Paraburkholderia phytofirmans souche PsJN est une bactérie endophyte capable d’induire une promotion de croissance de la vigne et de lui conférer une tolérance vis-à-vis des basses températures. Puisque la bactérie PsJN induit également une tolérance de la vigne contre la pourriture grise causée par le champignon Botrytis cinerea, l’objectif de ce travail était de caractériser les mécanismes de la résistance induite par P. phytofirmans suite à une infection par B. cinerea chez la vigne.Nos résultats indiquent que l’inoculation des racines de vitroplants par la bactérie PsJN entraîne des modifications du métabolisme phénolique au niveau des plantules bactérisées. En effet, des tanins d’origine gallique et ellagique sont accumulés au niveau des racines en réponse à PsJN alors qu’une accumulation de lignine a été observée dans la tige et d’anthocyanes dans les feuilles. De même, PsJN induit une résistance contre B. cinerea en potentialisant l'expression de gènes de défense dépendants de l’acide salicylique et de l’acide jasmonique dans les feuilles de vigne. Parallèlement, une accumulation de callose et d’H2O2 a été observée ainsi qu’une meilleure mobilisation des glucides dans les plantules bactérisées, corrélée à une réduction des dommages de l’activité photosynthétique.Suite aux résultats obtenus avec le modèle vitroplant, nous avons optimisé la bactérisation des boutures fructifère et évaluer l’impact de cette bactérie sur la résistance des inflorescences contre B. cinerea. Les résultats présentés dans ce travail permettent d’envisager l’utilisation de la bactérie PsJN comme agent de lutte biologique. / Paraburkholderia phytofirmans strain PsJN is an endophytic beneficial bacterium able to promote the growth of grapevine and to induce the plant resistance to biotic and abiotic stresses. Indeed, the interaction between PsJN and grapevine confers to the grapevine a protection towards cold stress (4 °C), by reducing damages on the photosynthetic system and modulating the carbon metabolism. The PsJN strain also induces a protection against gray mold caused by Botrytis cinerea. In this context, the aim of this work was to better characterize this P. phytofirmans strain PsJN-induced resistance in grapevine against B. cinerea.Our results indicate that the inoculation of in vitro-plantlets roots with PsJN altered the phenolic metabolism in bacterized-plantlets. Gallic and ellagic derived tannins are clearly accumulated in roots of bacterized-plantlets whereas an accumulation of lignin in stems and anthocyanins in leaves was observed. We also showed that PsJN induces a protection against B. cinerea by priming the expression of genes involved in salicylic acid and jasmonic acid pathways. In parallel, an accumulation of callose and H2O2, as well as a better mobilization of carbohydrates in bacterized plantlets were observed. In addition to the defense mechanisms setting up by plants, we demonstrated that PsJN reduces in vitro and in vivo development of B. cinerea, in a dose-dependent manner.Following results obtained with the in vitro-plantlets model, we optimized the protocol of bacterization of grapevine fruiting cuttings by the PsJN strain, and evaluate the impact of the bacteria on to induce the resistance of inflorescences to B. cinerea. Our results provide new insights for the use of PsJN and suggest its commercial use as a biological control agent.

Il est actuellement estimé qu’environ 13% du vignoble français est improductif suite aux pathologies affectant le bois des ceps, la principale d’entre elles étant l’esca. Parmi les moyens de lutte mis en œuvre, le biocontrôle, via l’utilisation d’un oomycète, Pythium oligandrum, est actuellement développé pour protéger les plants de vigne contre un agent pathogène pionnier de l’esca, Phaeomoniella chlamydospora. La sélection de souches de P. oligandrum, isolées du vignoble, et produisant in vitro des quantités importantes d’une protéine élicitrice, l’oligandrine, des systèmes de défense des végétaux a d’abord été réalisée. Trois essais en serre ont montré qu’une réduction significative (40 à 50%) des nécroses dues P. chlamydospora était observée après application d’inocula de l’oomycète sur les racines des plants de vigne pied-francs Au niveau de la tige, le niveau d’expression de 22 gènes impliqués dans les mécanismes de défenses de Vitis vinifera a été mesuré par PCR quantitative et des réponses spécifiques du végétal ont été observées selon les traitements. Six gènes (protéines PR, voie des phenylpropanoïdes, oxylipines et le système d’oxydo-réduction) ont été fortement induits lorsque les plants ont été pré-inoculés par P. oligandrum puis infectés par P. chlamydospora. Afin de mettre en évidence les mécanismes spécifiques mis en place lors de cette interaction tripartite, l'analyse de la réponse transcriptomique globale de la vigne (par microarray et RNAseq), au niveau de la tige, a été réalisée chez ces plants qui