de terre ». Amiens, 2011. http://www.theses.fr/2011AMIE0107.
Texte intégralPotato virus Y (PVY) is a phytovirus transmitted in a non-persistent fashion by aphid vectors to a broad range of plants. A diagnosis carried out in 2006 in Picardy showed that 80 to 90 % of aphids trapped in potato fields corresponded to non-colonizing potato aphids. Thus, the main aim of this thesis was to evaluate the ability of different aphid species to transmit PVY to potato plants, whether they were potato colonizing aphids (Myzus persicae and Macrosiphum euphorbiae) or not (Aphis fabae, Brevicoryne brassicae, Sitobion avenae, Acyrtosiphon pisum et Rhopalosiphum padi). For each aphid species, vector activity, corresponding to the behavioural component (feeding and locomotion behaviour) involved in the spreading of phytoviruses and vector efficiency, corresponding to its ability to acquire and inoculate viruses, were determined. The vector activity study showed that in potato colonizing aphids, apterous individuals, born from colonizing alates, exhibit a sedentary behaviour and that alate dispersal ability is higher in M. Persicae than in M. Euphorbiae. Both colonizing species did not realize interplant movements contrary to non-colonizing ones. Through the electrical penetration graph (EPG) technique, the feeding behaviour study revealed that all species performed the intracellular punctures necessary for virus acquisition and inoculation. The infection status of the plant can modulate aphid vector activity and therefore can strongly impact on the PVY spreading. PVY-infected plants induced a phagostimulant effect on M. Persicae and S. Avenae, and a deterrent one in M. Euphorbiae, A. Fabae and B. Brassicae. Furthermore, dual choice bioassays revealed that all the aphid species tested were unable to discriminate between a healthy and a PVY-infected plant. The vector efficiency study was set up according to a novel methodology that involved the use of in vitro plants and the determination of different virus acquisition periods depending on the aphid species considered. Results showed high transmission rates for potato colonizing aphids (83 % for M. Persicae and 27 % for M. Euphorbiae), a medium to low rate for A. Pisum, B. Brassicae and S. Avenae (< 20 %) and no transmission for A. Fabae and R. Padi. Despite the high transmission rates observed for colonizing aphid species, their involvement in PVY epidemiology may be overestimated due to their sedentary behaviour. By contrast, some non-colonizing species, notably A. Pisum, B. Brassicae and S. Avenae, exhibited a vector activity favouring the spread of viruses and their high population densities in potato fields may compensate for their lower vector efficiency. This work highlights the potential role of non-colonizing potato aphid species and brings new insights into our understanding of the mechanisms governing the PVY epidemiological dynamics
Clérivet, Alain. « Interactions hôte-parasite (Stemphylium floridanum, Hannon et Weber - Solanum gilo, Raddli) ; aspects symptomatologiques, ultrastructuraux et biochimiques ». Montpellier 2, 1990. http://www.theses.fr/1990MON20202.
Texte intégralDuret, Marie-Pierre. « Les modèles en phytopathologie : étude du champignon Sclerotinia sclerotiorum sur colza (Brassica napus) ». Lyon 1, 1992. http://www.theses.fr/1992LYO10120.
Texte intégralSoubeyrand, Samuel. « Spécifier un processus caché non modélisé en déterminant le lien asymptotique entre résidus et processus caché : application à l'analyse de la variabilité dans les expériences de propagation des rouilles du blé ». Montpellier 2, 2005. http://www.theses.fr/2005MON20075.
Texte intégralSanssené, Jean. « Nécroses racinaires du pois causées par Fusarium solani (Mart. ) Sacc. F. Sp. Pisi (Jones) Snyd. & ; Hans. (Nectria haematococca Berk. & ; Br. , Mating Population VI) : connaissance de la maladie et diversité de la population pathogène ». Littoral, 2002. http://www.theses.fr/2002DUNK0092.
