Les mécanismes expliquant le maintien de la diversité végétale dans les forêts tropicales sont mal connus. Une hypothèse particulièrement étudiée est l’hypothèse Janzen-Connell qui postule que ces mécanismes sont essentiellement causés par les interactions entre les plantes et leurs ennemis naturels, en particulier les organismes pathogènes. Dans cette thèse, nous nous sommes donc intéressés aux agents pathogènes présents dans les sols d’une forêt guyanaise et à leur lien de spécificité avec les plantes. Dans le cas où l’hypothèse Janzen-Connell serait vérifiée, on peut s’attendre à ce que les plantes structurent les communautés de micro-organismes pathogènes. Nos travaux se sont focalisés sur les Oomycètes et en particulier les Phytophthora, pathogènes des arbres très importants, mais nous nous sommes aussi intéressés aux champignons pathogènes. Ainsi, nous avons développé et comparé des jeux d’amorces PCR spécifiques des Phytophthora et des Péronosporomycètes afin d’étudier ces organismes par metabarcoding. Ces amorces ont ensuite servi à étudier la diversité des communautés de Phytophthora dans des échantillons de sols de deux sites forestiers de Guyane Française prélevés au pied d’arbres appartenant à 10 familles végétales. Une faible diversité a été retrouvée, avec seulement 8 taxons en tout, et la très large dominance d’un complexe d’espèces Phytophthora heveae. La structuration par la plante-hôte de ces communautés est plutôt faible. Dans une étude complémentaire, nous avons analysé la diversité des Oomycètes et des champignons pathogènes dans les sols et les litières de six plantations monospécifiques et au sein d’une forêt naturelle de Guyane. La structuration par l’hôte s’est avérée nulle pour les Oomycètes et faible pour les champignons pathogènes. Enfin, nous n’avons pas réussi à déclencher expérimentalement des mortalités ou dépérissements par des Oomycètes sur le wacapou, une espèce d’arbre guyanaise, via des inoculations de sols de forêt. Au final, les résultats de cette thèse ne supportent pas l’hypothèse selon laquelle les Oomycètes seraient d’importants acteurs du maintien de la diversité végétale dans les forêts tropicales. Par ailleurs, ils nous interrogent sur la faible diversité de ce groupe de microorganismes dans les sols et litières dans un hotspot de diversité végétale. / The mecanisms implied in the maintenance of plant diversity in tropical forests are still poorly known. One particularly studied hypothesis is the Janzen-Connell hypothesis, which posits that these mecanisms are essentially caused by the interactions between plant and their natural enemies, including pathogenic organisms. In this thesis, we looked at the pathogenic organisms present in the soils of a Guyanese forest, and the specificity of their interactions withplants. In the case where the Janzen-Connell hypothesis would be verified, we could expect that pathogenic micro-organisms communities would be structured by plants. Our works focused on Oomycetes and especially the Phytophthora, which are very important pathogens of trees, but we also took an interest on pathogenic Fungi. Thus, we developed PCR primer sets specific of the Phytophthora and Peronosporomycete groups, in order to study these organismsthroughmetabarcoding. These primers were then used to investigate the community of Phytophthora in soils sampled from two French Guiana sites, near trees belonging to 10 families. A low diversity was described, with a total of only 8 taxas, and the overwhelming dominance of the species complex P. heveae. A weak host effect was detected. In a complementary study, we looked at the diversity of Oomycetes and Fungi in soils and litters of six monospecific tree plantations and a Guianese natural forest. Structuration by host appeared to be null for Oomycetes and weak for pathogenic Fungi. Finally, we did not success in trying to experimentally provoke, through forest soil inoculations, Janzen-Connell mortalities due to Oomycetes on the Wacapou, a Guianese tree species. In the end, the results of this thesis do not support the hypothesis that Oomycetes may be important agents of the maintenance of tree diversity in tropical forests. Moreover, they bring some questions about the low diversity of this group of micro-organisms in a tree diversity hotspot.

Maize grey leaf spot (GLS), caused by Cercospora zeae-maydis, and potato late blight (LB), caused by Phytophthora infestans, are foliar diseases of maize and potato, two of the most widely grown crops in KwaZulu-Natal (KZN), after sugarcane and timber. Commercial maize in KZN accounts for just on 4.3% of the national maize crop. This is worth R563 million using an average of the yellow and white maize price for the 2001/02 season (at R1 332.87 ton(-1)). In 2003 KZN produced about 5% of the national potato crop (summer crop: 7531 300 10kg pockets from 2243 hectares). This equates to a gross value of R89.4 million based on an average price of R1 188 ton(-1) in 2001. Successful commercial production of maize and potatoes depends upon control of these diseases by translaminar fungicides with highly specific modes of action. This study extends an existing model available for timing of fungicide sprays for GLS and tests and compares two LB models for two calendar-based spray programmes. The study also evaluated the use of an early blight model which is caused by Alternaria solani, and over the single season of evaluation showed potential for use in KZN. For the GLS model it was found that a number of refinements are needed, e.g., the amount of infected maize stubble at planting and not the total amount of maize residue at planting. Based on two years' data, it was found that for the LB models there are no significant differences in levels of control between using a predicted fungicide programme and a calendar-based programme. The importance of knowing initial infection sites, and hence initial inoculum, was demonstrated. This led to the creation of a KZN LB incidence map, now being used to more accurately time the start of a preventative spray programme and to time the inclusion of systemic fungicides in the preventative spray programme. This study has contributed to the further development and expansion of the Automatic Weather Station Network (AWSN) at Cedara, which now comprises 15 automatic weather stations in KZN. The AWSN is currently used to aid farmers and advisers in decision-making regarding fungicide spray timing for GLS and LB. / Thesis (M.Sc.Agric.)-University of Natal, Pietermaritzburg, 2003.