manifestent une résistance induite systémique (ISR). Plusieurs gènes impliqués dans la synthèse de l’éthylène et des jasmonates sont fortement induits, chez les plants pré-traités par l’oomycète puis infectés par l’agent pathogène. Plusieurs facteurs de transcription régulant ces voies de signalisation sont également fortement induits. Suite à l’analyse des populations de messagers (mRNA) de P. chlamydospora, il a été observé que les niveaux d’expression de gènes impliqués dans la synthèse des métabolites secondaires, des facteurs de transcription impliquées dans la régulation de différentes voies chez les champignons et certaines Carbohydrates Actives enZymes étaient modulés en présence de P. oligandrum au niveau racinaire. Ces résultats montrent que la colonisation du végétal par l’oomycète, même à distance de P. chlamydospora, induit un stress indirect important chez celui-ci. Afin d’optimiser l’implantation de cet agent de biocontrôle en pépinière et au vignoble, l’aptitude de P. oligandrum à coloniser les racines de plants de vignes greffés et à les protéger contre P. chlamydospora a été étudiée. Trois portes-greffes (SO4, 3309 et 101-14) greffés sur des cépages (Cabernet Sauvignon et Sauvignon Blanc) ont été inoculés ou non par P. oligandrum. L’oomycète s’implantait sur les différents systèmes racinaires, mais en proportion variable selon les associations cépage/porte-greffe utilisées. Les analyses par empreintes moléculaires (Single Strand Conformation Polymorphism) ont montré que des microflores fongiques et bactériennes complexes et diversifiées colonisaient les feuilles et les racines, mais que l’introduction de P. oligandrum sur la plante n’induisait pas de bouleversements directs ou indirects notables au niveau de ces microflores indigènes. Une protection des jeunes plants de vigne greffés (SO4 + Cabernet Sauvignon) semble être induite par P. oligandrum contre l’agent pathogène, P. chlamydospora. / Approximately 13% of French vineyards are currently considered unproductive due to trunk diseases, mainly Esca, a particularly destructive disease that affects grapevines worldwide. Accordingly, biological control of a pathogen implicated in Esca, Phaeomoniella chlamydospora, was developed using the oomycete, Pythium oligandrum. The selection of P. oligandrum strains, isolated from vineyards, which produced in vitro large quantities of oligandrin, an elicitin-like protein inducing plant defences, was carried out. Three greenhouse assays showed that the necroses caused by P. chlamydospora were significantly reduced (40 to 50%) when P. oligandrum colonized the root system of vine cuttings. At stem level, the expression of a set of 22 genes involved in Vitis vinifera defence mechanisms was measured by quantitative PCR. Depending on the treatments employed, significant differences in grapevine responses were observed. Six of the genes (PR proteins, phenyl-propanoid pathway, oxylipins and the oxydo-reduction system) were strongly induced in plants pre-treated with P. oligandrum, and subsequently infected by P. chlamydospora. In order to characterize the mechanisms occurring during this tri-partite interaction, the global transcriptomic grapevine responses at stem level were analysed, using microarray and RNAseq, in plants in which induced systemic resistance (ISR) had taken place. Several genes involved in ethylene and jasmonate biosynthesis were strongly induced in plants that were pre-treated with P. oligandrum, and subsequently infected by P. chlamydospora. The transcription factors involved in the regulation of these signalisation pathways were also induced. Analysis of the P. chlamydospora RNA messenger (mRNA), showed that certain genes involved in secondary metabolite synthesis, transcription factors implicated in pathway regulations, and certain Carbohydrate Active enZymes, were modulated, when P. oligandrum colonised the roots. These results demonstrated that root inoculation with P. oligandrum induced indirect stress on P. chlamydospora responses. In order to promote P. oligandrum implantation in nurseries and vineyards, the capacity of this biocontrol agent to colonize the roots of grafted-plants, and to protect them against P. chlamydospora attacks, was studied. Three rootstocks (SO4, 3309 and 101-14), grafted on two scion varieties (Cabernet Sauvignon and Sauvignon Blanc), were inoculated or not with P. oligandrum. Depending on the particular scion/rootstock associations, the oomycete colonized the various root systems differently. Single Strand Conformation Polymorphism (SSCP) analyses revealed complex and diverse fungal and bacterial communities in both the rhizosphere and the phyllosphere. These microflora, which were organ-dependent, were not direcly or indirectly affected by the root inoculation of P. oligandrum. Protection of grafted vines (SO4 + Cabernet Sauvignon) was probably induced by P. oligandrum against the pathogen, P. chlamydospora.

