A podridão parda do pessegueiro é uma das principais doenças da cultura no Estado de São Paulo e na maioria das regiões produtoras do mundo. No Brasil, seu agente causal é o fungo Monilinia fructicola (Wint) Honey, que infecta ramos, flores e frutos tanto em pré como em pós-colheita. A compreensão do comportamento epidemiológico da podridão parda do pessegueiro em condições tropicais é fundamental para o estabelecimento de estratégias de controle mais eficientes nos pomares brasileiros. Neste contexto o presente trabalho teve como objetivo caracterizar o progresso temporal e a distribuição espacial da epidemia da podridão parda do pessegueiro, em pomares comerciais sob condições naturais de infecção. O estudo foi realizado em áreas comerciais não tratadas e tratadas com fungicidas, em dois pomares no Estado de São Paulo, em 2005 e 2006. Realizaram-se amostragens quinzenais de frutos durante 3 meses após o florescimento. Foram colhidos, pelo menos, 300 frutos por amostragem, os quais foram tratados com o herbicida gramoxone para detecção da infecção latente. A análise temporal dos dados foi realizada por regressão não-linear entre a incidência da doença e o tempo, enquanto a distribuição espacial de frutos doentes foi avaliada por meio do índice de dispersão (D) e da lei de Taylor modificada, que relacionam variâncias observada e binomial. Nos dois anos e locais estudados, a podridão parda apresentou tendência de crescimento exponencial, com baixa incidência no início das amostragens e aumento expressivo no início da maturação dos frutos. O modelo exponencial apresentou melhor ajuste aos dados, nos dois anos e locais de estudo. Em 2005, a incidência da doença chegou a valores máximos no ponto de colheita, atingindo 70% em frutos de plantas tratadas e 66,4% nos de não tratadas. Nesse ano, a incidência da podridão parda em frutos de plantas sem e com fungicidas não diferiram entre si (P>0,05), tanto nos parâmetros do modelo quanto na área abaixo da curva de progresso da doença (AUDPC). Em 2006, as curvas de progresso da doença, para frutos de plantas não tratadas com fungicidas, foram semelhantes entre si e caracterizaram-se pelo rápido aumento da incidência de infecções a partir da maturação dos frutos, chegando, na última avaliação, a 59,17% em Holambra II e 74,37% em Jarinu. O controle químico foi eficiente em 2006, havendo baixa incidência de podridão parda em frutos de plantas tratadas, durante toda safra e nos dois locais. No pomar avaliado em 2005, a agregação de frutos doentes (4,7<D<6,8) foi observada a partir da metade da safra e atribuída a pilhas de frutos mumificados na proximidade do pomar. O padrão espacial aleatório predominou na safra de 2006 nos dois pomares avaliados (0,88<D<1,52). Agregação de frutos doentes foi observada apenas por ocasião da colheita, quando a doença estava distribuída em todo o pomar, indicando haver árvores com muitos frutos doentes e outras com predominância de frutos sadios. O rápido progresso e a distribuição heterogênea da epidemia mostram a importância da eliminação das fontes de inóculo para o controle da doença. / The brown rot of peach is one of the main diseases in peach orchards in the State of São Paulo and in most peach producing regions in the world. In Brazil, brown rot is caused by the fungus Monilinia fructicola and it attacks stems, blossoms and fruits in the pre and post harvest periods. The understanding of the brown rot epidemiologic behavior in tropical conditions is essential to the establishment of more efficient control strategies in Brazilian orchards. In this context, the present work aimed to characterize the temporal progress and the spatial distribution of the peach brown rot in commercial orchards under natural infection conditions. The study was carried out in untreated and fungicide-sprayed commercial areas in Paranapanema and Jarinu, SP, in 2005 and 2006. Fruit samplings were performed fortnightly during 3 months after blooming. At least 300 fruits were collected in each sampling and treated with gramoxone herbicide to detect latent infection. Temporal data analysis was done by non-linear regression between disease incidence (y) and time (x). The spatial pattern of diseased fruit was assessed by the dispersion index (D) and the modified Taylor?s power law which relate observed and binomial variances. During these two years in the area studied, brown rot presented a tendency for exponential growth with low incidence in the beginning of the season and expressive increase in the beginning of fruit ripening. The exponential model presented a better fit to the data for the two year study period. In 2005, the brown rot incidence reached maximum values during the harvest: 70% in treated trees and 66,4% in untreated trees. There was no significant difference (P>0.05) in brown rot incidence in trees with or without fungicide treatment in model parameters as well as in the area under the disease progress curve (AUDPC). In 2006, the disease progress curves for treated and untreated trees were not similar. Disease