Potato (Solanum tuberosum L.) is the most important horticultural crop of the world. Late blight (Phytophthora infestans (Mont.) de Bary) is the most important and devastating disease. There is no cultivar with sufficient level of resistance in Brazil being most part of production costs used for its control. Besides late blight resistance, new cultivars should have high tuber quality either for processing or table stock. The objectives of this study were to a) develop progeny of late blight resistant progenitors; b) compare selection for tuber quality in single and eight hill plots; c) identify clones with high tuber quality for processing or table stock; and d) study culture medium to increase growth and sporulation of P. infestans isolates. rosses among late blight resistant clones (SMIJ319-1, SMIJ456-4Y, SMIG274-3, Torridon, Tollocan e Stirling) and clones or cultivars either with high tuber quality or highly adapted were made in a screen house of Fitotecnia Department of Universidade Federal de Santa Maria during 2005. Twenty families were evaluated in single hill during spring 2006. Selected clones were also evaluated in eight hill plots during autumn 2006. Tuber appearance, specific gravity and chip color were assessed in all selected clones of both clonal generations. The 19 selected new clones were then evaluated in twenty hill plots during spring 2006 for tuber appearance, chip color, contents of dry matter, reduced sugars, starch and amylose. Growth and sporulation of P. infestans isolates were assessed in potato-dextrose-agar (PDA), carrot-agar, corn flour-agar, rye B and juice of eight vegetables (V8) culture mediums. A high percentage of clones combined tuber appearance, specific gravity and chip color and were identify in progeny of Tollocan, Stirling, SMIJ319-1 e SMIJ456-4Y. A moderate selection index resulted in 89.4%, 63.9% and 79.8% selections in single hill and 71.2%, 63.9% and 71.4% selections in eight hill plots respectively for tuber appearance, specific gravity and chip color. The clones SMA501-1, SMA508-2, SMA508-4, SMA514-8, SMA514-10, SMA514-11 e SMA520-5 showed high processing potential. The clones SMA504-2, SMA505-2, SMA505-7, SMA506-4, SMA513-2, SMA516-2, SMA517-2, SMA519-1 e SMA520-5 showed high potential either for processing or table stock. The rye B medium increased mycelium growth of P. infestans and the culture mediums PDA and V8 increased sporangium production / A batata (Solanum tuberosum L.) é a olerícola cultivada de maior expressão econômica no mundo e no Brasil,. A principal e mais devastadora doença da cultura é a requeima, causada pelo oomiceto Phytophthora infestans (Mont.) de Bary e a ausência de cultivares brasileiras, com altos níveis de resistência determina que uma grande parcela dos custos de produção sejam empregados para o seu controle. A resistência a requeima por si não determina a aceitação de novas cultivares, que devem apresentar alta qualidade de tubérculo para processamento ou para consumo de mesa. Os objetivos deste estudo foram a) desenvolver progênies de genitores resistentes a requeima; b) comparar a seleção para qualidade de tubérculo em gerações de cova única e oito covas; c) identificar clones de alta qualidade de tubérculo com potencial para processamento industrial ou consumo; e d) determinar o meio de cultura que proporcione o maior crescimento e esporulação de isolados de P. infestans. Foram realizados cruzamentos em telado do Departamento de Fitotecnia da Universidade Federal de Santa Maria durante o ano de 2005. Clones resistentes a requeima (SMIJ319-1, SMIJ456- 4Y, SMIG274-3, Torridon, Tollocan e Stirling) foram cruzados com clones ou cultivares adaptados ou de alta qualidade de tubérculo, resultando em 20 famílias que foram avaliadas e clones selecionados na geração de cova única na primavera de 2005. Os clones selecionados foram também avaliados na geração de oito covas no outono de 2006. A seleção para aparência de tubérculo, gravidade específica e coloração de chips resultou em 19 clones que foram novamente plantados em parcelas de 20 covas na primavera de 2006 e avaliados para aparência de tubérculo, coloração de chips, teores de matéria seca, açúcares redutores, amido e amilose. O crescimento e a esporulação de isolados de P. infestans foram avaliados nos meios batata-dextrose-ágar (BDA), cenoura-ágar, farinha de milho-ágar, B de centeio e suco de oito vegetais (V8). Alta porcentagem de clones que combinam aparência de tubérculo, gravidade específica e coloração de chips foram identificados nas progênies de Tollocan, Stirling, SMIJ319-1 e SMIJ456-4Y. A aplicação de moderado índice de seleção permitiu a identificação de 89%, 63,9% e 79,8% dos clones em cova única e 71,2%, 63,9% e 71,4% em oito covas respectivamente para aparência de tubérculo, gravidade específica e coloração de chips. Os clones SMA501-1, SMA508-2, SMA508-4, SMA514-8, SMA514-10, SMA514-11 e SMA520-5 apresentaram alto potencial para processamento industrial e os clones SMA504-2, SMA505-2, SMA505-7, SMA506-4, SMA513-2, SMA516-2, SMA517-2, SMA519-1 e SMA520-5 apresentam potencial para consumo de mesa ou processamento na forma de fritas tipo palito. O meio B de centeio promoveu o rápido crescimento micelial de P. infestans e os meios de cultura BDA e suco V8 promoveram a maior produção de esporângios

