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Entre as doenças que trazem preocupações e podem causar prejuízos no setor canavieiro em todo o Brasil, destaca-se a ferrugem marrom, causada pelo fungo Puccinia melanocephala H. & P. Sydow. Essa doença ocorre em todas as regiões canavieiras do mundo, desde a Ásia e a África, de onde o complexo \"Sacharum spp.\" é originário, até as Américas e Oceania. No Brasil, a ferrugem foi detectada, pela primeira vez em 1986, no município de Capivari-SP e logo em seguida em Pernambuco e Alagoas. Desde o primeiro surgimento no Brasil, a ferrugem tem sido mantida sob controle, com grande parte das cultivares apresentando resistência. O conhecimento acerca da estrutura populacional de P. melanocephala é necessário para desenvolver estratégias satisfatórias no controle desta doença e no desenvolvimento de cultivares resistentes. A variabilidade genética entre isolados pode ser avaliada por meio de marcador molecular microssatélite e os dados podem ser usados para monitorar as populações do patógeno. Este trabalho teve como objetivo avaliar, por meio do desenvolvimento de uma biblioteca enriquecida em locos de microssatélites, a variabilidade genética entre isolados de P. melanocephala bem como avaliar a patogenicidade de isolados de diferentes regiões produtoras de cana-de-açúcar. Primeiramente, os 44 isolados de ferrugem da cana foram identificados por microscopia utilizando estruturas morfológicas dos urediniósporos. Desse total, 34 foram identificadas como P. melanocephala e 10 como Puccinia kuehnni. Por meio da construção da biblioteca enriquecida com locos microssatélites foram desenvolvidos 21 locos para ferrugem marrom, e desse total, 16 apresentaram amplificações satisfatórias e somente quatro foram polimórficos. A variabilidade genética dos isolados de P. melanocephala foi relativamente alta (HT = 0,650). A análise de agrupamento não permitiu a separação dos isolados de P. melanocephala de acordo com sua região de origem. Os índices de diversidade (DST = -0,039) e divergência (GST = -0,061) genética observados sugerem que a variabilidade genética está igualmente distribuída nas regiões estudadas, ocorrendo uma única população heterogênea. As regiões de origem dos isolados utilizadas para avaliação de patogenicidade não apresentaram variações significativas na agressividade. Os resultados obtidos no presente trabalho evidenciam que o melhoramento genético da cana-de-açúcar para resistência a ferrugem marrom deve ser conduzido em locais com clima favorável a ocorrência do patógeno, que possivelmente representam a diversidade genética presente em diferentes regiões de cultivo / Among the diseases that bring concerns and can cause losses in the sugarcane industry in Brazil, stands out the brown rust, caused by the fungus Puccinia melanocephala H. & P. Sydow. This disease occurs in all sugarcane regions of the world, from Asia and Africa, where the complex \"Sacharum spp.\" originates, to the Americas and Oceania. In Brazil, the rust was detected for the first time in 1986 in the region of Capivari-SP and soon after in the Pernambuco and Alagoas. Since the first appearance in Brazil, the rust has been brought under control, with most of the cultivars showing resistance. The knowledge about the population structure of P. melanocephala is necessary to develop suitable strategies to control this disease and the development of resistant cultivars. The genetic variability between isolates can be assessed by means of microsatellite molecular markers and data can be used to monitor populations of the pathogen. The aim of this work was to develop a library enriched for microsatellite loci in P. melanocephala and assessment of pathogenicity of isolates from three different sugarcane regions producing. First, the 44 sugarcane rust isolates were identified by microscopy using morphological structures of urediniospores. Of this total, 34 were identified as P. melanocephala and 10 as P. kuehnni. Through the construction of the library enriched with microsatellite loci were developed 21 loci brown rust of those, 16 had satisfactory PCR amplifications and only four were polymorphic. The genetic variability of isolates of P. melanocephala was relatively high (HT = 0.650). The cluster analysis did not allow the separation of isolates of P. melanocephala according to their region of origin. The index of the genetic diversity (DST = -0.039) and genetic divergence (GST = -0.061) suggest that genetic variability is equally distributed in the regions studied, occurring only a heterogeneous population. The regions of origin of isolates used for pathogenicity assessment did not show significant variations in aggressiveness. The results obtained in this work show that the genetic improvement of sugarcane for resistance to brown rust should be conducted in areas with favorable weather for the occurrence of the pathogen, which may represent the genetic diversity present in different sugarcane regions

Entre as doenças que trazem preocupações e podem causar prejuízos no setor canavieiro em todo o Brasil, destaca-se a ferrugem marrom, causada pelo fungo Puccinia melanocephala H. & P. Sydow. Essa doença ocorre em todas as regiões canavieiras do mundo, desde a Ásia e a África, de onde o complexo \"Sacharum spp.