progress curves for untreated trees were characterized by the rapid increase in infections incidence after the ripening of the fruit, reaching in the last evaluation, 59,17% for Holambra II and 74,37% in Jarinu. Chemical control was effective in 2006, with low brown rot incidence in treated trees throughout the harvest in both sites. In the orchard evaluated in 2005, the aggregation of diseased fruit (4,7<D<6,8) was observed in the second half of the season and attributed to piles of mummified fruit in the orchard?s vicinity. The random spacial pattern was predominant in the 2006 harvest in both orchards evaluated (0,88<D<1,52). Diseased fruit aggregations were observed only at harvest time, while the disease was spread throughout the orchard, indicating that some trees had many diseased fruits while in others the healthy fruit predominated. The quick progress and the heterogeneous distribution of the epidemics demonstrate the importance of eliminating the inoculum sources for the control of this disease.

O controle da podridão parda do pessegueiro (Monilinia fructicola) é realizado essencialmente por aplicações preventivas de fungicidas, em sua maioria sistêmicos com modo de ação específico. O uso contínuo desses fungicidas pode levar à seleção de indivíduos resistentes ao ingrediente ativo e, consequentemente, à perda da eficiência do controle nos pomares. A evolução da população de isolados resistentes ao longo do tempo, na ausência do fungicida, pode ser prevista com estudos de habilidade competitiva entre isolados resistentes e sensíveis. Portanto, a quantificação da adaptabilidade (fitness) e da estabilidade, necessárias para caracterizar os isolados encontrados em campo, auxiliarão nas estratégias antirresistência. Embora a importância da determinação da adaptabilidade de isolados resistentes seja reconhecida, há poucos métodos descritos para a análise da habilidade competitiva. Assim, esse trabalho verificou a adaptabilidade, a estabilidade e a habilidade competitiva de isolados de M. fructicola com diferentes níveis de sensibilidade à azoxistrobina em experimentos in vitro e em frutos de pêssegos (in natura e enlatado) utilizando metodologias de avaliação diversas. A caracterização dos isolados foi realizada in vitro, in vivo e molecularmente. Foram avaliados o diâmetro da colônia e a esporulação in vitro; o período de incubação e de latência, a incidência e a severidade da doença e a esporulação in vivo dos isolados separadamente. Os dados de esporulação in vitro foram submetidos ao teste de Kruskal-Wallis e os dados de crescimento micelial ao teste de Tukey com 5% de probabilidade. Para a análise dos dados in vivo, utilizou-se a análise multivariada. Dez transferências em meio de cultura sem fungicida foram realizadas para o estudo da estabilidade de dois isolados resistentes (SP08435 e SP09839) e um sensível (PR09638). A esporulação, a porcentagem de germinação de conídios e o diâmetro da colônia dos isolados em meio de cultura com fungicida foram avaliados em quatro transferências (inicial, terceira, sexta e última transferência). A habilidade competitiva foi verificada pela evolução da porcentagem de indivíduos resistentes no tempo entre um isolado resistente (SP09839) e um sensível à azoxistrobina (PR09638). Modelos lineares ou modelos lineares generalizados (GLM) foram utilizados para descrever o progresso da proporção do isolado resistente ao longo do tempo. Os isolados resistentes exibiram esporulação in vitro e taxa de crescimento micelial semelhantes aos sensíveis, além de apresentarem-se no mesmo grupo de similaridade que os isolados sensíveis. Nenhuma mutação no cyt b foi associada à resistência de M. fructicola à azoxistrobina (G143A, G137R, e F129L) e em todos os isolados foi observado o íntron antes do códon 143. Mesmo após 10 transferências em meio de cultura sem fungicida, os isolados resistentes à azoxistrobina não reduziram sua sensibilidade nem sua capacidade de esporulação e crescimento fora do pêssego. Independentemente da metodologia utilizada para avaliar a habilidade competitiva, a resistência à azoxistrobina não correspondeu a um custo adaptativo para M. fructicola, pois a proporção do isolado resistente manteve-se inalterada ao longo das transferências. O uso de pêssego enlatado é recomendado na substituição de frutos in natura para experimentos de habilidade competitiva. / Control of brown rot in peaches (caused by Monilinia fructicola) is mainly by preventive applications of fungicides, mostly single-target site. Repeated use of these fungicides can, however, select for resistant pathogen populations, which may result in failure of disease control. The evolution of resistant isolates in a population over time can be predicted with competitive ability assays between sensitive and resistant isolates. Therefore, studies quantifying pathogen fitness and stability are necessary to characterize field isolates and improve anti-resistant strategies. However, there are limited reports concerning the methodology used in competitive