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The occurrence of late blight (Phytophthora infestans (Mont) de Bary) in potato crops is responsible for a large amount of fungicides every season. The use of systems for forecasting and late blight resistant cultivars are important tools to reduce the amount of fungicides and thereby reduce production costs and environmental pollution. The objective of this study was to evaluate forecast systems for late blight occurrence in Macaca, SMIJ461-1, and SMINIA793101-3 potato clones in Santa Maria, RS, Brazil. The experiments were carried out at the experimental area of the Fitotecnia Department during Spring 2006 and Autumn 2007. Meteorological data were collected at the centre of the experimental area with an automatic station and with psicrometric pairs installed at different heights, connected to a datalogger. Thirteen treatments were used arranged in a completely randomized design, with four replications. Treatments were differentiated by using accumulated values of severity, which were calculated by Blitecast and Prophy forecasting systems, and the clones characterized as susceptible (Macaca) and resistant (SMIJ461-1 and SMINIA793101-3) to late blight. The values of severity accumulated had the purpose of indicating the time of fungicide application for late blight control. The use of forecast systems for late blight in potatoes of a susceptible genotype, Macaca, reduced the number of fungicides applications without affecting the productivity of the crop, using the Prophy forecasting system, with accumulation of 20 or 25 severity values. In the Prophy forecasting system with 15 accumulated values of severity, there was a better control of late blight than in the weekly scheme, although, the increase in productivity was not significant. The Blitecast forecasting system was not effective to predict infection to control late blight and, therefore, it must be adjusted, particularly regarding height measurement for relative humidity and air temperature. For resistant clones, the use of forecasting systems for late blight in potatoes has no effect on the disease occurrence and productivity of the crop. / A ocorrência da requeima (Phytophthora infestans (Mont.) de Bary) nas lavouras de batata é responsável pela grande quantidade de fungicidas utilizados em cada época de cultivo. A utilização de sistemas de previsão e de cultivares resistentes à requeima são importantes ferramentas para reduzir a quantidade de fungicidas utilizados e com isso diminuir os custos de produção e a poluição ambiental. O objetivo deste trabalho foi avaliar sistemas de previsão de ocorrência de requeima nos clones Macaca, SMIJ461-1 e SMINIA793101-3 de batata, na região produtora de Santa Maria, RS. Os experimentos foram conduzidos na área experimental do Departamento de Fitotecnia nos períodos de primavera de 2006 e outono de 2007. Os dados meteorológicos foram coletados no centro da área experimental com uma estação automática e com pares psicrométricos instalados em diferentes níveis, conectados a um datalogger. Foram utilizados treze tratamentos arranjados no delineamento inteiramente casualizado, com quatro repetições. Os tratamentos foram diferenciados por meio dos valores de severidade acumulados, que foram calculados pelos sistemas de previsão Blitecast e Prophy, e pelos clones caracterizados como suscetível (Macaca) e resistentes (SMIJ461-1 e SMINIA793101-3) à requeima. Os valores de severidade acumulados tinham a finalidade de indicar o momento de aplicação de fungicida para o controle da requeima. A utilização de sistemas de previsão de requeima da batata, para um genótipo suscetível, Macaca, permitiu reduzir o número de aplicações de fungicidas sem afetar a produtividade dessa cultura, utilizando-se o sistema de previsão Prophy, com acúmulo de 20 ou 25 valores de severidade. No sistema de previsão Prophy, com 15 valores de severidade acumulados, obteve-se melhor controle da requeima do que no esquema Semanal, embora o ganho em produtividade não seja significativo. O sistema Blitecast não foi eficiente para prever o momento de aplicação de fungicida para o controle da requeima e, portanto, para ser utilizado deve sofrer alguns ajustes, principalmente em relação à altura de medida da umidade relativa e temperatura do ar. Para os clones considerados resistentes a utilização de sistemas de previsão de requeima da batata, não tem efeito sobre a ocorrência da requeima e na produtividade da cultura.

Made available in DSpace on 2015-03-26T13:37:40Z (GMT). No. of bitstreams: 1 texto completo.pdf: 748698 bytes, checksum: 0def6367ee5f0d01b1c3dd33ae700eb6 (MD5) Previous issue date: 2009-02-16 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Potato (Solanum tuberosum L.) is cultivated in more than 100 countries and it is the fourth most cultivated crop in the world. But some diseases can be limitaing to potato growth. The late blight of potato, caused by oomycete Phytophthora infestans (Mont.) de Bary is one of the most important diseases worldwide. Potato resistance to late blight is the most important control measure, although little emphasis has been done for disease resistance. Due to this reason, the objective of this work was to study the level of resistance of potato cultivars to late blight. Trials were conducted in Maria da Fé, in the southern area of the state of Minas Gerais, from march 22 to July 8 of 2008. The experiment design followed a complete block design with 34 treatments (represented by each cultivar) with three replications. The plants were inoculated naturally. Yield (PROD) was evaluated weigthing all the potato tubers of all the plants in each replication. Late blight severity was evaluated in every two days starting when the first symptoms were visible using a descriptive scale. The following epidemiological variables were obtained: late blight severity when the epidemics reached 50 % of the cycle of the cultivar (Y50 CULT); relative area