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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
311

Diversification de la résistance quantitative à la rouille brune du blé, à partir de la caractérisation des composantes de la résistance / Diversification of quantitative resistance in wheat leaf rust, by the characterisation of resistance components

Azzimonti, Gustavo 21 September 2012 (has links)
L'enjeu de la thèse est de proposer une stratégie de gestion durable de la résistance génétique à la rouille brune du blé, basée sur des sources de résistance quantitative. Nous proposons d'identifier des résistances se traduisant par une diminution des performances du pathogène sur les différentes phases du cycle infectieux. Ainsi, l'exercice de contraintes diversifiées sur le pathogène devraient ralentir son adaptation et augmenter la durabilité de la résistance. La confrontation d'un ensemble de génotypes de blé à trois isolats de rouille brune a permis de mesurer le niveau de résistance pour cinq composantes en serre (efficacité d'infection, période de latence, taille de lésion, sporulation par lésion, sporulation par unité de surface sporulante), et à différentes étapes de l'épidémie au champ. Nous avons mis en évidence une grande diversité des composantes affectées, et une variabilité importante pour toutes les composantes. Le développement d'un modèle statistique a permis d'établir que l'ensemble des composantes intervient dans la détermination du niveau de résistance à l'échelle épidémique, mais l'efficacité d'infection et la latence sont les composantes qui jouent le rôle le plus important pour déterminer le niveau de résistance au champ. L'impact d'une composante sur le niveau global de résistance change selon les étapes de l'épidémie. Les trois isolats utilisés ont exprimé un profil d'agressivité contrasté vis-à-vis des différentes composantes. La cartographie des QTLs associés aux différentes composantes de résistance a permis d'établir que la diversité phénotypique observée est liée à une diversité génotypique. / The issue of this thesis is to propose a durable management of genetic resistance to wheat leaf rust, based on quantitative resistance. We propose to identify resistance factors reducing pathogen development across the different stages of the infectious cycle. Diversifying constraints exerted by host resistance on the pathogen development should slow down the pathogen adaptation, and increase resistance durability. A set of wheat genotypes was confronted to three leaf rust isolates, and resistance level was measured for five components in the greenhouse (infection efficiency, latent period, lesion size, spore production per lesion, spore production per unit of sporulating tissue), as well as at different stages of field epidemics. Across the germplasm investigated, the resistance components involved were diversified, and their resistance level varied. Developing a statistical model, we established that all the components are involved in the resistance level observed in field epidemics, the most important components being infection efficiency and latent period. The incidence of a component on the field resistance level varied across epidemic stages. The three pathogen isolates used displayed contrasted aggressiveness profiles, according to the different resistance components. QTL mapping of resistance associated to the different components showed that phenotypic diversity corresponded to genotypic diversity.
312

La différenciation individuelle : processus et mécanismes / Differenciation between persons : process and mecanisms

Guillon, Claude 01 December 2012 (has links)
L’individu développe une existence dans un contexte collectif. Il y progresse dans la durée et se différencie selon le milieu familial, son caractère, les rencontres et les influences. Un collectif est constitué d’individus différenciés. Il existe de nombreux facteurs observables qui interviennent dans la construction d’une existence : le sexe, la religion, la famille, la fratrie, la pression sociale et politique, l’économie, les revenus, la scolarisation, le physique, la psychologie, etc. Une analyse exploite 300 biographies de personnes célèbres des deux siècles passés. Des conclusions importantes sont tirées de ce travail. On mesure ensuite ce que le collectif apporte ou retire à l’individu pour construire son existence. Les variables qui caractérisent un individu sont précisées et conduisent à une formulation théorique et générale. Ce travail s’achève sur une synthèse de quatre approches récentes : géométrie fractale, sensibilité aux conditions initiales, réduction/structuration et théorie des catastrophes / An individual develops his life in a collective context, where he advances throughout his life and becomes different according to his family, his character, his meetings and influences. An individual existence which differentiates people also constitutes a collective living. There are many observable factors in a collectivity which can influence the building of this existence: sex, religion, family, brothers and sisters, physical appearance, schooling, incomes, politics or psychological state. An analysis can be done throughout three hundred biographies of the two last centuries personalities. Then, the opposite procedure will be developed to measure what collectiveness can add or substract to an individual in his own existence building. Variants that characterize a person are defined with precision, there are the basis of a theorical and general formulation. This study ends in the synthesis of four recent approaches: “fractal geometry”, sensitiveness to the initial conditions, reduction structural building and finally theory of catastrophes
313