L'esca de la vigne fait partie des maladies de dépérissement incurables dont l'étiologie n'est pas complément élucidée. Elle représente un des problèmes majeurs en viticulture. L'objectif général de cette thèse est d'améliorer la compréhension des processus épidémiques et des facteurs de risque. Pour ce faire, nous avons mené une étude quantitative du développement spatio-temporel de l'esca à l'échelle de la parcelle. Dans un premier temps, pour détecter d'éventuelles corrélations spatiales entre les cas de maladie, des tests statistiques non paramétriques sont appliqués aux données spatio-temporelles d'expression foliaires de l'esca pour 15 parcelles du bordelais. Une diversité de profils spatiaux, allant d'une distribution aléatoire à fortement structurée est trouvée. Dans le cas de structures très agrégées, les tests n'ont pas montré d'augmentation significative de la taille des foyers, ni de propagation secondaire locale à partir de ceps symptomatiques, suggérant un effet de l'environnement dans l'explication de cette agrégation. Dans le but de modéliser l'occurrence des symptômes foliaires, nous avons développé des modèles logistiques hiérarchiques intégrant à la fois des covariables exogènes liées à l'environnement et des covariables de voisinage de ceps déjà malades mais aussi un processus latent pour l'auto-corrélation spatio-temporelle. Les inférences bayésiennes sont réalisées en utilisant la méthode INLA (Inverse Nested Laplace Approximation). Les résultats permettent de conforter l'hypothèse du rôle significatif des facteurs environnementaux dans l'augmentation du risque d'occurrence des symptômes. L'effet de propagation de l'esca à petite échelle à partir de ceps déjà atteints situés sur le rang ou hors rang n'est pas montré. Un modèle autologistique de régression, deux fois centré, qui prend en compte de façon plus explicite la structure spatio-temporelle de voisinage, est également développé. Enfin, une méthode géostatistique d'interpolation de données de nature anisotropique atypique est proposée. Elle permet d'interpoler la variable auxiliaire de résistivité électrique du sol pour estimer à l'échelle de chaque plante de la parcelle, la réserve en eau du sol disponible pour la vigne. Les méthodes géostatistique et spatio-temporelles développées dans cette thèse ouvrent des perspectives pour identifier les facteurs de risques et prédire le développement de l'esca de la vigne dans des contextes agronomiques variés. / Esca grapevine disease is one of the incurable dieback disease with the etiology not completely elucidated. It represents one of the major threats for viticulture around the world. To better understand the underlying process of esca spread and the risk factors of this disease, we carried out quantitative analyses of the spatio-temporal development of esca at vineyard scale. In order to detect the spatial correlation among the diseased vines, the non-parametric statistical tests were applied to the spatio-temporal data of esca foliar symptom expression for 15 vineyards in Bordeaux region. Among vineyards, a large range of spatial patterns, from random to strongly structured, were found. In the vineyards with strongly aggregated patterns, no significant increase in the size of cluster and local spread from symptomatic vines was shown, suggesting an effect of the environment in the explanation of this aggregation. To model the foliar symptom occurrence, we developed hierarchical logistic regression models by integrating exogenous covariates, covariates of neighboring symptomatic vines already diseased, and also a latent process with spatio-temporal auto-correlation. The Bayesian inferences of these models were performed by INLA (Inverse Nested Laplace Approximation) approach. The results confirmed the effect of environmental factors on the occurrence risk of esca symptom. The secondary locally spread of esca from symptomatic vines located on the same row or out of row was not shown. A two-step centered auto-logistic regression model, which explicitly integrated the spatio-temporal neighboring structure, was also developed. At last, a geostatistical method was proposed to interpolate data with a particular anisotropic structure. It allowed interpolating the ancillary variable, electrical resistivity of soil, which were used to estimate the available soil water content at vine-scale. These geostatistical methods and spatio-temporal statistical methods developed in this thesis offered outlook to identify risk factors, and thereafter to predict the development of esca grapevine disease in different agronomical contexts.