under disease progress curves for each cultivar (RAUDPC CULT); time in days of the first symptoms of the disease in each cultivar, until the severity reaches 100% of disease severity (T100 CULT); time in days of the fist symptoms of the disease in each cultivar until 50% of disease severity (T50 CULT); late blight severity when it reaches half the epidemic for the experiment (Y50 EXP); relative area under disease progress curves for the experiment (RAUDPC EXP); time in days for the first symptoms in the experiment until 100% of disease severity (T100 EXP); time in days for the first symptoms in the experiment until 50% of disease severity (T50 EXP); time in days for the first symptoms in the experiment until 0.5 % of disease severity (T0.5 EXP); rate of disease progress (r) and maximum disease severity (Ymax). The cultivars were grouped in four pre- determined levels of disease resistance to late blight, defined by the Euclidian distance as a measure of dissimilarity and complete linkage as hierarchical clustering. The clone IAC 6090 (Ibituaçu) was classified as Resistant (R). The cultivars Aracy, Aracy Ruiva, Colorado and IAPAR Cristina were classified as Moderately Resistant (MR); Baraka, Baronesa, BRS Ana, BRS Elisa, Caesar, Catucha, Emeraude, Florice, Itararé, Markies, Melody, Naturella, Soléia and Voyager were classified as Moderatly Susceptible (MS); Ágata, Almera, Asterix, Atlantic, Canelle, Chipie, Cupido, Éden, Elodie, Eole, Fontane, Gourmandine, Gredine, Monalisa and Opaline were classified as Susceptible (S) to late blight. The cultivars classified as resistant and moderately resistant are of long cycles whereas those classified as moderated susceptible and susceptible are in the majority of short cycle. In the great majority of the cases the more resistant cultivars to late blight have rough skin whereas those more susceptible have smooth skin. The level of late blight resistance and the duration of the cycle of the cultivar influenced the potato yield. The average yield of the R, MR, MS and S cultivars were 37.8, 17.6, 15.3 and 7.2 t/ha, respectively. The Y50 CULT average of the R, MR, MS and S cultivars were 11.0, 7.3, 9.8 and 16.3%, respectively. The RAUDPC CULT average of the cultivars R, MR, MS and S cultivars were 25.0, 27.9, 29.4 and 33.3, respectively. The T100 CULT average of the cultivars R, MR, MS and S cultivars were 72.3, 44.8, 34.0 and 29.3 days, respectively. The T50 CULT average of the cultivars R, MR, MS and S cultivars were 57.6, 33.2, 24.5 and 19.9 days, respectively. The Y50 EXP average of the cultivars R, MR, MS and S cultivars were 8.3, 42.1, 96.5 and 99.8%, respectively. The AACPDR EXP average of the cultivars R, MR, MS and S were 24.3, 47.1, 59.9 and 69.0, respectively. The T100 EXP average of the cultivars R, MR, MS and S cultivars were 76.3, 53.1, 40.9 and 33.6 days, respectively. The T50 EXP average of the cultivars R, MR, MS and S cultivars were 61.6, 41.5, 31.3 and 24.1 days respectively. The T0,5 EXP average of the cultivars R, MR, MS and S cultivars were 22.3, 25.2, 17.8 and 14.2 days, respectively. The average r for the cultivars R, MR, MS and S cultivars were 0.12, 0.26, 0.37 and 0.46, respectively. The average Ymax of the cultivars R, MR, MS and S were 100; 100; 100 e 100%, respectively. / A batateira (Solanum tuberosum L.) é cultivada em centenas de países e a batata é o quarto alimento mais consumido no mundo. A produção de batata é limitada por vários fatores, dentre estes, as doenças têm ocupado lugar de destaque. Dentre as doenças que infectam a batata, não só no Brasil, mas em todo o mundo, a requeima causada pelo oomiceto Phytophthora infestans (Mont.) de Bary é considerada uma das mais destrutivas e de maior importância. O uso de cultivares de batata resistentes à requeima é o modo mais econômico de controle da doença. Entretanto, o nível de resistência à requeima das principais cultivares plantadas no Brasil ainda não é conhecido. Este trabalho teve como objetivo determinar o nível de resistência destas cultivares. Foi conduzido um experimento no município de Maria da Fé - MG, localizado no Sul de Minas Gerais, no período de 22 de março a 8 de julho de 2008. O delineamento utilizado foi o de blocos casualizados com 34 tratamentos (cada tratamento foi representado por uma cultivar) com três repetições. A inoculação das plantas do experimento foi feita naturalmente. A produtividade (PROD) foi avaliada pesando-se os tubérculos de todas as plantas de cada parcela. Foi quantificada a severidade da requeima a cada dois dias a partir do surgimento dos primeiros sintomas da doença, utilizando uma escala descritiva. A partir dos dados de severidade foram obtidas as seguintes variáveis epidemiológicas: severidade na metade da epidemia para a cultivar (Y50 CULT); área abaixo da curva de progresso da doença relativa para a cultivar (AACPDR CULT); tempo em dias do primeiro sintoma na cultivar até 100% de severidade (T100 CULT); tempo em dias do primeiro sintoma na cultivar até 50% de severidade (T50 CULT); severidade na metade da epidemia para o experimento (Y50 EXP); área abaixo da curva de progresso da doença relativa para o experimento (AACPDR EXP); tempo em dias do primeiro sintoma no experimento até 100% de severidade (T100 EXP); tempo em dias do primeiro sintoma no experimento até 50% de severidade (T50 EXP), tempo em dias do primeiro sintoma no experimento até 0,5% de severidade (T0,5 EXP); taxa de progresso da doença (r) e severidade máxima (Ymax). Para o agrupamento das cultivares em quatro níveis de resistência à requeima pré- definidos, foi utilizada a distância Euclidiana padronizada como medida de dissimilaridade