Texte intégralFusarium solani f. Sp. Pisi is the most frequent root rot pathogen of peas in France. Before starting a breeding program of resistant varieties, investigation was carried out in two areas. The first one concerns the global study of the disease, with experiments conducted in the field and in semi-sterile conditions in the laboratory. The pathogen affects the plant when the temperature exceeds 8°C, even more in dry conditions. The necrosis is generally centred around the zone of insertion of cotyledons. On the other hand, in dry conditions, it extends superficially over the whole length of the root, while the seed and the epicotyl remain healthy. The plant growth is reduced when the fungus reaches the central cylinder, and induces the degradation of the cambium and the phloem, then prevents the extension of the xylem. The seriousness of the attack is well represented by the notation of rotted section. Secondly, we study the diversity of the French population of solani f. Sp. Pisi, from a collection of hundred monosopore isolates. The sequences and the PCR-RFLP analyses of the ITSs, and of the 28S rDNA, confirm the membership in the mating population MPVI. In this population, different clones were identified by combining the analysis of the esterases and the telomeric extremity. Some of them present common morphological characters useful for their identification. Within a clone, the pathogenicity varies strongly between isolates. Thirty genotypes of pea showed differences of resistance to various clones. As a consequence, the choice of the most frequent clone in France is imperative for the future breeding of resistant pea varieties. This work opens up perspectives of study of the constituents of pathogenicity of F. Solani f. Sp. Pisi, as well as constituents of pea resistance to this pathogen
El, Chartouni Léa. « Conditions françaises de l'intéraction entre Mycosphaerella graminicola, agent de la septoriose du blé, et le blé : diversité et structure d'une population du champignon et modalités de la résistance et de la tolérance chez le blé ». Littoral, 2009. http://www.theses.fr/2009DUNK0249.
Texte intégralWe studied the interaction wheat-M. Graminicola in the French conditions. At first, we looked at the diversity and the structure of M. Graminicola French populations. 364 strains collected from 17 counties were investigated using 4 microsatellite markers (ST1A4, ST1E3, ST1E7 et ST1D7) and 2 actin and β-tubuline partial sequences analyzed with PCR-SSCP. The obtained results confirmed the fungus high adaptation potential in France. We revealed a moderate genetic differentiation with a low gene flow. The population was found to be more structured than previously investigated ones, with 3 groups corresponding to 2 major clusters and a zone of admixture. We then looked at this interaction at cytological and biochemical level. We investigated 5 French wheat cultivars presenting different resistance (R) and tolerance (T) profiles towards M. Graminicola. We noticed that R was linked to rare papillae formation, susceptibility (S) was characterized by intercellular mycelial growth, whereas T presented no impact on the fungal infection process. Lipoxygenase (LOX), peroxidase (PO), and glutathione-S-transferase (GST) activities did not discriminate between R and T profiles. Correlations between cytological and biochemical data with the different R and T profiles revealed that necrosis correlates with LOX in NT cultivars, mycelia surrounding of stomata correlates with PO in R cultivars and direct penetrations correlates with GST in S cultivars. Moreover, we discriminated between S cultivars according to their T profile
As-Sadi, Falah. « Genetic and genomic based approaches towards a better sustainability of sunflower Helianthus annuus resistance to downy mildew Plasmopara halstedii ». Toulouse 3, 2011. http://thesesups.ups-tlse.fr/1534/.
Texte intégralDowny mildew, caused by P. Halstedii, is one of the major diseases for sunflower (Helianthus annuus). Pl genes conferring full, qualitative resistance were discovered and extensively spread in cultivars. They appeared as race-specific and were progressively overcome due to the selection pressure on the pathogen. Thus since 10 years we are witnessing an increase of P. Halstedii races in the fields. Quantitative resistance was found by Tourvieille et al. (2008) and proposed as a solution to counter the rapid evolution of the pathogen. Two QTLs were detected at LG10 and LG8 in a RIL population from XRQ*PSC8 by Vear et al. (2008). With the aim to improve the sustainability of sunflower resistance in gathering knowledge on several aspects of the plant*pathogen interaction, the objectives of this thesis are (i) on the pathogen side, to better characterize P. Halstedii at the genetic and genomic level, (ii) on the plant side, to obtain a fine mapping of the main QTL located on LG10 (QRM1) and (iii) to compare the Pl5 gene and QRM1-R dependent genetic pathways by transcriptomic analysis. The first high-throughput sequencing was performed on infected sunflower which increased the available genomic resources of P. Halstedii and highlighted first putative effectors RXLR and CRN of P. Halstedii. On the plant side, we performed a fine mapping of QRM1: a new BAC library was built and screened to set up a preliminary physical map of the QRM1 region; genetic map of LG10 was enriched with BAC derived markers and a phenotyping method to mimic the quantitative resistance in controlled environment was validated and used to phenotype newly constructed RILs. The QRM1 region was restricted to 1. 5 cM. Using Sunflower Affymetrix chip, transcriptomic analysis revealed different genetic pathways depending on incompatible interaction (Pl5 gene * race 710) or quantitative interaction managed by QRM1-R
Abdelghafour, Florent. « Potentialités de l’imagerie couleur embarquée pour la détection et la cartographie des maladies fongiques de la vigne ». Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0430.