\" é originário, até as Américas e Oceania. No Brasil, a ferrugem foi detectada, pela primeira vez em 1986, no município de Capivari-SP e logo em seguida em Pernambuco e Alagoas. Desde o primeiro surgimento no Brasil, a ferrugem tem sido mantida sob controle, com grande parte das cultivares apresentando resistência. O conhecimento acerca da estrutura populacional de P. melanocephala é necessário para desenvolver estratégias satisfatórias no controle desta doença e no desenvolvimento de cultivares resistentes. A variabilidade genética entre isolados pode ser avaliada por meio de marcador molecular microssatélite e os dados podem ser usados para monitorar as populações do patógeno. Este trabalho teve como objetivo avaliar, por meio do desenvolvimento de uma biblioteca enriquecida em locos de microssatélites, a variabilidade genética entre isolados de P. melanocephala bem como avaliar a patogenicidade de isolados de diferentes regiões produtoras de cana-de-açúcar. Primeiramente, os 44 isolados de ferrugem da cana foram identificados por microscopia utilizando estruturas morfológicas dos urediniósporos. Desse total, 34 foram identificadas como P. melanocephala e 10 como Puccinia kuehnni. Por meio da construção da biblioteca enriquecida com locos microssatélites foram desenvolvidos 21 locos para ferrugem marrom, e desse total, 16 apresentaram amplificações satisfatórias e somente quatro foram polimórficos. A variabilidade genética dos isolados de P. melanocephala foi relativamente alta (HT = 0,650). A análise de agrupamento não permitiu a separação dos isolados de P. melanocephala de acordo com sua região de origem. Os índices de diversidade (DST = -0,039) e divergência (GST = -0,061) genética observados sugerem que a variabilidade genética está igualmente distribuída nas regiões estudadas, ocorrendo uma única população heterogênea. As regiões de origem dos isolados utilizadas para avaliação de patogenicidade não apresentaram variações significativas na agressividade. Os resultados obtidos no presente trabalho evidenciam que o melhoramento genético da cana-de-açúcar para resistência a ferrugem marrom deve ser conduzido em locais com clima favorável a ocorrência do patógeno, que possivelmente representam a diversidade genética presente em diferentes regiões de cultivo / Among the diseases that bring concerns and can cause losses in the sugarcane industry in Brazil, stands out the brown rust, caused by the fungus Puccinia melanocephala H. & P. Sydow. This disease occurs in all sugarcane regions of the world, from Asia and Africa, where the complex \"Sacharum spp.\" originates, to the Americas and Oceania. In Brazil, the rust was detected for the first time in 1986 in the region of Capivari-SP and soon after in the Pernambuco and Alagoas. Since the first appearance in Brazil, the rust has been brought under control, with most of the cultivars showing resistance. The knowledge about the population structure of P. melanocephala is necessary to develop suitable strategies to control this disease and the development of resistant cultivars. The genetic variability between isolates can be assessed by means of microsatellite molecular markers and data can be used to monitor populations of the pathogen. The aim of this work was to develop a library enriched for microsatellite loci in P. melanocephala and assessment of pathogenicity of isolates from three different sugarcane regions producing. First, the 44 sugarcane rust isolates were identified by microscopy using morphological structures of urediniospores. Of this total, 34 were identified as P. melanocephala and 10 as P. kuehnni. Through the construction of the library enriched with microsatellite loci were developed 21 loci brown rust of those, 16 had satisfactory PCR amplifications and only four were polymorphic. The genetic variability of isolates of P. melanocephala was relatively high (HT = 0.650). The cluster analysis did not allow the separation of isolates of P. melanocephala according to their region of origin. The index of the genetic diversity (DST = -0.039) and genetic divergence (GST = -0.061) suggest that genetic variability is equally distributed in the regions studied, occurring only a heterogeneous population. The regions of origin of isolates used for pathogenicity assessment did not show significant variations in aggressiveness. The results obtained in this work show that the genetic improvement of sugarcane for resistance to brown rust should be conducted in areas with favorable weather for the occurrence of the pathogen, which may represent the genetic diversity present in different sugarcane regions

La recherche d’une agriculture durable et respectueuse de l’environnement passe par une réduction de l’usage d’intrants de synthèse. L’agroécologie cherche à utiliser les interactions entre les organismes de l’agroécosystème pour optimiser son fonctionnement, comme la régulation naturelle des bioagresseurs. C’est dans cette optique que s’inscrit ce travail de thèse qui étudie l’effet de la fertilisation des cultures sur les épidémies de pathogènes foliaires fongiques des cultures. De plus, nous étudions l’évolution des pathogènes face à des scénarios de fertilisation. Cela questionne la durabilité des pratiques culturales qui participent à la régulation les épidémies. Pour répondre à ces questions, nous avons adopté une démarche de modélisation qui permet de simuler l’effet de différents scénarios de fertilisation. Le point de départ et l’originalité de notre démarche a été de considérer le système hôte-pathogène comme un système ressource-consommateur et d’y appliquer des concepts de l'écologie évolutive pour répondre à ces questions agronomiques. Dans les deux modèles construits durant cette thèse, la fertilisation influence directement la quantité de ressources disponible pour le pathogène. Nous nous y concentrons sur un trait d'histoire de vie du pathogène, la période de latence (durée séparant l'infection du début de la sporulation), qui correspond à la durée minimale d'un cycle infectieux et qui, conditionne la stratégie d'allocation des ressources du pathogène. La latence détermine en effet la quantité de ressource qui sera allouée à la croissance du mycélium (donc sa taille à maturité) et celle qui sera ensuite allouée à la sporulation (en relation avec sa taille). Les modèles développés permettent d'étudier les réponses épidémiologique et évolutive des pathogènes foliaires fongiques à la fertilisation des