e a ligação completa como técnica hierárquica aglomerativa. O clone IAC 6090 (Ibituaçu) foi classificado como Resistente (R). As cultivares Aracy, Aracy Ruiva, Colorado e IAPAR Cristina foram classificadas como Moderadamente Resistentes (MR). As cultivares Baraka, Baronesa, BRS Ana, BRS Elisa, Caesar, Catucha, Emeraude, Florice, Itararé, Markies, Melody, Naturella, Soléia e Voyager foram classificadas como Moderadamente Suscetíveis (MS). As cultivares Ágata, Almera, Asterix, Atlantic, Canelle, Chipie, Cupido, Éden, Elodie, Eole, Fontane, Gourmandine, Gredine, Monalisa e Opaline foram classificadas como Suscetíveis (S) à requeima. As cultivares classificadas como resistente e moderadamente resistentes são de ciclo mais tardio, enquanto que a maioria das cultivares classificadas como moderadamente suscetíveis e suscetíveis são mais precoces. Na maioria dos casos, as cultivares mais resistentes à requeima possuem pele mais áspera, enquanto que as mais suscetíveis possuem pele lisa. O nível de resistência à requeima e a duração do ciclo da batata influenciaram a produtividade. A PROD média das cultivares R, MR, MS e S foi de 37,8; 17,6; 15,3 e 7,2 t.ha-1, respectivamente. A Y50 CULT média das cultivares R, MR, MS e S foi de 11,0; 7,3; 9,8 e 16,3%, respectivamente. A AACPDR CULT média das cultivares R, MR, MS e S foi de 25,0; 27,9; 29,4 e 33,3, respectivamente. O T100 CULT médio das cultivares R, MR, MS e S foi de 72,3; 44,8; 34,0 e 29,3 dias, respectivamente. O T50 CULT médio das cultivares R, MR, MS e S foi de 57,6; 33,2; 24,5 e 19,9 dias, respectivamente. A Y50 EXP média das cultivares R, MR, MS e S foi de 8,3; 42,1; 96,5 e 99,8%, respectivamente. A AACPDR EXP média das cultivares R, MR, MS e S foi de 24,3; 47,1; 59,9 e 69,0, respectivamente. O T100 EXP médio das cultivares R, MR, MS e S foi de 76,3; 53,1; 40,9 e 33,6 dias, respectivamente. O T50 EXP médio das cultivares R, MR, MS e S foi de 61,6; 41,5; 31,3 e 24,1 dias, respectivamente. O T0,5 EXP médio das cultivares R, MR, MS e S foi de 22,3; 25,2; 17,8 e 14,2 dias, respectivamente. A r média das cultivares R, MR, MS e S foi de 0,12; 0,26; 0,37 e 0,46, respectivamente. A Ymax média das cultivares R, MR, MS e S foi de 100; 100; 100 e 100%, respectivamente.

Orientador: Rumy Goto / Banca: Roberto Lyra Villas Bôas / Banca: Dirceu Maximino Fernandes / Banca: Sebastião Wilson Tivelli / Banca: Arlete Marchi Tavares de Melo / Resumo: Avaliou-se a produtividade, o acúmulo e a exportação de nutrientes por plantas de pimentão (Capsicum annuum L.) enxertadas e não enxertadas, cultivadas sob ambiente protegido. O experimento foi conduzido de agosto de 2003 a maio de 2004 na Escola Técnica Estadual Augusto Tortolero Araújo pertencente ao Centro Estadual de Educação Tecnológica Paula Souza, em Paraguaçu Paulista, SP. Os porta-enxertos utilizados, AF 2638 e AF 2640, possuem resistência à Phytophthora capsici Leonian e Meloidogyne incognita raça 2. Os tratamentos constaram dos híbridos 'Rúbia R' e 'Margarita' sem enxertar, enxertados sobre os dois porta-enxertos e enxertados neles mesmos. O delineamento experimental foi em blocos ao acaso com oito tratamentos, quatro repetições e 15 plantas por parcela. As plantas foram avaliadas quanto a altura da maior haste, altura da primeira bifurcação, precocidade de florescimento, comprimento e número médio de internódios, produção e características dos frutos produzidos em 12 colheitas, massa de matéria verde e seca de folhas, caules e frutos. As análises químicas foram realizadas em uma planta por parcela aos 35, 83, 135, 178 e 213 dias após o transplante, para determinar a marcha de absorção e exportação de nutrientes. Verificou-se que os híbridos enxertados e não enxertados apresentaram produtividades médias de 132 e 153 t ha-1 para as combinações enxertadas de 'Rúbia R' e 'Rúbia R' pé-franco respectivamente e de 144 e 132 t ha-1 para as combinações enxertadas de 'Margarita' e 'Margarita' pé-franco respectivamente. O acúmulo de nutrientes não foi significativamente diferente entre plantas enxertadas e pés-francos, e a ordem decrescente dos nutrientes acumulados foi: K>N>Ca>Mg>P>S. A partir do que foi observado, concluiu-se que, nessas condições, a enxertia em plantas de pimentão não alterou seu desempenho agronômico, nem teve influência sobre a marcha de absorção de nutrientes. / Abstract: It was evaluated the yield, accumulation and exportation of nutrients by sweet pepper plants grafted and non grafted, under protected cultivation. The research was carried out from August 2003 to May 2004, at the Technical School Augusto Tortolero Araújo, part of Paula Souza State Center of Technological Education, in Paraguaçu Paulista, SP, in Brazil. The rootstocks used - AF 2638 and AF 2640, are resistant to Phytophthora capsici Leonian and Meloidogyne incognita race 2. The treatments were constituted of non grafted hybrids 'Rúbia R' and 'Margarita'; grafted on two evaluated rootstocks and grafted on themselves. The experimental design was of completely randomized blocks with eight treatments, four replications and fifteen plants per plot. Five plants were sent for chemical analysis. Evaluations of the total plants height, first fork height, early blossom, length and average number of internodes, total yield and fruits characteristics of 12 harvests, fresh and dry matter of leaves, stems and fruits, were carried out. The samples for the chemical analysis were taken at the 35th, 83th, 135th, 173th and 213th days after transplantation, with the objective of determining the accumulation and exportation of the nutrients. The results proved that the grafted and non grafted plants had average yield, with the average of 132 and 153 t ha-1 for the grafted combinations of 'Rúbia R' and non grafted plants of 'Rúbia R' respectively and 144 and 132 t ha-1 for the grafted combinations of 'Margarita' and non grafted plants of 'Margarita' respectively. The accumulation of the nutrients was equivalent for grafted combinations and non grafted plants, and nutrients in decreasing order of accumulation were: K>N>Ca>Mg>P>S. It was evidenced that grafting sweet pepper plants neither its agronomic performance, nor interfered on the uptake of nutrients' absorption. / Doutor