ability assays. This study determined the fitness of M. fructicola isolates with different levels of sensitivity to azoxystrobin in trials in vitro and in vivo (in natura and canned peaches) with different monocyclic components. Isolates characterization were carried out in vitro, in vivo and molecularly. Mycelial growth rate and sporulation were estimated in vitro, and disease incidence, severity, lesion sporulation, incubation and latent period were evaluated in peach fruit for sensitive and resistant isolates. Sporulation in vitro data were analyzed by Kruskal-Wallis test and mycelial growth rate with the Tukey test at 5% probability. For the in vivo experiments, multivariate analysis were carried out. Ten consecutive transfers on non-amended media were conducted to determine the stability of isolates (two resistant and one sensitive). Sporulation, percent spore germination and colony diameter on azoxystrobin amended media were also evaluated four times (the first, the third, the sixth and the last transfer). Competitive ability was investigated by testing the percentage increase of resistant individuals five generations after inoculation with a mix of azoxystrobin sensitive and resistant isolates. The competitive ability of sensitive and resistant isolates were compared with different variables as colony-forming unit and spore germination. Linear or generalized linear models (GLM) were adjusted to compare the progress of resistant isolates over time. All resistant isolates had in vitro sporulation and mycelial growth rate similar to sensitive isolates. All isolates sequenced presented an intron close to codon 143 and did not have any of the point mutations commonly associated with resistance to QoI fungicides (G143A, G137R, and F129L). After 10 transfers in PDA, colony diameter of resistant isolates was not reduced in azoxystrobin-amended media with 1 &mu;g.ml-1 nor was their sporulation in vitro For all parameters used to measure competitive ability, no fitness cost was associated to M. fructicola isolates resistant to azoxystrobin. Canned peach is a viable option for studies aiming to determine fitness cost of resistant isolates.

La pourriture brune des fruits (BR), causée par les champignons du genre Monilinia, est une maladie courante qui peut provoquer jusqu’à 40% de pertes de récolte chez la pêche. Toutes les pêches cultivées sont plus ou moins sensibles à la moniliose. Aucune alternative aux traitements chimiques n’est disponible, ce qui rend nécessaire les applications de fongicides jusqu'au stade pré-récolte, qui sont préjudiciables pour l'environnement et peuvent laisser des résidus sur les fruits. Une revue de la littérature compile les connaissances disponibles sur le couple pêcher-monilioses.Le but de cette étude est d'étudier les facteurs de résistance du fruit à M. laxa à différents stades de croissance chez la pêche et de déterminer leur contrôle génétique.Nous avons focalisé d’abord sur quelques cultivars pour étudier l'évolution de la sensibilité des fruits à M. laxa au cours de leur développement en relation avec les caractéristiques structurales et biochimiques des fruits (conductance cuticulaire du fruit, micro-fissures de l’épiderme et composés de surface des fruits). Certains composés ont été détectés pour la première fois chez la pêche. Les résultats ont confirmé que lors de la phase I les fruits immatures sont sensibles à la moniliose. Au stade de durcissement du noyau, les fruits sont résistants, la conductance cuticulaire faible et les niveaux de composés de surface présentaient un pic de teneurs. A l’approche de la maturité, les fruits sont sensibles de nouveau. Au stade I, nous avons exploré le rôle des stomates et de la conductance du fruit immature en relation avec la sensibilité à M. laxa. Une centaine de génotypes d'une descendance interspécifique de pêchers appelée BC2 a été caractérisée par une infection au laboratoire, un suivi de pertes transpiratoires des fruits et une estimation de la densité de stomates (uniquement pour les nectarines). Des symptômes inattendus (une ‘tache claire’ qui ne progresse pas) ont été observés. La conductance cuticulaire était significativement liée à la probabilité d'infection, mais le nombre de stomates n’a montré aucun effet sur la probabilité d'infection. Des QTL contrôlant la résistance des fruits à la moniliose, à la conductance cuticulaire et au nombre de stomates ont été identifiés et des co-localisations observées.A maturité, le contrôle génétique de la résistance à la moniliose et des composés biochimiques de l'épiderme des fruits a été étudié. Pendant trois ans, les fruits de la BC2 ont été infectés avec une suspension de spores de champignon selon deux modalités. La BC2 a affiché une forte variabilité de résistance à la moniliose. Malgré une faible stabilité entre les années, des génotypes à haut niveau de résistance ont été identifiés. De plus en 2015, nous avons exploré la variation des composés de l'épiderme des fruits au sein de la BC2. Les composés phénoliques, les terpènes