Texte intégralThe downy mildew of the vine is a phytopathology of fungal origin particularly worrying for the wine industry. The aim of this thesis is to study the potentialities of on-board color imaging to estimate the health status of vineyards affected by downy mildew on an intra-plot scale. The proposed solution aims at assisting epidemiological monitoring networks in the estimation of health risks and in the recommendation of chemical control plans. In practice, two image processing chains are proposed, one dedicated to the segmentation of vine organs, and the other to the detection, counting and measurement of symptomatic tissues of downy mildew. These two chains are designed on a common strategy and are aimed at images acquired directly at the plot under the conditions of viticultural work. The proposed strategy is based on structure-color representations and probabilistic models of the tissue classes present in the vines. It operates in three steps : Formulating descriptors to extract the characteristic and discriminating properties of each class ; Modelling the statistical distributions of these descriptors in each class ; Assigning each pixel to on of the classes according to its suitability to their models. The descriptors combine the Local Structure Tensors (LST) with colorimetric statistics calculated in the neighborhood of the pixel considered. To account for the specific nature of LSTs, the descriptors are transformed to be represented in the Log-Euclidean space. In this space, it becomes possible to model the classes of interest by distributions of multivariate Gaussian mixtures of structure-color representations. This strategy is first applied to healthy vine images. It involves the partitioning of an image into organ classes (foliage, bunches or inflorescences and stems). A pixel-wise MAP (Maximum A Posteriori) classification is carried out and regularized by stochastic relaxation and mathematical morphology operations. The results obtained for three phenological stages are very convincing. In addition, the processing chain is robust to the setting of the main hyperparameters. In a second step, the previous methodological chain is adapted to process images with symptoms of downy mildew as well as necrosis, discolorations, deficiencies, mechanical wounds, which are confounding factors. The decision method is based on a reconstruction of symptoms by propagation around germs. The criteria used are based on the previously defined color-structure representations and probabilistic models. The new processing chain reliably detects downy mildew symptoms and estimates the area of the affected tissues
Barnouin, Jacques. « Approche écopathologique de la composante nutritionnelle des troubles de santé chez la vache laitière : des facteurs de risque aux mécanismes de la pathogénicité ». Montpellier 2, 1992. http://www.theses.fr/1992MON20095.
Texte intégralCrete, Rémi. « Prise en compte de l'hétérogénéité spatiale dans la modélisation de la dynamique du développement de la tavelure du pommier ». Angers, 2013. http://www.theses.fr/2013ANGE0060.
Texte intégralApple scab is one of the major diseases in apple orchards. Caused by an ascomycete fungus called venturia inaequalis, it can serious consequences for fruit production. The objective of this work is to model the spatiotemporal spread of scab, using data from an experiment conducted between 2004 and 2008 in an orchard located at INRA of Angers. Our model is based on a spatiotemporal poisson point process whose intensity represents the risk of infection by the pathogen. This intensity takes into account the main components of development of the disease : spore production, dispersal and infection in two main phases of contamination, as well as some environmental and climatic factors. In the introduction, we present the context and issues related to scab, we describe the experiment results and we provide some descriptive data analysis. After an overview of mathematical models used in plant epidemiology we define our model, spatially discrete and continuous in time. It depends on a few unknown parameters describing the various components of the development of the disease. Finally, we propose a method for parameter estimation based on a Bayesian approach, some numerical results from MCMC algorithm implemented and give conclusions on the spatial spread of scab
Vidal, Tiphaine. « Intérêt de la diversité architecturale des plantes cultivées pour limiter la progression épidémique de maladies foliaires à dispersion pluviale : cas de la septoriose au sein d'associations variétales de blé ». Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLA012/document.
Texte intégralGrowing mixtures of susceptible and resistant cultivars in the same field makes it possible to reduce the propagation of airborne fungal plant diseases. Plant architecture has an impact on spore dispersal or microclimate, but is rarely taken into account in mixture design. The objective of this work was to understand the role of canopy architecture in mixtures of cultivar of different levels of resistance to a disease dispersed by rain-splash, septoria tritici blotch, caused by Zymoseptoria tritici. A controlled conditions experiment made it possible to quantify relationships between spore interception and canopy architecture. Differences of canopy density between pure stands and mixtures led to a reduction in disease on susceptible plants grown in mixture, compared to the susceptible pure stand. During a field experiment, mixtures of cultivars with contrasted stem height were less diseased than those with similar stem height. These results were related to the effect of canopy architecture on spore dispersal and leaf wetness duration. A spatially explicit modeling approach made it possible to identify splash dispersal mechanisms related to the architecture of mixed canopies. In mixtures of cultivar with diverse plant height, the amount of splashed inoculum depended on leaf area located above diseased leaves (umbrella effect). The amount of inoculum intercepted by a leaf layer was related to its difference of height between the inoculum sources (height effect). Differences of plant height between cultivars composinga mixture modulated the interception of spores by resistant leaves, providing an increased protection of susceptible leaves (barrier effect). Our results suggest that considering cultivar architecture in the design of cultivar mixtures could make it possible to improve the management of splash-dispersed diseases
Soewarto, Julia. « Maladie fongique et profils de vulnérabilité : le cas de la rouille des Myrtaceae (Austropuccinia psidii) en Nouvelle-Calédonie ». Thesis, Nouvelle Calédonie, 2017. http://portail-documentaire.unc.nc/files/public/bu/theses_unc/Manuscrit-these-corrige-SOEWARTO.pdf.