Dans un contexte de réduction des intrants chimiques, l’utilisation des phytosanitaires naturels stimulant l’immunité végétale ouvre la porte vers une nouvelle approche de protection des plantes. Ces composés éliciteurs regroupés sous le terme de «Stimulateurs des Défenses naturelles des Plantes» (SDP) activent le système défensif de la plante la rendant plus résistante aux bio-agresseurs. Les SDP, de nature diverse, se présentent sous forme de composés uniques ou en mélange dans les extraits végétaux. Au cours de ma thèse, nous avons démontré l’activité SDP des extraits de marc de raisin. Les extraits issus de sous-produits de la vigne, marc de raisin rouge, marc de raisin blanc et pépins de raisin induisent diverses réactions de défense au sein de plantes modèles. Nous avons focalisé notre étude sur l’extrait de marc de raisin rouge (EMR) stimulant l’immunité chez le tabac. Infiltré sur feuilles, l’EMR induit la réponse de type HR caractérisée par l’apparition de lésions chlorotiques et accumulation de composés autofluorescents dans les tissus infiltrés. Ces réactions de défense locales ont été observées également chez l’arabette et la tomate. L’EMR déclenche les réponses LAR et SAR avec l’accumulation des transcrits des gènes de défense dans les feuilles de tabac et ce quelque soit son mode d’application (infiltration ou pulvérisation). Le mode d’action de l’EMR a été abordé sur cultures cellulaires de tabac BY-2. L’EMR induit une forte alcalinisation du milieu extracellulaire avec une mobilisation du calcium (Ca2+), l’expression des gènes de défense et la mort cellulaire. Une étude pharmacologique de la mort cellulaire suggère la mise en place de mort cellulaire programmée (PCD) dans les cellules de tabac. La caractérisation de la voie de signalisation activée par l’EMR a été étudiée avec le mutant NahG de tabac incapable d’accumuler l’acide salicylique (SA). Les réponses de défense (HR, LAR et SAR) sont faiblement induites par l’EMR chez le mutant nahG. L’EMR provoque une réponse de type HR fortement réduite avec une faible accumulation des composés autofluorescents et une diminution drastique de l’accumulation des transcrits des gènes PR suggérant l’intervention du SA dans l’induction des réactions de défense. Le degré de protection induit par l’EMR a été déterminé sur le pathosystème tabac/Phytophthora parasitica. Pulvérisé sur feuilles, l’EMR réduit de 45% les zones infectées par l’oomycète. Ce degré de protection semble être le résultat de l’activité antimicrobienne de l’EMR combinée à l’activité SDP. Aucune protection n’a été observée chez le mutant nahG confirmant l’implication de SA dans la résistance induite par l’EMR. Le fractionnement de l’EMR a permis de simplifier la formule active des extraits de raisin et d’identifier un mélange de molécules potentiellement capables d’induire l’activité SDP. Les composés actifs sont de nature polyphénolique et contiennent de la procyanidine B2 capable à elle seule d’induire la réponse de type HR et l’expression de l’antimicrobien PR1. Cependant, il semble que cette molécule agisse en association avec d’autres composés polyphénoliques pour stimuler le système défensif de la plante. / In order to reduce chemical inputs, the use of natural phytosanitary products stimulating plant immunity are emerging approaches in phytoprotection. These elicitor compounds known as "Plant Defense Inducers" (PDI) activate the plant defense system and improve their resistance to pests attack. PDI are single molecule or mixture of compounds extracted from plant. In my thesis, we demonstrated the PDI activity of different grape marc extracts. The winery byproducts, red grape marc extract, white grape marc extract and grape seed extract all induced various defense reactions in several plant models. We focused our study on the red grape marc extract (GME) which stimulates the immunity system in tobacco plants. When infiltrated into tobacco leaves, GME induced HR-like response characterized by the appearance of chlorotic lesions and accumulation of autofluorescent compounds in infiltrated tissues. Similar local defense reactions have been observed in Arabidopsis thaliana and tomato. GME also triggered LAR and SAR responses and induced defense gene transcript accumulation in tobacco leaves after infiltration or spraying. The GME mode of action was studied using the suspension-cultured cells of tobacco BY-2. GME induced rapid alkalinization of extracellular medium with calcium mobilization, expression of defense genes and cell death. A pharmacological approach of this defensive phenomenon suggests the establishment of programmed cell death (PCD) in tobacco cells. The characterization of the signaling pathway activated by GME was studied using tobacco nahG mutant unable to accumulate salicylic acid (SA). Defense responses (HR, LAR and SAR) induced by GME were impaired in the nahG mutant. GME drastically reduced HR-like response symptoms and PR transcript accumulation. These data suggest the implication of SA in the GME-induced plant defense reactions. The GME-induced protection was evaluated in the model pathosystem of compatible interaction between Nicotiana tabacum and Phytophthora parasitica var. nicotianae (Ppn). GME could reduce by 45% the infected areas induced by the oomycete on tobacco leaves. This level of protection was the result of the combined antimicrobial and PDI actions of GME. GME had no protecting effect against Ppn on NahG leaves evidencing the involvement of SA in the GME-induced resistance. GME fractionation led to identification of a bioactive molecule mixture capable of inducing the PDI activity. The active compounds are polyphenolics and involve procyanidin B2 which is by itself able to induce the HR-like response and PR1 transcript accumulation. This compound should act in combination with other polyphenolic molecules to stimulate the full plant defense reactions.