E-governance in Africa: governing the continent through AU and Nepad websites

Mukhudwana, Rofhiwa Felicia 21 April 2008 (has links)
Africa’s way forward requires integration, democracy, good governance, participation and inclusive communication of all issues. Intergovernmental organizations are essential to facilitate the above mentioned goals. New thinking highlights the role of new media especially the Internet in democracy and governance in Africa. Therefore, the question solicited here is whether e-governance facilitates continental governance in Africa and under what circumstances would this be possible? This research introduced the internet (web) as a distinct medium of communications with distinct features and characteristics. A number of scholars argue that the Internet as a distinct medium of communication can better facilitate the democratizing role of the media in society, while others argues that the internet has not changed the nature of politics since ordinary politics in all its complexity and vitality has invaded and captured cyberspace. These arguments are divided respectively between Technological Determinism and the Social Shaping of Technology. This research investigates (AU, EU and Nepad) e-governance websites in order to understand practices, prospects and challenges of continental e-governance systems. It was found that the AU and Nepad use the websites for institutional information rather than interaction with citizens and online service delivery. However, significant steps are taken to enhance interaction in Nepad. It is therefore recommended that, the AU and Nepad need to invest time and commitment in enhancing interactivity and rising awareness for these e-governance systems. As projected, EU performs much better than the above two in terms of interactivity. This is because it has more experience and internet penetration and uses is widespread in Europe than it is here in Africa.
314

Grounded : Locative art and embodied digitality

Said, Mitchell Andrew 21 October 2008 (has links)
My research is comprised of two connected components – a written report, and an original artwork. In the written segment of the research, I critically assess arguments sourced from digital theorists writing mainly in the 1990s, who positioned “cyberspace” as means of bodily escape, physical transcendence and disconnection from lived reality. I link their writings to a larger notion of technological determinism. I use a combination of theoretical sources and case studies to argue that these determinist attitudes are being challenged by the emergence of a recent artistic practice (termed “locative art”), itself made possible through changes in the understanding of the integration of digital information into the material world. The second part of my research consists of an original locative work, entitled “Tree ID”. It is integrated into my written research in my third chapter, in which I discuss the technical function and conceptual background of the work. “Tree ID” functions alongside my case studies as an artistic response to technological determinism, and, additionally, as a practical investigation into the South African context of locative art.
315

Contribution à la parallélisation automatique : un modèle de processeur à beaucoup de coeurs parallélisant. / Contribution to the automatic parallelization : the model of the manycore parallelizing processor