Texte intégralInvasive alien species and emerging infectious diseases represent a growing worldwide problem and constitute one of the major threats to biodiversity. New Caledonia, an archipelago located in the South West Pacific, is recognized as one of the major biodiversity hotspot. The native vascular flora illustrates this outstanding biological uniqueness, with 3250 species of which over 74 % are endemic. In this context, management and preservation of this biodiversity is a priority issue.Austropuccinia psidii is a fungus considered to be one of the major environmental threats to plants belonging to the family Myrtaceae on a global scale. Commonly known as "Myrtle rust", this pathogen has been observed in New Caledonia in 2013. The establishment of this exotic plant pathogen is of concern given the environmental importance of Myrtaceae in the archipelago ecosystems of Myrtaceae.The objective of this thesis is to put in place a strategy to control both the expansion of the pathogen in a natural environment and in nurseries cultivating Myrtaceae.In a first part, we will highlight the importance of the impact of A. psidii in terms of geographic extent, host range and severity of symptoms. This information is essential to specifically target the conservation priorities of the species most affected and preserved their habitats. The results show that A. psidii impacts a wide range of Myrtaceae species on the territory. Variations in the severity of the symptoms expressed between individuals of the same species suggest the possibility of initiating integrated control strategy based on the selection of traits related to resistance to this disease.In a second part, we will try to identify genetic markers to discriminate individuals according to the phenotype of resistance they express to the infection caused by myrtle rust. By using an RNA-Seq approach, combining both differential gene expression and the search for nucleotide variations positioned in coding parts of the genomes, we were able to identify discriminant candidate genes for resistant vs susceptible in endemic Myrtaceae species known for their patrimonial, economic or ecological role. Among these candidate genes some admit known functions involved in mechanisms of resistance to pathogens
Nilusmas, Samuel. « Gestion durable des nématodes à galles en culture maraîchère par la modélisation et l’optimisation du déploiement de variétés résistantes ». Thesis, Université Côte d'Azur, 2020. http://www.theses.fr/2020COAZ4086.
Texte intégralRoot-knot nematodes are obligate soil-borne endoparasites of plant roots that cause major yield losses throughout the world. Environmentally-friendly plant protection methods against root-knot nematodes are mainly based on the use of resistant plant cultivars. These cultivars efficiently control nematode populations naturally present in the field, but they favour the emergence of virulent variants that circumvent the resistance genes carried by these cultivars. Since virulence is associated with fitness costs, which limit the virulent nematode ability to infest plant roots or reproduce, susceptible crops counter-select virulent nematodes. The aim of this thesis is to identify effective and sustainable resistance deployment strategies to control root-knot nematodes in horticultural crops. To this end, we developed a semi-discrete epidemiological model describing the nematode dynamics in the soil and in the roots of a resistant or susceptible plant during its growing season, as well as the survival of nematodes in the soil between cropping seasons. The model was fitted to experimental data of within-season infestation of susceptible tomato roots. It was used to determine the rotation strategies alternating susceptible and resistant plants that maximise an average yield proxy, over different time horizons and for different combinations of epidemiological intensity and genetic parameters (mutation rate and virulence costs). Moreover, sensitivity analyses were performed to assess the robustness of the plant resistance deployment strategies. Our results show that carefully designed rotation strategies would not only increase crop yield, but also preserve the sustainability of resistance genes. Sensitivity analyses were performed to evaluate the robustness of our results. This thesis opens both experimental and modelling perspectives for a better control of root-knot nematodes
Aguayo, Silva Jaime Cristián. « Étude des conditions de l'émergence du phytophthora alni sur l'aulne glutineux ». Thesis, Université de Lorraine, 2012. http://www.theses.fr/2012LORR0153/document.