et dérivés ont été quantifiés par HPLC. La relation entre la résistance à la moniliose et la présence et / ou les niveaux de certains composés de l'épiderme et le contrôle génétique de ces composés ont été étudiés.La moniliose des fruits de pêche est un problème complexe qui est encore loin d'être résolu. Des progrès ont été accomplis dans la connaissance des caractéristiques structurales et biochimiques impliquées dans la résistance et des régions du génome qui pourraient conférer une certaine tolérance à la maladie ont été détectées. Des travaux supplémentaires sont nécessaires pour développer des marqueurs moléculaires pour la sélection assistée par marqueurs. Les résultats obtenus suggèrent que des solutions pour l'avenir résident dans l’association de cultivars tolérants _ moins sensibles aux micro-fissures et à haute teneur en composés épidermiques potentiellement inhibiteurs du développement du champignon _ avec des pratiques culturales réduisant les risques de fissuration des fruits et d'apparition de conditions climatiques favorables à la propagation de la moniliose. / Brown rot (BR) in peach fruit caused by the fungus Monilinia spp. is a common disease that can provoke as much as 30 to 40% losses of crop. Currently, all cultivated peaches are more or less sensitive to BR. No other alternative than chemical treatment is available, hence fungicide applications are required until pre-harvest. Such applications are damaging the environment and may let residues in fruits. A review of literature was accomplished to compile the knowledge scattered in the literature from many years. The aim of this study is to investigate the factors of resistance of the fruit to M. laxa at different stages of fruit growth and their genetic control by studying contrasted genotypes and an interspecific peach progeny. The first focus was made on few cultivars to study the evolution of sensibility of fruits to M. laxa during their development in relation with structural and biochemical characteristics of the fruit, e.g. cuticular conductance, micro-cracks and fruit surface compounds. Some compounds were detected for the first time on peach fruit. The results confirmed that during the stage I immature fruits are susceptible to BR. Fruit cuticular conductance was high probably due to high density of stomata and thin cuticule in formation. In contrary, at pit hardening stage fruits were resistant, cuticular conductance was low and the levels of surface compounds exhibit a peak. When maturity approaches, fruit become susceptible again. With rapid development of the fruit during this stage, the surface compounds were diluted and micro-cracks often appear which resulted in high cuticular conductance. At stage I we explored the different physical characteristics of the immature fruit in relation with susceptibility to M. laxa. A hundred of individuals of an interspecific peach progeny called BC2 were characterized through laboratory infection, monitoring of fruit transpiratory losses and estimating stomata density (only for nectarines). Unexpected symptoms (not progressing ‘clear spot’) were observed. The cuticular conductance was significantly linked to the likelihood of infection, but the stomata number had no effect on the likelihood of infection. QTL controlling fruit resistance to BR, cuticular conductance and stomata number have been identified and some co-locations observed. At maturity stage we investigated the genetic control of BR resistance together with biochemical compounds of fruit epidermis. For three years, mature fruits from the BC2 progeny were infected with two modalities of infection: spray until runoff in the orchard to measure infection probability and drop in the laboratory conditions in order to observe the characters of beginning, progression and speed of infection. The BC2 progeny displayed high variability for BR resistance. Despite low stability between years, genotypes with high level of resistance were identified. In addition in 2015, we explored the variation in epidermis compounds of fruit within the BC2 progeny. Phenolic compounds, terpenoids and derivatives were quantified by HPLC. The relationship between BR resistance and presence and/or levels of certain epidermis compounds and the genetic control of these compounds were investigated. BR of peach fruit is a complex problem which is still far from resolved. Progress has been made in the knowledge of structural and biochemical characteristics involved in BR resistance and regions of the genome that could confer certain disease tolerance have been detected. Further work is needed to develop molecular markers for marker assisted selection. The results obtained suggest that solutions for the future lie in associations of tolerant cultivars _ less susceptible to micro-cracks and with high content of epidermis compounds potential inhibitor of the fungus development _ with cultural practices reducing both risks of fruit cracking and occurrence of micro-climatic conditions favorable to BR spread and sporulation.