Porada, Katarzyna 14 November 2017 (has links)
Depuis les premiers ordinateurs on est en quête de machines plus rapides, plus puissantes, plus performantes. Après avoir épuisé le filon de l’augmentation de la fréquence, les constructeurs se sont tournés vers les multi-cœurs. Le modèle de calcul actuel repose sur les threads de l'OS qu’on exploite à travers différents langages à constructions parallèles. Cependant, la programmation multithread reste un art délicat car le calcul parallèle découpé en threads souffre d’un grand défaut : il est non déterministe.Pourtant, on peut faire du calcul parallèle déterministe, à condition de remplacer le modèle des threads par un modèle s’appuyant sur l’ordre partiel des dépendances. Dans cette thèse, nous proposons un modèle alternatif d’architecture qui exploite le parallélisme d’instructions (ILP) présent dans les programmes. Nous proposons de nombreuses techniques pour s’affranchir de la plupart des dépendances architecturales et obtenir ainsi un ILP qui croît avec la taille de l’exécution. L’ILP qu’on atteint de cette façon est suffisant pour permettre d’alimenter plusieurs milliers de cœurs. Les dépendances architecturales sérialisantes ayant été supprimées, l’ILP peut être bien mieux exploité que dans les architectures actuelles. Un code VHDL au niveau RTL de l’architecture a été développé pour en mesurer les avantages. Les résultats de synthèse d’un processeur allant de 2 à 64 cœurs montrent que la vitesse du matériel que nous proposons reste constante et que sa surface varie linéairement avec le nombre de cœurs. Cela prouve que le modèle d’interconnexion proposé est extensible. / The pursuit for faster and more powerful machines started from the first computers. After exhausting the increase of the frequency, the manufacturers have turned to another solution and started to introduce multiples cores on a chip. The computational model is today based on the OS threads exploited through different languages offering parallel constructions. However, parallel programming remains an art because the thread management by the operating system is not deterministic.Nonetheless, it is possible to compute in a parallel deterministic way if we replace the thread model by a model built on the partial order of dependencies. In this thesis, we present an alternative architectural model exploiting the Instruction Level Parallelism (ILP) naturally present in applications. We propose many techniques to remove most of the architectural dependencies which leads to an ILP increasing with the execution length. The ILP which is reached this way is enough to allow feeding thousands of cores. Eliminating the architecutral dependencies serializing the run allows to exploit the ILP better than in actual microarchitectures. A VHDL code at the RTL level has been implemented to mesure the benefits of our design. The results of the synthesis of a processeur ranging from 2 to 64 cores are reported. They show that the speed of the proposed material keeps constant and the surface grows linearly with the number of cores : our interconnect solution is scalable.
316

[en] A GALS APPROACH FOR POGRAMMING DISTRIBUTED INTERACTIVE MULTIMEDIA APPLICATIONS / [pt] UMA ABORDAGEM GALS PARA A PROGRAMAÇÃO DE APLICAÇÕES INTERATIVAS MULTUMÍDIA DISTRIBUÍDAS

RODRIGO COSTA MESQUITA SANTOS 18 March 2019 (has links)
[pt] Neste trabalho, investigamos como garantir duas propriedades no desenvolvimento de aplicações multimídia distribuídas interativas: determinismo e consistência. Determinismo é uma propriedade individual dos nós em uma aplicação distribuída e refere-se à característica de um programa sempre produzir a mesma saída a partir de uma mesma entrada. Consistência é uma propriedade de todo o sistema e está relacionada a todos os nós terem sempre a mesma visão da ordem dos eventos. Avaliamos o uso da linguagem síncrona Céu no contexto de programação multimídia para garantir o determinismo. Em relação à consistência, avaliamos se a arquitetura GALS (Globally Asynchronous Local Synchronous) é capaz de prover consistência. Tradicionalmente, aplicações multimídia são desenvolvidas usando linguagens de domínio específico ou linguagens de propósito geral utilizando frameworks especializados. Nenhuma dessas duas abordagens promove o desenvolvimento de aplicações multimídia distribuídas interativas determinísticas e consistentes. Nossa investigação sobre o uso de linguagens síncronas no campo de multimídia levou ao desenvolvimento de Céu-Media, uma biblioteca multimídia determinística para a linguagem síncrona Céu, e Mars, um middleware GALS para aplicações multimídia distribuídas interativas. Os resultados desta tese indicam que, usando as garantias da linguagem síncrona Céu, é possível desenvolver aplicações multimídia determinísticas usando Céu-Media. Além disso, eles também indicam que o modelo de consistência implementado pelo middleware GALS Mars garante que todos os nós sempre concordem com a ordem dos eventos em uma apresentação distribuída. Nós validamos nossa proposta discutindo o desenvolvimento de aplicações multimídia distribuídas propostas pela comunidade de pesquisa usando Céu-Media e Mars, destacando as principais vantagens e também as desvantagens em usar nossa abordagem. / [en] In this, work we investigate how to guarantee two properties in the development of interactive distributed multimedia applications: determinism and consistency. Determinism is a property of individual nodes in a distributed application and states that a program always produces the same output when fed with the same input. Consistency is a property of the whole system and states that all nodes should have the same view of the order of events. We evaluate the use of the synchronous language Céu in the context of multimedia programming for guaranteeing the determinism property. Regarding consistency, we evaluate the GALS (Globally Asynchronous Locally Synchronous) architecture for enforcing consistency. Traditionally, multimedia applications are developed using either a domain specific language or a general purpose language supported by specialized frameworks. Neither of the two approaches promotes the development of deterministic and consistent interactive distributed multimedia applications. Our investigation of the use of synchronous languages in the multimedia field led to the development of Céu-Media, a deterministic multimedia library for the synchronous language Céu, and Mars, a GALS middleware for interactive distributed multimedia applications. The results of this thesis indicate that using the guarantees of the synchronous language Céu it is possible to develop deterministic multimedia applications using Céu-Media. Furthermore, they also indicate that the consistency model enforced by the GALS middleware Mars guarantees that all nodes always agree upon the order of events in a distributed presentation. We validate our proposal by discussing the development of real-world distributed multimedia applications proposed by the research community using both, Céu-Media and Mars, highlighting the main advantages and also the drawbacks of using our approach.
317