Les maladies du bois de la vigne (MDBs) et plus particulièrement l’esca, sont devenues en l’espace de deux décennies l’objet de préoccupations majeures puisqu’elles mettent en danger la pérennité de nombreux vignobles partout dans le monde. En Tunisie, ces maladies sont peu connues mais elles semblent être en pleine expansion et, en France, environ 13% du vignoble est improductif à cause des dépérissements qu’elles provoquent. Pour lutter contre les MDBs, les filières viticoles françaises et tunisiennes sont actuellement dans une impasse technique car elles ne disposent d’aucune méthode de lutte chimique « curative ». Dans ce contexte, l’objectif de cette thèse est de (i) déterminer quels agents pathogènes sont responsables des dégradations du bois de la vigne en Tunisie ? Les symptômes correspondent-ils à ceux de l’esca ? Existe-t-il une spécificité des agents pathogènes chez les ceps tunisiens ? Aussi (ii) afin de lutter contre ces maladies du bois (MDBs), de potentiels agents de biocontrôle bactériens ont été recherchés dans les parties ligneuses de ceps sélectionnés dans des vignobles tunisiens. Ils ont été caractérisés et des essais de protection in planta ont été réalisés. [...] Ces champignons ont été identifiés au niveau morphologique et moléculaire. Leur pathogénicité a été confirmée après inoculation sur jeunes plants de vigne. Des travaux originaux basés sur la co-inoculation de plants de vigne par ces 3 pathogènes ont montré qu’ils pouvaient rentrer en compétition entre eux au sein du végétal. Par ailleurs, sur le même thème, 2 autres pathogènes des MDBs, i.e. Phomopsis viticola et Diploidia seriata, ont été isolés dans une autre étude à partir de ceps prélevés dans la même région en Tunisie. Dans une deuxième étape, la microflore bactérienne colonisant les tissus ligneux de vignes prélevées dans le nord de la Tunisie a été étudiée afin de rechercher des agents de lutte biologique potentiels. La technique d’empreinte moléculaire Single-Strand Conformation Polymorphism (SSCP) a d’abord montré que les communautés bactériennes étaient différentes en fonction des tissus qu’elles colonisaient, i.e. le bois nécrosé ou sain. Soixante-neuf souches bactériennes ont été isolées par méthode pasteurienne, et les 19 souches les plus abondantes ont fait la suite de l’étude. L’identification moléculaire de ces souches par séquençage de l’ARNr 16S et du gène rpoB a montré l’existence de 4 genres colonisant les ceps de vignes : Bacillus, Curtobacterium, Pantoea et Pseudomonas. Ces bactéries ont été également caractérisées au niveau biochimique, métabolique et génétique. Des tests de sélection in vitro contre les trois pathogènes fongiques ont été effectués, suite auxquels, une souche B6 de B. subtilis a été sélectionnée pour des essais de protection in planta en serre. Par la suite, une étude combinant deux bactéries antagonistes isolées de bois de vigne tunisien, i.e. B. subtilis B6, et français, i.e. Pantoea agglomerans S5, a été réalisée pour lutter contre 2 agents pathogènes, Phaeomoniella chlamydospora (isolé des vignobles français) et N. parvum (isolé des vignobles tunisiens), impliqués dans les MDBs. Deux cépages, un fréquent en Tunisie, le Muscat d’Italie, et l’autre en France, le Cabernet Sauvignon, ont été utilisés. En effet, suivant l’agent pathogène et le cépage utilisés, les résultats de protection obtenus étaient différents. Les meilleurs résultats de protection ont été obtenus en combinant les bactéries et en les appliquant sur Muscat d’Italie contre les 2 champignons pathogènes. La spécificité et l’efficacité de la protection biologique a ici été démontrée. / Grapevine trunk diseases (GTDs) such as esca are of major concern for viticulture worldwide. In Tunisia, knowledge about the symptoms of this disease and the microflora associated with, is still incomplete despite their ability to cause considerable damage to vineyards. In France, around 13% of whole vineyard is unproductive because of GTDs, and no effective treatment currently exists. In that context, the objectives of the present PhD study were: (i) to characterize the fungal microflora inhabiting the wood tissues of Tunisian esca-foliar symptomatic vines in order to identify the pathogens responsible for wood decay. (ii) To investigate the bacterial microflora colonizing the wood tissues of Tunisian grapevines cv. Muscat d’Italie in order to find a suitable Biological Control Agent (BCA) that can be applied to vineyards. First, in order to better