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / The tomato (Lycopersicon esculentum Mill) is an important crop in the world and an important product for trade "in nature and for industry. The amount of fungicides used in tomato crop for control of diseases is high and contributes significantly to production costs of tomato, besides the high risk of intoxication of the applicator and environmental problems. So, the use of disease forecasting systems based on mathematical models to manage the applications of fungicides for foliar diseases control in tomato may to reduce production costs, by decreasing the number of fungicide applications and machinery operation during the culture cycle. The objective was to test the systems for predicting occurrence of late blight (Phytophthora infestans) and early blight (Alternaria solani) on irrigated tomato under two climatic conditions and estimate the cost of deployment. Three experiments were conducted, the first experiment in the spring of 2007, in Santa Maria - RS. The other two were accomplished in Cristalina - GO. There were two seasons of transplanting (01/04/08 and 03/05/08). Used the hybrid U2006 (UNILEVER), with growth habit determined. The spacing between the rows of plants was 1.3 m between plants in rows of 0,3 m. The randomized block design with three replications was used, each plot of 5,2 m wide, consisting of 4 rows of plants with 5 m long. The systems for predicting disease FAST, to early blight, and Blitecast to late blight were used. Irrigation was performed by spraying in Santa Maria and sprinkler, surface drip and subsurface in Cristalina-GO. The results showed that the use of disease forecasting systems is the most appropriate way to control diseases in tomato, as with the use of disease forecasting systems that can significantly reduce the number of fungicide applications in relation the calendar, based on weekly applications in areas with conditions generally unfavorable to the development of disease. Considering the scenarios of reductions of the number of fungicide applications (30, 43 and 65%), compared to the weekly application, in climatic conditions unfavorable to disease development, it is possible to recover the costs of implementing the system prediction in all scenarios. / A cultura do tomate (Lycopersicon esculentum Mill) é uma das mais expressivas culturas no cenário agrícola mundial, constituindo importante produto para o comércio in natura e indústria de extratos. O volume de fungicidas utilizado na cultura do tomateiro no controle das principais doenças é elevado e contribui significativamente nos custos de produção de tomate, além do elevado risco de intoxicação do aplicador e dos problemas ambientais. Nesse sentido, utilização de sistemas de previsão e aviso, baseados em modelos matemáticos para gerenciar o manejo das aplicações de fungicidas para o controle das principais doenças foliares no tomateiro poderá auxiliar na redução dos custos de produção, através da diminuição do número de aplicações de fungicidas e de operações de máquinas durante o ciclo de desenvolvimento da cultura. O objetivo do trabalho foi testar os sistemas de previsão de ocorrência de requeima e alternaria em tomateiro industrial irrigado sob duas condições climáticas e estimar o seu custo de implantação. Foram realizados três experimentos, o primeiro experimento no segundo semestre de 2007, em Santa Maria RS. Os outros dois foram realizados no município de Cristalina GO. Realizaram-se duas épocas de transplante (01/04/08 e 03/05/08). Utilizou-se a cultivar híbrida U2006 (UNILEVER), de hábito de crescimento determinado. O espaçamento entre as fileiras de plantas foi de 1,3 m e entre as plantas nas fileiras de 0,3 m. Utilizou-se o delineamento experimental de Blocos ao Acaso com três repetições, sendo cada parcela de 5,2 m de largura, composta de 4 fileiras de plantas com 5 m de comprimento. Utilizaram-se os sistemas de previsão de doenças FAST, para mancha de alternaria, e BLITECAST, para requeima. A irrigação foi realizada por aspersão em Santa Maria e por aspersão, por gotejamento superficial e subsuperficial em Cristalina. Os resultados mostraram que o uso de sistemas de previsão de doenças é a maneira mais adequada para o controle de doenças na cultura do tomateiro, pois com o uso de sistemas de previsão de doenças se consegue reduzir significativamente o número de aplicações de fungicidas, em relação ao calendário semanal, em regiões com condições geralmente desfavoráveis ao desenvolvimento de doenças. Considerando-se os cenários de reduções do número de aplicação de fungicidas (30, 43 e 65%), em relação ao calendário semanal de aplicação, condições climáticas desfavoráveis ao desenvolvimento de doenças, é possível recuperar os custos de implantação do sistema de previsão em todos os cenários.