Uma análise histórica de respostas verbais de relacionar behaviorismo radical e determinismo / A historical analysis of verbal responses of relating radical behaviorism and determinism

Guimarães, Rodrigo Pinto 03 June 2005 (has links)
Made available in DSpace on 2016-04-29T13:18:16Z (GMT). No. of bitstreams: 1 Dissertacao Rodrigo Guimaraes.pdf: 1642845 bytes, checksum: 61609dfab09ab8f83ee2fd1178b4081a (MD5) Previous issue date: 2005-06-03 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This study attempted to analyze articles historically from national and international journals that discuss the relationship between radical behaviorism and determinism. Analyzing how authors have related determinism and radical behaviorism means to analyze the verbal behavior of the authors and its controlling variables. Specifically, this study analyze: the distribution of the articles that discuss the relations between radical behaviorism and determinism throughout the years; the journals that they were published; the authorship of the articles; the citation of Skinner s works in these articles; the kind of citation made and the definitions of determinism found in the articles. The verbal responses of the authors were compared to Skinner s verbal responses (as understood by the authors); historical analysis of the theme of this study was identified. The results show that there was a high rate of publication from the end of the 80 s to the beginning of this decade. The Behavior Analyst and Behaviorism and Philosophy were that journals that had more articles published about this theme. 141 different publications of Skinner were cited in the articles. The most common kind of citation was citing some part of Skinner s work directly. The most common definitions of determinism found were those that defined determinism as mechanism causal mode. The second most common definitions of determinism were those that defined determinism as selection by consequences. Seven different types of relations between radical behaviorism and determinism were found. Except for one established relation, all the others were considered determinist: 1) denial of determinism; 2) assertion of determinism (this relation refers to specific verbal responses that explicitly asserts that radical behaviorism is determinist in relation to verbal responses that deny determinism); 3) approximation of mechanistic modes; 4) dissociation from mechanistic modes; 5) dissociation from teleological causal modes; 6) approximation of causal modes that search for the causes of behavior in external environmental variables and 7) approximation of causal modes that consider different levels of determination (e.g. phylogenetic, ontogenetic and cultural). Dissociation from mechanistic models was the most common relation identified in the articles. Few articles made historical analysis. Most of the authors think they have the same position about this theme as did Skinner / Esta pesquisa teve por objetivo analisar historicamente, a partir de periódicos nacionais e estrangeiros, como diferentes autores têm abordado as relações entre behaviorismo radical e determinismo. Analisar como os autores relacionam behaviorismo radical e determinismo é, na verdade, analisar o comportamento verbal destes autores e suas variáveis de controle. Foram analisadas as relações estabelecidas entre behaviorismo radical e determinismo e algumas possíveis variáveis relacionadas a este comportamento Mais especificamente, este trabalho se propôs a analisar: a distribuição das publicações sobre o tema ao longo dos anos; fontes de publicação; autoria dos artigos; os trabalhos de Skinner referenciados e os tipos de referências feitas à estes trabalhos e as definições de determinismo encontradas nos artigos. As respostas verbais dos autores foram comparadas com respostas verbais de Skinner (como entendidas pelos autores) e buscou-se identificar os trabalhos que analisaram o tema a partir de uma perspectiva histórica. Os resultados mostram que houve um pico de publicações sobre o tema a partir do fim da década de 80 até o início da década atual. As fontes que mais publicaram sobre o tema foram os periódicos The Behavior Analyst e Behavior and Philosophy. 141 trabalhos diferentes de Skinner foram referenciados. O tipo de referência mais realizada pelos autores foi transcrição direta (tipo I) seguida pela referência que indica apenas a obra (tipo III). As definições mais comuns foram as que definiram determinismo como mecanicismo, seguidas por definições de determinismo como seleção por conseqüências. Foram encontrados sete tipos diferentes de relações estabelecidas entre behaviorismo radical e determinismo, exceto a primeira relação todas as outras expressam posições deterministas: 1) relações de negação do determinismo; 2) relações de afirmação do determinismo (estas relações referem-se a respostas verbais que explicitamente afirmam que o behaviorismo radical é determinista, em oposição direta a negação de tal relação); 3) aproximação do mecanicismo; 4) afastamento do mecanicismo; 5) afastamento de modelos causais teleológicos; 6) aproximação de modelos que buscam em variáveis ambientais externas ao organismo as causas do comportamento e 7) alinhamento do behaviorismo radical com um modelo de determinação que considera diferentes níveis de determinação. Relação de afastamento do behaviorismo radical de modelos causais mecanicistas foi a mais identificada. Poucos trabalhos realizaram análises históricas sobre o tema. A maioria dos autores julga ter a mesma posição que Skinner sobre o tema
318