cultures, avec comme référence le système Blé d'hiver/Rouille brune. Nous avons considéré différentes échelles dans ce travail : depuis la lésion où le pathogène se nourrit directement sur son hôte, jusqu’à la parcelle où se développent les épidémies et au paysage où les flux de spores entre les parcelles sont source d’extension des épidémies dans l’agroécosystème. Un premier modèle, à l'intersection des modèles épidémiologiques "SEIR" et des modèles de populations structurées, couvre les échelles de la lésion à celles de l’épidémie et de la parcelle. Le second modèle, à l'intersection des modèles SEIR et des modèles spatiaux d'épidémiologie du paysage, couvre les échelles de la parcelle au paysage agricole. Nous étudions les dynamiques épidémiologiques et évolutives, en comparant des concepts de fitness empiriques et d’invasion. Nous montrons que la fertilisation des cultures, en déterminant la dynamique des ressources disponibles pour les pathogènes, impacte fortement les épidémies. Nos modèles prédisent que la latence des pathogènes évolue en réponse à des compromis écologiques variés, d’une part pour optimiser l’allocation des ressources au niveau des feuilles, mais également pour gagner la course face à la croissance du couvert. La fertilisation, en changeant les concentrations de métabolites foliaires et les dynamiques de croissance du couvert, impacte donc épidémies et réponses évolutives de la latence des pathogènes. A l’échelle du paysage, l’introduction de pratiques variées de fertilisation dans un paysage préalablement homogène pourrait permettre de réduire les épidémies. Cependant, notre modèle prédit une durée limitée de cet effet du fait de l’évolution et de la diversification des pathogènes dans un paysage hétérogène. Ce travail ouvre la voie à des travaux sur l’effet et la durabilité des pratiques pour réguler les épidémies dans l’agroécosystème. Enfin, nous montrons par un travail de méta-analyse qu’il existe une relation forte entre type trophique et latence du pathogène, suggérant que les différents types de pathogènes répondront différemment à des scénarios de réduction de fertilisation / The quest for a sustainable agriculture requires a reduction in the use of synthetic inputs. In this perspective, agroecology seeks to use interactions between organisms in the agroecosystem to replace inputs by ecosystem services, such as the natural regulation of pests and diseases. In this context, this thesis studies the effect of crop fertilization on epidemics of crop fungal foliar pathogens. We also take into account the evolution of these pathogens in response to fertilization scenarios. This allows us to study the sustainability of agricultural practices that contribute to the regulation of epidemics. To answer these questions, we adopted a modelling approach that simulates the effect of different fertilization scenarios. The starting point and originality of our approach was to consider the pathosystem as a consumer-resource system and to use concepts of evolutionary ecology to answer the abovementioned agronomic questions. In the two models developed in this thesis, fertilization directly determines the quantity of resources available for the pathogen. We focus on one of the pathogen's life history traits, the latent period (time period between infection and the onset of sporulating lesions), which corresponds to the minimum duration of an infectious cycle and constrains the pathogen's resource allocation strategy. The latent period determines the amount of resource that will be allocated to either growth of mycelium (and therefore to pathogen size at maturity) or to sporulation (proportional to the pathogen’s size). The models we developed make it possible to study the epidemiological and evolutionary responses of fungal foliar pathogens to crop fertilization. We parameterized our models according to our biological knowledge of the wheat-rust pathosystem. Our modelling work encompasses different spatial and temporal scales: from the lesion where the pathogen feeds directly on its host, to the field and the landscape where the spores that flow between fields are the source of epidemics in the agroecosystem. The first model, at the intersection of the "SEIR" epidemiological models and structured population models, covers the scales of a lesion, the crop canopy and the field. The second model, at the intersection of SEIR and spatial landscape epidemiology models, covers the scales of the field and the agricultural landscape. We study epidemiological and evolutionary dynamics of pathogen populations by comparing empirical and invasion fitness concepts. We show that crop fertilization, by determining the dynamics of available resources for pathogens, has a strong impact on foliar fungal epidemics. Our models predict that pathogen latent period evolves in response to various ecological trade-offs; on the one hand to optimize resources allocation at the leaf scale, on the other hand to win the race against canopy growth. By changing the leaf metabolite content and the rate of canopy growth, fertilization therefore impacts both epidemics and evolutionary responses of pathogen latent period. At the landscape scale, the introduction of various fertilization practices in a previously homogeneous landscape could help to partially regulate epidemics. However, our model predicts that the beneficial effects of heterogeneity will vanish due to the evolution and diversification of pathogens in heterogeneous landscapes. This work sets the stage for further work on the effect and sustainability of agricultural practices on the regulation of crop epidemics in agroecosystems. Finally, by performing a meta-analysis, we bring out a strong relation between pathogen trophic type and latent period, suggesting that different trophic types of pathogens will respond differently to decreasing fertilization scenarios