We report here the draft genome of Kretzschmaria (Ustulina) deusta, an ascomycetous fungus that colonizes and substantially degrades hardwood and can infest living broad-leaved trees. The genome was assembled into 858 contigs, with a total size of 46.5 Mb, and 11,074 protein-coding genes were predicted.

Doctor of Philosophy / Department of Plant Pathology / Christopher R. Little / Charcoal rot, caused by the necrotrophic fungus, Macrophomina phaseolina (Tassi) Goid., is an important disease in sorghum (Sorghum bicolor (L.) Moench). The molecular interactions between sorghum and M. phaseolina are poorly understood. In this study, a large-scale RNA-Seq experiment and four follow-up functional experiments were conducted to understand the molecular basis of charcoal rot resistance and/or susceptibility in sorghum. In the first experiment, stalk mRNA was extracted from charcoal-rot-resistant (SC599) and susceptible (Tx7000) genotypes and subjected to RNA sequencing. Upon M. phaseolina inoculation, 8560 genes were differentially expressed between the two genotypes, out of which 2053 were components of 200 known metabolic pathways. Many of these pathways were significantly up-regulated in the susceptible genotype and are thought to contribute to enhanced pathogen nutrition and virulence, impeded host basal immunity, and reactive oxygen (ROS) and nitrogen species (RNS)-mediated host cell death. The paradoxical hormonal regulation observed in pathogen-inoculated Tx7000 was characterized by strongly upregulated salicylic acid and down-regulated jasmonic acid pathways. These findings provided useful insights into induced host susceptibility in response to this necrotrophic fungus at the whole-genome scale. The second experiment was conducted to investigate the dynamics of host oxidative stress under pathogen infection. Results showed M. phaseolina’s ability to significantly increase the ROS and RNS content of two charcoal-rot-susceptible genotypes, Tx7000 and BTx3042. Over-accumulation of nitric oxide (NO) in stalk tissues in the pathogen-inoculated susceptible genotypes was confirmed using a NO-specific fluorescent probe and confocal microscopy. Significantly increased malondialdehyde content confirmed the enhanced oxidative stress experienced by the susceptible genotypes after pathogen inoculation. These findings suggested the contribution of oxidative stress-associated induced cell death on charcoal rot susceptibility under infection. In the third functional experiment, the behavior of the sorghum antioxidant system after pathogen inoculation was investigated. M. phaseolina significantly increased the glutathione s-transferase (GST), glutathione peroxidase (GPX), glutathione reductase (GR), and peroxidase activities of the susceptible genotypes (Tx7000, BTx3042) but not in the resistant genotypes (SC599, SC35). Increased activities of these enzymes in susceptible genotypes may contribute to reduced oxidative stress thus lowering charcoal rot susceptibility. The fourth functional experiment was designed to quantify induced host-derived cell wall degrading enzymes (CWDEs) using crude enzyme mixtures from stalks. A gel diffusion assay revealed significantly increased pectinesterase activity in pathogen-inoculated Tx7000 and BTx3042 while significantly increased polygalacturonase activity was determined by absorbance. Fluorimetric determination of cell extracts revealed significantly increased cellulose degrading enzyme activity in M. phaseolina-inoculated Tx7000 and BTx3042. These findings revealed the pathogen’s ability to promote charcoal rot susceptibility in grain sorghum through induced host CWDEs. The last functional study was designed to profile the stalk tissue lipidome of Tx7000 and SC599 after M. phaseolina inoculation using automated direct infusion electrospray ionization-triple quadrupole mass spectrometry (ESI-MS/MS). M. phaseolina significantly decreased the phytosterol, phosphatidylserine, and ox-lipid contents in Tx7000 while significantly increasing stigmasterol:sitosterol ratio. Except for ox-lipid content, none of the above was significantly affected in resistant SC599. Results suggested the lethal impacts of M. phaseolina inoculation on plastid- and cell- membrane integrity and the lipid-based signaling capacity of Tx7000. Findings shed light on the host lipid classes that contribute to induced charcoal rot susceptibility in grain sorghum.