Raymond Aron. De la philosophie critique de l'histoire à l'analyse politique / Raymond Aron. From the critical philosophy of history to the political analyses / 雷蒙•阿隆:从历史哲学批判到政治分析

Li, Lan 08 December 2012 (has links)
Notre idée principale est d’essayer de comprendre la pensée politique de Raymond Aron à partir de sa théorie sur l’histoire. Pour nous, derrière sa proclamation d’une politique raisonnable ou progressive existe un support épistémologique, à savoir la proposition d’un déterminisme de probabilité concernant la vérité historique, proposition qui ne peut se constituer que dans le cadre d’une critique de la philosophie spéculative de l’histoire. Dans l’Introduction à la philosophie de l’histoire, Aron tente de surmonter l’antinomie du devenir humain entre unité totale du modèle hégélien-marxiste et pluralité irréductible du modèle d’Oswald Spengler, mais sans tomber dans le piège du relativisme absolu. Plus précisément, sa propre critique de la philosophie de l’histoire se constitue à double niveau : au niveau méthodologique, il essaye de réinterpréter la relation entre la compréhension et l’explication pour établir l’objectivité historique. Et au niveau ontologique, pour éviter une conclusion relativiste, il réintroduit l’idée d’une société humanisée au sens kantien, mais d’une manière moins téléologique et plus régulatrice. Dans le domaine politique, corrélativement, il rejette tout type de messianisme garanti d’avance, car, à ses yeux, ce n’est que par choix et décision instantanée que l’homme fait son histoire, tout en gardant l’espoir de la liberté. Et son libéralisme se différencie du libéralisme purement économique et apparaît à la fois conservateur vis-à-vis de la tradition et essentiellement politique. Notre recherche consistera à montrer comment s’est élaboré, en surmontant les philosophies dogmatiques de l’histoire, ce déterminisme de probabilité ; comment il a su appliquer cette conviction historique à son analyse de la société, notamment en tant que libérale et quel rôle doit jouer, selon lui, un intellectuel face à la politique ; nous reprendrons ensuite sa critique vis-à-vis des intellectuels français, pour l’appliquer au débat entre les intellectuels chinois. / Our main intention is to present the philosophical background of Raymond Aron’s political point of view by way of his theory on historical philosophy. For us, behind his proclamation of a reasonable politics, exists an epistemological support, known as determinism of probability as far as the historical truth is concerned. And this determinism is only possible when it is based on a critique of the speculative philosophy of history. In the book named introduction to a philosophy of history, Aron tries to surpass the antinomy of historical becoming, between total unity of the hegelian-marxiste model and the irreducible plurality of the Oswald Spengler model, and meanwhile without falling into an absolute relativism. More precisely, the historical philosophy of Raymond Aron is dedicated to a two-dimensional constitution. On the epistemological level, he tries to reinterpret the relation between explication and comprehension, by way of circle between these two methods, and aim to, in the end, establish the limit of historical objectivity by introducing a certain determinism of probability; on the ontological level, in order to avoid the relativist conclusion, he keeps the Kantian notion of truth, but in a less teleological and more regulative sense. Correlatively, in the domain of politics, he declines all kind of Messianism who claims to possess in advance the historical truth, because for him, it is only via instant choice and decision based on the liberty that can man creates his history. His liberalism essentially political is different from the neoliberalism, and maintains a conservative attitude towards the tradition. Generally speaking, our research consists of presenting how this determinism of probability is possible, and how Aron applies this philosophical point of view to the political practice, and according to him, what should an intellectual do facing the politics. And we will also discuss his critiques to the idealism of the french intellectual, in order to analyze the debate among the chinese intellectual. / 本文旨在从雷蒙•阿隆的历史观入手来了解其政治观点形成的背景。我们认为,他在政治上主张的一种“合理的政治观”始终是基于他的历史哲学观,即“或然决定论”展开的,而后者,在其博士论文《历史哲学批判导论》一书中得到了很好的阐明。从破除历史理性的二律背反开始,即黑格尔-马克思传统的作为统一体的历史观和以斯宾格勒为代表的不可还原的多样性的历史观,阿隆构建起一种既超越实证主义,又不陷入相对主义(通过引入康德意义上的“真理”概念)的或然决定论。具体言之,他的历史哲学批判基于一种双层面的建构,一方面,在认识论层面,他试图重新阐释说明和理解的关系来维护历史的客观性;在形而上学层面,为了避免相对主义的结论,他引入了康德意义上的“人道主义社会”的概念,并将其视为一种更少目的性而更多调节性的概念。就政治领域而言,与此相对应的,他拒斥任何先定的救世福音说,并且坚信人类的历史只能由每个自由的个体的当下的选择和决定中被创造。他所主张的自由主义,不同于经济自由主义,一方面对传统秉持保守的态度,另一方面,本质上又是一种政治的自由主义。我们的研究将从阿隆对传统的教条的历史哲学的批判起步,揭示其“或然决定论”的观点的形成过程;及其历史观如何影响其政治观的过程,尤其反映于他作为一名知识分子,对历史的态度问题;我们也将讨论他对法国知识分子弊病的批判,并且将这一批判引入对中国知识分子的讨论当中。
319