Texte intégralSince the early 1990's alder decline caused by the oomycete Phytophthora alni subsp. alni (Paa) is one of the most important threats to riparian ecosystems in Europe. The emergence of Paa is related to an interspecific hybridization event between two related species -initially considered as Paa variants- misnamed as Phytophthora alni subsp. uniformis (Pau) and Phytophthora alni subsp. multiformis (Pam). The objective of this thesis was to identify the factors that may have contributed to the emergence of the disease in Europe. Following a population genetics approach we showed that Pau is likely to be an invasive species in Europe, probably native to North America. Its introduction would have enabled hybridization with Pam and, consequently be a major cause on the emergence of Paa. Our results confirm that Paa has arisen from several hybridization events, which have geographically structured its European populations. Paa's genetic variability, revealed by microsatellite markers, showed low levels of polymorphism, with a dominant genotype scattered throughout Europe. In addition, a modelling approach revealed that alders' crown decline is linked to temperature. In particular, the disease incidence increases during mild winters which favours mycelium survival as Paa does not produce resistant spores (chlamydospores or oospores). The effect of summer temperatures is more complex to explain. Disease incidence decreases when summer temperatures are higher, but this phenomenon can also be linked to the physiological conditions of trees or changes in soil microbiological communities. Conversely, tree recovery is favoured by lower winter and higher summer temperatures. Climate change does not explain the emergence of the disease. However, increases in winter temperatures du to climate change may strengthen the epidemic
Papaïx, Julien. « Structure du paysage agricole et risque épidémique, une approche démo-génétique ». Thesis, Paris, AgroParisTech, 2011. http://www.theses.fr/2011AGPT0056/document.
Texte intégralAgriculture intensification has improved food production impressively in the past 50 years but this came with an increasing impact on the environment. In particular, modern agriculture has led to the simplification of the environmental structure over vast areas. As a consequence, agro-ecosystems are particularly susceptible to epidemics. The increase of crop genetic diversity is a promising way for reducing the risk of occurrence and development of diseases in crops but the technical and organisational conditions required to manage the genetic resources at this scale have not been established yet. This will require shifting the scale of crop protection investigations from the field to the agricultural landscape. In this PhD thesis we focus on landscape-scale processes and on the potential role of functional diversity in cultivated landscapes to better control plant diseases. We identified three questions: how does a pathogen population spread over a heterogeneous host landscape? How do pathogen genotypes compete in a diversified host population? And, in a longer term, how do pathogen populations evolve in response to host landscape structure? Each of these questions is investigated through the analysis of real data and the development of theoretical approaches. We demonstrate that the composition and the spatial structure of the host landscape greatly influence the pathogen population dynamics and evolution. The recommendations that this work could provide in order to practically manage the genetic resources will depend on the desired aim and will request further collaborative work withthe professional operators
Pages, Marielle. « Effets et mécanismes d'action de l'ozone utilisé comme moyen de lutte contre des champignons pathogènes du pommier : études in vitro et in vivo ». Thesis, Toulouse, INPT, 2015. http://www.theses.fr/2015INPT0102.
Texte intégralApple trees are the target of a lot of pests and fungal diseases, responsible for many economic losses. Farmers treat these micro-organisms mainly with pesticides. Plant-protection products are today very controversial. French and European authorities control their use by means of numerous regulations. Therefore, an alternative solution with a low remanence must be found in order to limit fungal diseases. The aim of this thesis is to evaluate the innovative process efficiency based on the use of ozonated water against four fungal species: Venturia inaequalis, Botrytis cinerea, Neofabraea alba and Phytophthora syringae. Firstly, this work of thesis verified the ozone antifungal action on spores suspensions of the four fungal species and on different stages of development of V.inaequalis spores. According to the species and stages of development considered, a difference of sensibility was detected. Moreover, alteration of the membrane, due to ozone action, was observed thanks to several experimentations: quantification of phospholipids peroxidation, spore observations with Scanning Electron Microscopy and with Optical Microscopy after staining. Secondly, the ozonated water effects on seedlings previously contaminated by V.inaequalis spores were evaluated. This study confirmed the anti-fungal action of water containing ozone. It was also observed the importance of the water and of ozone quantities supplied. These quantities must be controlled to optimize the antifungal action of the treatment. These results validated the ozone application as a fungicide alternative of use of pesticides. Additional researches will be made concerning the treatment modalities: the aim is to transfer the technology from the laboratory to the orchard
Pasquier, Grégory. « Etude de l’impact de l’Esca sur la qualité des raisins par une approche protéomique ». Thesis, Bordeaux 2, 2012. http://www.theses.fr/2012BOR21909/document.
Texte intégralThe 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