2 p. / Alfalfa varieties differ in fall dormancy, defined as growth during the fall. Nondormant alfalfa varieties are usually planted in mild winter areas for their ability to grow in the fall. However, fall growth of nondormant alfalfa may be undesirable in areas subject to repeated frosts or freezes. Nondormant, very nondormant, and extremely nondormant alfalfa varieties (fall dormancy class 8, 9, and 10) are adapted to elevations below 4000 feet in Arizona. Other dormancy classes not included in this publication are moderately nondormant varieties (fall dormancy class 7) which may be grown from 3000 to 5000 feet, and semi-dormant and dormant varieties (fall dormancy 6 and below) which are adapted to colder winter areas above 4000 feet.

Pectobacterium carotovorum subsp. brasiliense (Pcb) is a plant pathogenic bacterium that causes blackleg and tuber soft rot disease of potato worldwide. Pectobacterium spp. are characterized by the secretion of large quantities of plant cell wall degrading enzymes. As the name indicates, Pectobacteria are pectinolytic pathogens, producing enzymes such as pectate lyase, polygalacturonase, and many others that are used to catalyse the breakdown of pectin, the main plant cell wall component. Consequently, virulence of Pectobacteria is highly reliant upon the production and secretion of macerating enzymes. Hence these bacteria are also referred to as “brute-force” pathogens. Infection and disease symptoms on plants commonly result in the development of blackleg disease, a characteristic black-like decay extending on the stems of infected potato plants. Furthermore, the infection of tubers results in the development of soft rot disease. Pcb is of particular interest in that among Pectobacterium spp. such as Pectobacterium atrosepticum (Pa), P. carotovorum subsp. carotovorum (Pcc), and P. wasabiae, Pcb strains are reported to be the most aggressive and virulent pathogens causing blackleg and soft rot disease of potato in many growing regions across the world. The fact that strains of Pcb were recently reported and isolated in South Africa has necessitated that this work be undertaken in order to characterise this newly described important pathogen of potato in regard to its phenotypic, genetic diversity, virulence and host range traits. Therefore in this work Pcb strains were subjected to multilocus phylogenetic analyses (MLSA) in order to investigate and determine whether there is any interspecies and intraspecies genetic diversity among the South African Pcb isolates. It was thus established that there is a significant genetic diversity that exists both on an interspecies and intraspecies level among Pcb isolates. As a result we sought to investigate further if the level of genetic diversity observed can be reflected in terms of the pathogen’s virulence, biochemical, phenotypic as well as host range characteristics. The results of virulence assays on potato tubers and stems indicated that Pcb strains are significantly much more virulent on potato compared to closely related Pectobacterium spp. such as Pa and Pcc. Moreover, the level of intraspecies diversity observed through phylogeny was also evident and reflected on the phenotypic, virulence and host range characteristics of the pathogen. This study also focused on investigating virulence factors employed by Pectobacterium spp. during infection. Such factors include the ability to produce and secrete of various extracellular macerating enzymes, as well as screening for the presence of virulence associated effectors and phytotoxin genes. It was of interest to observe that Pcb strains have the ability to grow and produce substrate-degrading enzymes much more rapidly compared to Pa and Pcc. This phenomenon was also observed in virulence assays where Pcb strains were noted to cause more rapid and most severe maceration symptoms on potato tubers and stems. Thus in agreement with other studies, our results suggests that Pcb is a uniquely sophisticated but diverse plant pathogen which can be considered to be one of the most aggressive causal agents of blackleg and soft rot disease of potato in South Africa. / Dissertation (MSc)--University of Pretoria, 2013. / gm2014 / Microbiology and Plant Pathology / Unrestricted