Livre-arbÃtrio: um debate filosÃfico e neurocientÃfico / Free will: a philosophical and neuroscientific debate

Maria Andreia Ferreira 19 December 2016 (has links)
CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / Sabemos que o problema do livre-arbÃtrio à tratado, pelo menos, desde Epiteto. A liberdade de escolha que âjulgamosâ possuir à algo que supomos ser inerente à natureza humana. AlÃm disso, parece que sà poderemos ser pessoalmente responsÃveis por nossos atos se os realizarmos livremente. Acreditamos que ser responsÃveis por nossas aÃÃes e escolhas à o que nos torna diferentes dos outros animais. No entanto, apesar de todas essas nossas intuiÃÃes, nÃo sà algumas correntes filosÃficas defendem que nÃo somos livres, mas tambÃm a ciÃncia parece nos dizer que somos sistemas ou mÃquinas determinÃsticas. Os resultados de vÃrios experimentos neurocientÃficos tÃm sugerido que nÃo escolhemos conscientemente fazer o que fazemos. E, posto que a noÃÃo de livre-arbÃtrio tem como prÃ-requisito bÃsico a noÃÃo de consciÃncia, entÃo parece que hà um conflito entre nossas intuiÃÃes cotidianas e as conclusÃes cientÃficas e filosÃficas. O objetivo central desta dissertaÃÃo serÃ, nÃo somente analisar a coerÃncia conceitual das diversas teses sobre o livre-arbÃtrio que surgiram na GrÃcia clÃssica e nos estudos neurocientÃficos atuais, mas tambÃm mostrar que as explicaÃÃes que tentam conectar os fenÃmenos subjetivos e objetivos relativos ao problema nos levaram, ao menos, atà o presente momento, a uma lacuna explicativa. Isto Ã, uma lacuna na explicaÃÃo sobre como podemos conectar nossas intuiÃÃes subjetivas sobre como somos os autores de nossas aÃÃes e as explicaÃÃes objetivas sobre como nosso corpo executa tais aÃÃes.
320