characterize the microflora colonizing the wood tissues of vine, samples were collected from 10 vineyards in the north of Tunisia. Fungal isolates were obtained from trunk of grapevines showing decline, small and distorted leaves and chloroses. To identify the isolated fungal species, sequencing of the Internal Transcribed Spacer region of the rDNA was performed (ITS1 and ITS4 primers). Three pathogens, i.e. Lasidiodiplodia pseudotheobromae, Neofusicoccum parvum and Schizophyllum commune, described in the literature as involved in GTDs were isolated for the first time in Tunisia. Their pathogenicity was confirmed in planta. Moreover, the coinoculation of these 3 fungi in planta, showed that they displayed a competitive inhibition effect on each other. In another study, two others pathogens involved in GTDs, i.e. Phomopsis viticola and Diploidia seriata were also isolated from the same region. This PhD also aimed at identifying the bacterial microflora inhabiting the wood tissues of escafoliar symptomatic vines, i.e. necrotic and non-necrotic wood, using microbiological and molecular approaches. Complex bacterial communities, as shown by Single-Strand Conformation Polymorphism (SSCP) analyses, colonize both types of wood tissues. After isolation, the 19 most abundant cultivable strains were sequenced (16S rRNA and rpoB genes) and identified as belonging to four genera: Bacillus, Pantoea, Pseudomonas and Curtobacterium. They were then screened for their in vitro antagonistic traits against the three pathogenic fungi L. pseudotheobromae, N. parvum and S. commune. Based on the results obtained, two bacterial strains were selected: B. subtilis (strain B6) and Pantoea agglomerans (strain S5), respectively isolated from Tunisian and French grapevines. They were then tested in planta on young vines of cv Muscat d’Italie and Cabernet Sauvignon against two fungal pathogens involved in GTDs, i.e. N. parvum (isolated from Tunisian wood) and Phaeomoniella chlamydospora (isolated from French vines). Young vines of both cultivars were inoculated by B. subtilis B6, P. agglomerans S5 or the combination of B6+S5, singly or in combination with N. parvum and P. chlamydospora. In terms of plant protection, the most efficient condition to reduce in planta necrosis caused by the fungal pathogens in the two cultivars was the combination of the two bacteria. However, bacterial treatments were significantly more efficient to reduce necrosis caused by N. parvum or P. chlamydospora in Muscat d’Italie than in Cabernet Sauvignon.

Le mildiou de la vigne est causé par l’oomycète Plasmopara viticola, qui s’attaque aux parties aériennes non-lignifiées affectant la production viticole. Une alternative à l’utilisation de pesticides est l’utilisation de variétés de vigne à la résistance durable, et un programme pour leur création par croisement entre espèces résistantes et la vigne cultivée, Vitis vinifera, est en cours. Ce programme nécessite l’identification de nouveaux gènes de résistance, ce que le projet vise à faire par (1) le criblage de vignes résistantes avec des effecteurs conservés chez P. viticola, (2) l’étude fonctionnelle d’effecteurs candidats. Le criblage de plantes résistantes n’a conduit à l’identification d’aucun nouveau facteur de résistance majeur. L’étude fonctionnelle d’effecteurs a permis la mise en évidence d’une nouvelle famille d’effecteurs chez P. viticola et a conduit à l’identification de deux effecteurs Pv33, nucléaire, et Pv47, associé au réticulum endoplasmique, qui induisent des défenses végétales. / Grapevine downy mildew is caused by the oomycete Plasmopara viticola, which attacks the aerial non-lignified tissues affecting wine production. An alternative to the use of pesticides is the use of vine varieties with sustainable resistances. A programme aiming to create such varieties by crossing resistant species with the cultivated grapevine, Vitis vinifera, is ongoing. Within this program requiring the indentification of new resistance genes, which the project aims to do by (1) screening resistant vines with effectors stored in P. viticola, (2) performing a functional study of candidate effectors. The screening of resistant plants did not lead to the identification of any new major resistance factors. The functional study of effectors revealed a new family of effectors in P. viticola and led to the identification of two effectors Pv33, nuclear, and Pv47, associated with the endoplasmic reticulum, which induce plant defences.