Please read the Summary in the section 00front of this document / Thesis (PhD)--University of Pretoria, 2005. / Genetics / Unrestricted

Nous nous sommes intéressés dans cette étude à l'estimation de la loi de la durée de séjour en prenant en compte les individus sur lesquels l'évènement d'intérêt et la censure peuvent se produire dans un même intervalle et être observés. Pour cela, nous avons proposé deux approches d'estimation non paramétrique basées sur une approximation asymptotique quand la longueur de l'intervalle entre deux dates consécutives d'observation tend vers 0. La première est basée sur une relation intégrale et la deuxième est basée sur une restauration des durées de séjour. Nous nous sommes servis de ces approches pour monter un modèle de croissance des fruits du cacaoyer en fonction du climat. Nous avons également estimé la sensibilité (probabilité de pénétration et de réussite d'infection) des fruits en fonction de leur stade et le potentiel infectieux (nombre moyen de spores sur un fruit) par date. Ce potentiel infectieux nous permettrait de monter un modèle du potentiel infectieux en fonction des fruits attaqués. La connaissance du potentiel infectieux en fonction des fruits attaqués, de l'estimation de la sensibilité suivant les stades, de l'estimation du modèle de croissance permettra alors de monter un modèle dynamique du potentiel infectieux pour prédire le risque d'évolution de la pourriture brune des fruits du cacaoyer / We are interested in this study in estimating the lifetime distribution by taking into consideration individuals on which the interest event and the censorship can occur in the same intervaland both events were then observed. We proposed two nonparametric approaches based on an asymptotic approximation when the lengthbetween two consecutive observation days tends to 0. The first one was based on an integral relationship and the second one on a lifetime restoration. We used theses approaches to build a fruitgrowth model depending on climatic variables. We also estimated the susceptibility (success probability of attack by a spore on a fruit) of the fruit depending of its developmental stage and theinfectious potential of the disease over time.This infectious potential could help to build a model of infectious potential depending on infected fruits. The knowledge of the infectious potential depending on infected fruits, the estimation of the susceptibility of the fruit and the model of growth will allow to built a dynamic model of infectious potential to predict the evolution risk of disease progression

Os polímeros sintéticos compõem cerca de 20% do lixo urbano no Brasil. Além da não biodegradabilidade, formam uma camada impermeabilizante que impede a passagem de líquidos e gases originados no apodrecimento dos detritos, retardando a estabilização da matéria orgânica. A exploração da madeira produz uma grande quantidade de rejeitos que não são inteiramente aproveitados para gerar energia ou outros produtos, e acarreta sérios problemas ambientais. A finalidade deste trabalho é a produção de compósitos biodegradáveis reunindo rejeitos de madeira e um polímero biodegradável - o poli (álcool vinílico) [PVA]. Para facilitar a degradação do PVA, este foi modificado por anidrido ftálico (AF). A modificação foi estudada através de tempo de gelatinização, calorimetria exploratória diferencial (DSC) e análise termomecânica dinãmica (DMTA). Resíduos da madeira Sugi (Criptomeria japonica) foram refinados até a obtenção de uma farinha com partículas menores que 63 &#181; m. Esta farinha foi adicionada ao meio de reação AF/PVA. As proporções de AF e PVA, bem como os parâmetros utilizados na prensagem foram determinados segundo um planejamento estatístico fatorial. Os compósitos foram moldados a quente (180 C e 50 MPa). Variando-se a proporção AF/PVA, compósitos com valores de módulo de elasticidade (MOE) de &#732;10 GPa e módulo de ruptura (MOR) de &#732;90 MPa na flexão foram obtidos. Os valores são inferiores aos apresentados pelo polímero puro, seco e sem plasticizante (acima de 152 MPa), porém superiores às placas de madeira reconstituída de MDF e OSB, disponíveis comercialmente, que apresentam valores de MOR em torno de 49 MPa. A degradação por microorganismos foi avaliada pelo ensaio de soterramento utilizando uma adaptação do método