Diversité et évolution chez Vitis vinfera L. de traits impliqués dans le syndrome de domestication et dans la biologie de la reproduction / Diversity and evolution of traits implicated in reproduction biology and in domestication syndrom in wild grape (Vitis vinifera ssp. sylvestris) and domesticated grape (Vitis vinifera ssp. sativa)

Picq, Sandrine 09 February 2012 (has links)
La domestication est un processus évolutif complexe au sein duquel les pressions de sélection exercées par l'Homme conduisent à des changements morphologiques et physiologiques importants qui permettent de différencier sans ambigüité les espèces domestiquées de leurs ancêtres sauvages. Les récentes études archéobotaniques, génétiques et génomiques sur différentes plantes annuelles telles que notamment, le maïs (Zea mays L.), le riz (Oryza sativa L.) ou la tomate (Solanum lycopersicum L.) ont considérablement fait progresser notre compréhension de la domestication des plantes. A la différence des espèces annuelles, la domestication des plantes pérennes, en particulier les espèces fruitières, reste énigmatique.Dans ce contexte, l'objectif de ce travail est de contribuer à la compréhension du processus de domestication d'une plante pérenne fruitière emblématique, la vigne (Vitis vinifera L.) à travers l'étude de la diversité et de l'évolution de deux caractères majeurs du syndrome de domestication : la forme du pépin et le système de reproduction. Nos travaux sur la morphologie du pépin appréhendée par la méthode des transformées elliptiques de Fourier ont révélé des relations significatives entre la forme du pépin, le statut taxonomique (sauvage – domestiqué), l'origine géographique des cépages et leurs liens de parenté corroborant les résultats d'analyses génétiques acquises antérieurement. D'autre part, le changement de forme du pépin se produisant au cours de la domestication serait intimement lié à l'augmentation de la taille de la baie due aux pressions de sélection exercée par l'Homme. Concernant la transition de la diécie vers l'hermaphrodisme opérée au cours de la domestication, l'analyse du polymorphisme de séquences du locus du sexe a révélé que les vignes domestiquées seraient les descendantes d'individus mâles capables de produire des baies. Le patron de diversité de ces mêmes séquences corrobore l'idée d'un événement de domestication majeur de la vigne dans le Proche Orient et témoigne de l'existence d'introgressions du compartiment domestiqué par le compartiment sauvage dans l'Ouest du bassin Méditerranéen. / Domestication is a complex evolutionary process in which, human selection pressures lead to great morphological and physiological changes that allow to differentiate domesticated species from their wild ancestors. Recent archaeobotanical, genetic and genomic studies of various annual crops such as maize (Zea mays L.), rice (Oryza sativa L.) and tomato (Solanum lycopersicum L.) have significantly advanced our understanding of plant domestication. However, the domestication of perennial plants, particularly fruit trees, remains poorly documented compared to the domestication of annual crop plants.In this framework, this work aims to contribute to the understanding of the domestication process of the emblematic perennial plant, the grapevine (Vitis vinifera L.) through the study of diversity and evolution of two major traits of the domestication syndrome: the seed shape and the reproductive system. Our work on seed shape based on the method of the elliptic Fourier transforms revealed significant relationships between seed shape, the taxonomic status (wild – domesticated), the geographic origin of cultivars and their parentage relationships, corroborating former results from genetic analysis. On the other hand, seed shape changes occurred during domestication seem to be linked to the increase of the berry size as the consequence of major human selection pressures. Regarding the transition from diecy to hermaphroditism to diecy operated during domestication, the analysis of sequence polymorphism in the sex locus revealed that domesticated grapevine would be the descendant of wild male individuals able to produce berries. The pattern of diversity of these sequences supports the hypothesis of the occurrence of a major domestication event in the Near East and testify of introgressions of Western European cultivars by local wild grapes.

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