Erysiphe necator (Schwein.) è l’agente causale dell’oidio della vite. Esso è in grado di svernare come ascospore all’interno di corpi fruttiferi, i chasmoteci, oppure come micelio in gemme infette. Le ascospore sono rilasciate nella primavera successiva e causano infezioni primarie che danno origine all’epidemia. Di conseguenza la riduzione dell’inoculo primario svernante potenzialmente riduce le epidemie nella stagione successiva. I primi sei capitoli di questa tesi riguardano nuove conoscenze sulla biologia, epidemiologia e modellistica del patogeno. Due nuovi modelli meccanicistici che simulano, rispettivamente, la maturazione e dispersione dei chasmoteci e le infezioni ascosporiche sono stati sviluppati ed è stata studiata approfonditamente la dinamica di maturazione e dispersione delle ascospore stesse. Nei restanti quattro capitoli il controllo del patogeno è stato riconsiderato in accordo con le linee guida della gestione integrata del vigneto. In particolare è stata valutata l’efficacia di diversi fungicidi, dell’iperparassita Ampelomyces spp. e di un olio minerale nel ridurre il numero di chasmoteci prodotti in autunno, nel distruggere gli stessi durante l’inverno e nel controllare le infezione primarie ascosporiche in primavera. / Erysiphe necator (Schwein.) is the causal agent of grapevine powdery mildew. It survives the winter in two ways: as ascospores in overwintering fruiting bodies, the chasmothecia, and as mycelium in infected buds. Ascospores that are repeatedly released and cause primary infections in the following grapevine growing season and trigger powdery mildew epidemics. Consequently, the reduction of the overwintering inoculum may reduce powdery mildew epidemics in the next season. In order to verify this statement and develop sanitation as a relevant strategy to be used in integrated management of grape powdery mildew, different studies were performed during this Doctorate. The first six chapters of this dissertation pertain to new findings about the biology, epidemiology and modeling of the pathogen. A new mechanistic model predicting maturation and dispersal of chasmothecia was developed, dynamics of ascospore maturation and dispersal were studied and another mechanistic model simulating ascosporic infections was developed. In the last four chapters the control of the pathogen was redrawn according to the Integrated Pest Management concept: the efficacy of fungicides, the hyperparasite Ampelomyces spp., and mineral oil in reducing chasmothecia production in fall, in killing chasmothecia before bud break, and in controlling ascosporic infections in spring was investigated.

A movement protein Potato virus X (PVX) chimera virus (PVX.GFP(CH3)) bearing the grapevine virus Grapevine rupestris stem pitting-associated virus (GRSPaV) triple gene block proteins (TGB) (denoted P1, P2 and P3) instead of the PVX TGB was delivered into N. benthamiana and other related species by agro-inoculation. This movement protein PVX chimera virus was found to be unable to support the local and systemic movement of PVX in cis. Local and systemic movement of this PVX chimera virus was restored in trans by the dianthovirus Red clover necrotic mosaic virus (RCNMV) movement protein and by a PVX TGB rescue virus that replaced the GRSPaV TGB with the PVX TGB (PVX.GFP(Rescue)). However, a PVX TGB hybrid chimera virus (PVX.GFP(HY2)) containing PVX P1 and the GRSPaV TGB had limited cell-to-cell, but not systemic, movement.

Gli obbiettivi di questa tesi di dottorato erano: i) valutare l’effetto di differenti condizioni ambientali sulla biologia ed epidemiologia di isolati di B. cinerea appartenenti alle sub-popolazioni transposa e vacuma, e ii) sviluppare un nuovo modello previsionale per predire il rischio di muffa grigia nei vigneti tra le fasi fenologiche di sviluppo delle infiorescenze e maturazione dei grappoli. Gli effetti della temperatura, durata di bagnatura e umidità relativa sulle infezioni di infiorescenze e bacche di Vitis vinifera sono stati valutati con inoculazioni artificiali di isolati di B. cinerea. Gli effetti della temperatura, attività dell’acqua, umidità relativa e composizione delle bacche di uva sulla germinazione dei conidi, crescita miceliale e produzione di conidi sono stati valutati su substrati artificiali. I risultati evidenziano che la capacità di causare infezioni varia con gli isolati indipendentemente dall’appartenenza alle sub-popolazioni transposa o vacuma. Inoltre, le risposte dei differenti isolati al variare delle condizioni ambientali risultano essere simili. Basandosi sui risultati ottenuti sono state sviluppate equazioni matematiche per spiegare l’effetto dei fattori ambientali sull’incidenza delle infezioni di infiorescenze e bacche, germinazione dei conidi, crescita miceliale e produzione di conidi. Un nuovo modello previsionale è stato sviluppato per predire le infezioni di Botrytis cinerea nei vigneti utilizzando le equazioni sviluppate e seguendo un approccio meccanicistico. Il modello è stato validato per 6 anni (2009-2014) in 13 vigneti localizzati in Italia e Francia. Il nuovo modello risulta essere più completo di quelli proposti finora in letteratura e può essere utilizzato per migliorare le strategie di controllo della muffa grigia nei vigneti. / The aims of this Doctoral work were: i) to investigate the effect of different environmental conditions on biology and epidemiology of B. cinerea strains belonging the two transposon types vacuma and transposa, and ii) develop a new weather-driven mechanistic model in order to predict risk of grey mould in vineyards from early growth of inflorescences to berry ripening. The effect of temperature, wetness duration and relative humidity on infection of Vitis vinifera inflorescences and berries was investigated by artificial inoculation of B. cinerea strains. The effect of temperature, water activity, relative humidity and grape berry composition on conidia germination, colony growth and conidial production was investigated in agar-medium. The results showed that the ability to cause infection was a strain rather than a transposon genotype attribute. Moreover, the general response to different environmental conditions is similar among different B. cinerea strains. Based on these data, equations were developed to account the combined effects of environmental factors on infection incidence, conidia germination, colony growth and conidial production. A new previsional model for Botrytis cinerea infections on grapevine was elaborated using the equations developed and following a mechanistic approach. The model was validated over a 6-year period (2009 to 2014) in 13 vineyards located in different grape-growing areas of Italy and France. The model is more complete than the others proposed in literature and represents an improvement to control grey mould in vineyards.