Les sols forestiers sont des habitats hétérogènes, véritables réservoirs de microorganismes. Parmi ces microorganismes, les eucaryotes filamenteux (champignons et oomycètes) sont très divers et jouent un rôle important dans le fonctionnement et la durabilité des écosystèmes forestiers. Leur diversité et leur répartition spatiale à différentes échelles sont encore peu connues et les facteurs qui sous-tendent cette dispersion sont encore peu étudiés. Aussi, les objectifs étaient (i) d'exploiter le séquençage haut-débit pour des études d'écologie microbienne à large échelle et valider son application aux communautés d'oomycètes pathogènes en milieu forestier, (ii) de décrire ces communautés microbiennes, en termes de diversité et de structure, à différentes échelles spatiales (locale, régionale et continentale), (iii) de caractériser les variables biotiques et abiotiques structurant ces communautés et (iv) d'évaluer la réponse éventuelle des communautés aux variations climatiques. Une première étude pilote à l'échelle de la parcelle a été suivi de deux études à grande échelle spatiale le long de gradients environnementaux. Des gradients d'altitude et un gradient latitudinal, à l'échelle continentale, ont été utilisés comme gradient climatique. L'étude préliminaire a donc validé l'utilisation du pyroséquençage pour les communautés fongiques, et en particulier pour les espèces ectomycorhiziennes, et apporté des éléments pour établir une méthodologie d'échantillonnage couplée à cette technique. L'application de ces outils moléculaires à l'étude des communautés oomycètes pathogènes reste à optimiser. Les résultats obtenus sur les communautés fongiques telluriques suggèrent que dans l'hypothèse d'un réchauffement climatique, la richesse fongique ne serait pas directement affectée mais la composition des communautés le serait. La composition des communautés fongiques est également fortement liée au pH du sol. Ces résultats sont à affiner en étudiant plus en détail divers groupes taxonomiques et écologiques en lien avec des variables climatiques plus précises. Par ailleurs, de nombreuses perspectives sont envisageables pour améliorer la détection des oomycètes dans les sols forestiers, qui reste un challenge en écologie microbienne / Forest soils are heterogeneous habitats full of microorganisms. In particular, the filamentous eukaryotes (fungi and oomycetes) exhibit a huge diversity and play essential functions in the dynamic and sustainable growth of the forest ecosystem. However, their diversity and their distribution are poorly known; thus, so are the structuring factors of these microbial communities. The main goals were: (i) use a high-throughput pyrosequencing to study soil microbial communities at a broad geographical scale, and particularly to validate its use for the study of soil forest pathogenic oomycete communities, (ii) study the diversity and structure of fungal and pathogenic oomycetes communities at several spatial scales, (iii) identify possible climatic and edaphic variables structuring these communities and (iv) estimate the possible response of these microbial communities to climatic variation. A pilot study was undertaken at the stand scale. Then, two additional studies were carried out along environmental gradients at the regional and continental scales. The use of the pyrosequencing technique was found appropriate for the fungal communities, but difficulties arose in studying the pathogenic oomycete community. At the stand scale, results suggested the soil to be a valuable substitute for the roots to access the ectomycorrhizal richness and composition using pyrosequencing. The results along the broad scale gradients suggested that fungal richness may not be affected by climate warming but that the composition would be. Moreover, our work indicated that soil pH is a major factor explaining fungal community composition. The main conclusions are still to be confirmed and deeper knowledge of the response of different fungal phylum, or family, would be required. The detection and thus the diversity estimation of the pathogenic oomycetes in forest soil remains a current challenge

Les extensines sont des glycoprotéines pariétales appartenant à la famille des HRGPs (Hydroxyprolin-rich glycoproteins) impliquées dans plusieurs fonctions telles que la croissance, le développement et la défense des plantes contre les pathogènes. Toutefois, leur mode d’action dans la réponse immunitaire végétale n’est pas encore bien connu et reste à élucider. Les extensines interviennent dans le renforcement de la paroi, un des premiers remparts cellulaires contre les pathogènes, en se liant entre elles de manière intra- et intermoléculaire. Ce « cross-linking » est catalysé par des enzymes peroxydases spécifiques et nécessite une correcte conformation des extensines, laquelle est conférée par leur partie glycosylée. Dans ce projet de thèse, nous avons donc entrepris d’étudier l’impact de la glycosylation des extensines sur la défense racinaire et tenté de caractériser, de manière préliminaire, des peroxydases potentiellement impliquées dans le « cross-linking » chez Arabidopsis thaliana. Des techniques d’immunocytochimie réalisées sur une sélection de mutants affectés dans la glycosylation des extensines ont révélé une modulation de la distribution des extensines dans la racine d’A. thaliana en réponse à une élicitation avec un peptide bactérien, la flagelline 22. L’un des résultats majeurs de cette étude a été de montrer l’importance de l’arabinosylation des extensines dans la colonisation de la racine par l’oomycète pathogène Phytophthora parasitica. Ainsi, l’ensemble de ces résultats nous apermis d’élaborer un modèle proposant d’illustrer l’importance de l’arabinosylation des extensines dans l’organisation et l’architecture de la paroi, modulant ainsi l’adhésion du pathogène sur les cellules de la racine et influençant in fine la colonisation de cette dernière. / Extensins are cell wall glycoproteins involved in various biological processes including plantprotection. However, their mode of action in plant immunity response is not clearly established and remains to be elucidated. Extensins are able to strengthen the cell wall, one of the first cellular barriers against pathogens, through intra- and intermolecular cross-links. This cross-linking is catalysed by specific peroxidase enzymes and requires a correct conformation of extensins conferred by their glycan moiety. This PhD project aimed to investigate the impact of extensin glycosylation in root defence and to characterize, as a preliminary study, the peroxidases potentially involved in the extensin crosslinking in Arabidopsis thaliana. Through immunocytochemistry techniques on mutants impaired withextensin glycosylation, we have revealed that a modulation of extensin distribution occurs in A. thaliana root in response to elicitation with the bacterial peptide, flagellin 22. We have also showed that extensin arabinosylation plays a major role, although probably indirect, in the root colonization by the pathogen oomycete Phytophthora parasitica. We have therefore elaborated a model proposing to illustrate the importance of extensin arabinosylation in the cell wall organization and architecture,modulating pathogen adhesion on root cells and influencing in fine root colonization.