para avaliar a resistência de materiais lignocelulósicos aos fungos da podridão mole (Publicação IPT No. 1157 D5). Os fungos da podridão mole que ocorreram naturalmente nos compósitos foram isolados e identificados segundo a técnica do microcultivo. O gênero mais frequente foi o celulolítico Trichoderma spp. e o mais degradador foi o Chaetomium spp. As mudanças na estrutura e na morfologia dos compósitos foram estudadas através de espectroscopia de infravermelho (IR) e microscopia eletrônica de varredura (MEV). As perdas de massa e das propriedades mecânicas foram monitoradas em intervalos pré-estabelecidos. Compósitos com altas concentrações de AF apresentaram biodegradabilidades superiores à da madeira maciça de Pinus sp. e levemente inferiores à da madeira de Eucalyptus grandis, utilizadas como referências. A biodegradabilidade se deve à facilidade dos grupos ésteres, dos ftalatos de PVA e de celulose, de serem hidrolizados e de regenerar o ácido ftálico. Mesmo sob hidrólise enzimática, a estrutura PVA-AF-celulose, que forma ligações cruzadas entre microfibrilas de celulose, não se desintegra, conservando as propriedades mecânicas por muito tempo. Estas se mantêm superiores, ao término de 180 dias de exposição, às da madeira maciça de Sugi antes de entrar no processo de biodegradação. Uma correlação entre a estrutura, as propriedades físicas e mecânicas, e a taxa de biodegradação dos compósitos de rejeitos de madeira-PVA foi estabelecida. / Synthetic polymers constitute around 20% of urban solid waste in Brazil. Besides being non-biodegradable, they form an impermeable barrier that prevents the liberation of liquids and gas originated in the waste deterioration, retarding organic matter stabilization. The wood industry produces large amounts of waste wood which is not entirely utilized to produce energy or other products, and it brings several environmental problems. The aim of this study is the production of an environmentally friendly wood-based product composed of waste wood and poly (vinyl alcohol) [PVA]. PVA is the most widely produced water soluble and biodegradable synthetic polymer worldwide. However, PVA degradation in aqueous and soil environments has proved to be quite slow under unadapted conditions. To accelerate its degradation, the PVA has been modified by phthalic anhydride (AF). These modifications have been studied by means of gelation time, Differential Scanning Calorimetry (DSC) and (Dynamic Mechanical Thermal Analysis (DMTA). Sugi (Criptomeria japonica) flour (particles size &#8249; 63 &#181;m) has been obtained by milling waste samples. Wood flour has been added into AF/PVA reaction medium. AF and PVA ratios and pressing conditions have been set by factorial design. The final pressing temperature and pressure have been set as 180 &#176;C and 50MPa respectively. Varying AF/PVA ratios, composites presenting modulus of elasticity (MOE) values of &#732;10GPa and modulus of rupture (MOR) of &#732;90 MPa have been obtained. The MOR values are lower than that presented by the pure, dry, no plasticized PVA (higher than 152 MPa), but they are higher than commercial MDF (medium density fiberboard) and OSB (oriented strand board) of around 49 MPa. Degradation by microorganisms has been performed by soil burial test (method adapted from IPT Edition No. 1157 D5). Naturally occurring soft rot fungi have been isolated and identified according to micro cultivation techniques. Most frequent genus has been the cellulolytic Trichoderma spp. and most degrader has been Chaetomium spp. Changes in the composites microstructures and morphology throughout the biodegradation process have been studied by IR and SEM and decreasing in the mechanical properties monitored. The weight Ioss shown by composites with high AF concentration has been higher than the softwood Pinus sp. and comparable to the hardwood Eucalyptus grandis, utilized as witnesses. Even under enzymatic hydrolysis, the PVA-AF-cellulose structure has been only slightly broken, preserving considerable mechanical properties that remain superior to solid Sugi before entering any biodegradation process, even after 180 days of exposure. A correlation has been established between the structure, physical and mechanical properties and biodegradation rate of waste wood-PVA composites