This thesis presents results from two separate studies. First, the impact of bearer length on yield components within the canopy was investigated in season 2005/06, on a commercially-managed, mechanically-pruned vineyard of Vitis vinifera L. Cabernet Sauvignon in Coonawarra, South Australia. Pruning resulted in the retention of bearers with 1-7 nodes, with the weighted average bearer length being two nodes for the canopy. As bearers of one to five nodes in length were the most common, these were studied. Yield components (on a per shoot basis) were analysed according to the node position on the bearer at which the shoot arose. Both budburst and inflorescence number per node were highest at the distal node positions on each length bearer, even if the nodes were at the same positions from the base of the bearer and would normally be expected to have similar fertility. Budburst appeared to act by modifying inflorescence number per node based on the relative location of each node from the apex of the bearer. Shoots that arose from the most distal node positions had the highest flower number per inflorescence and berry number per bunch. Flower number per inflorescence was significantly higher on two-inflorescence shoots than single-inflorescence shoots. The relationship between bunch size and node position, unlike that between inflorescence number and node position, was dependent on bearer length. The relative size of the inflorescence appeared to be affected more so by the node pOSition at which the shoot occurred on the bearer, as opposed to the actual node position on the shoot at which the inflorescence occurred. There was a positive, non-linear relationship between average fruit yield per bearer and bearer length. Although yield was highest from the bearer with the highest node number (five nodes), there was no significant difference in yield per bearer for the bearers of three to five nodes in length. If average bearer length was increased from two to three nodes, the potential yield gain per bearer is estimated at 38 per cent. The second study presents results of correlations between bunch number and components of bunch weight (flower number and berry number) to investigate co-development of bunch number and bunch size. These data were collected from 4 vineyards in the Limestone Coast Zone of South Australia from Vilis vinifera L. Chardonnay, Shiraz and Cabemet Sauvignon during seasons 2002/03 to 2006/07. The significant correlations found between fertility and both bunch weight and flower number per inflorescence suggest that the same factors that affect bunch number in a particular season will also affect bunch size. When inflorescence primordia were initiated and differentiated under cool conditions, actual bunches per node and flowers per inflorescence were low. Differences in climate between the vineyard sites were found to be minimal and therefore did not strongly affect the magnitude of the yield components at the vineyard sites. Cultural practices at each vineyard site were sufficiently variable to affect fertility levels. Genotype is thought to determine the range of flowers per inflorescence that a variety can potentially carry, whereas actual flower number per inflorescence is thought to be determined by inflorescence primordium initiation and differentiation temperatures, as well as temperatures during budburst. Despite significant correlations between flower number per inflorescence and berry number per bunch, flower number per inflorescence preflowering for Cabemet Sauvignon, Shiraz and Chardonnay is inversely related to actual percentage fruit set. This is possibly a survival mechanism for the grapevine as it allows the vine to maximise yield each season without detriment to its longevity. Bunches per vine accounted for the majority of the seasonal variation in yield per vine. Fluctuations in bunch number per vine (and therefore yield) are likely to be reduced by varying the number of nodes retained per vine according to the relative fruitfulness per node present pre-pruning. This practice is therefore likely to result in the seasonal variation of berries per bunch becoming a stronger driver of yield. The commercial impacts of these studies are two-fold. Data presented will assist growers to understand the reasons for which their pruning regimes are affecting yield production and how these pruning regimes may be modified to achieve a target yield-particularly when growers are faced with seasons of low predicted fertility. In addition, data presented will allow growers to improve their crop forecasting accuracy, with a greater understanding of the link between bunch number and bunch size. In the current situation of oversupply in the wine industry, wineries are adopting a tough stance towards growers over-delivering on their grape contracts. Therefore, any assistance that can be provided to growers on improving accuracy of yield estimates will be beneficial both to the grower and winery. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1352744 / Thesis (M.Ag.Sc.) -- University of Adelaide, School of Agriculture, Food and Wine, 2009

This thesis presents results from two separate studies. First, the impact of bearer length on yield components within the canopy was investigated in season 2005/06, on a commercially-managed, mechanically-pruned vineyard of Vitis vinifera L. Cabernet Sauvignon in Coonawarra, South Australia. Pruning resulted in the retention of bearers with 1-7 nodes, with the weighted average bearer length being two nodes for the canopy. As bearers of one to five nodes in length were the most common, these were studied. Yield components (on a per shoot basis) were analysed according to the node position on the bearer at which the shoot arose. Both budburst and inflorescence number per node were highest at the distal node positions on each length bearer, even if the nodes were at the same positions from the base of the bearer and would normally be expected to have similar fertility. Budburst appeared to act by modifying inflorescence number per node based on the relative location of each node from the apex of the bearer. Shoots that arose from the most distal node positions had the highest flower number per inflorescence and berry number per bunch. Flower number per inflorescence was significantly higher on two-inflorescence shoots than single-inflorescence shoots. The relationship between bunch size and node position, unlike that between inflorescence number and node position, was dependent on bearer length. The relative size of the inflorescence appeared to be affected more so by the node pOSition at which the shoot occurred on the bearer, as opposed to the actual node position on the shoot at which the inflorescence occurred. There was a positive, non-linear relationship between average fruit yield per bearer and bearer length. Although yield was highest from the bearer with the highest node number (five nodes), there was no significant difference in yield per bearer for the bearers of three to five nodes in length. If average bearer length was increased from two to three nodes, the potential yield gain per bearer is estimated at 38 per cent. The second study presents results of correlations between bunch number and components of bunch weight (flower number and berry number) to investigate co-development of bunch number and bunch size. These data were collected from 4 vineyards in the Limestone Coast Zone of South Australia from Vilis vinifera L. Chardonnay, Shiraz and Cabemet Sauvignon during seasons 2002/03 to 2006/07. The significant correlations found between fertility and both bunch weight and flower number per inflorescence suggest that the same factors that affect bunch number in a particular season will also affect bunch size. When inflorescence primordia were initiated and differentiated under cool conditions, actual bunches per node and flowers per inflorescence were low. Differences in climate between the vineyard sites were found to be minimal and therefore did not strongly affect the magnitude of the yield components at the vineyard sites. Cultural practices at each vineyard site were sufficiently variable to affect fertility levels. Genotype is thought to determine the range of flowers per inflorescence that a variety can potentially carry, whereas actual flower number per inflorescence is thought to be determined by inflorescence primordium initiation and differentiation temperatures, as well as temperatures during budburst. Despite significant correlations between flower number per inflorescence and berry number per bunch, flower number per inflorescence preflowering for Cabemet Sauvignon, Shiraz and Chardonnay is inversely related to actual percentage fruit set. This is possibly a survival mechanism for the grapevine as it allows the vine to maximise yield each season without detriment to its longevity. Bunches per vine accounted for the majority of the seasonal variation in yield per vine. Fluctuations in bunch number per vine (and therefore yield) are likely to be reduced by varying the number of nodes retained per vine according to the relative fruitfulness per node present pre-pruning. This practice is therefore likely to result in the seasonal variation of berries per bunch becoming a stronger driver of yield. The commercial impacts of these studies are two-fold. Data presented will assist growers to understand the reasons for which their pruning regimes are affecting yield production and how these pruning regimes may be modified to achieve a target yield-particularly when growers are faced with seasons of low predicted fertility. In addition, data presented will allow growers to improve their crop forecasting accuracy, with a greater understanding of the link between bunch number and bunch size. In the current situation of oversupply in the wine industry, wineries are adopting a tough stance towards growers over-delivering on their grape contracts. Therefore, any assistance that can be provided to growers on improving accuracy of yield estimates will be beneficial both to the grower and winery. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1352744 / Thesis (M.Ag.Sc.) -- University of Adelaide, School of Agriculture, Food and Wine, 2009