While animal steroid hormones are very well known and have been studied for a long time, in plants no steroid substances were known until relatively recently. Only in the second half of the past century brassinosteroids were discovered; later on, their hormonal function in plants was confirmed. Still a lot of unknown remains as regards their function in plant cells. This paper presents in its first part the evidence that brassinosteroids control in maize (Zea mays L.) grown under field conditions not only its morphology and yield but also some developmental/reproduction characteristics like e.g. number of female inflorescences or speed of the development of male inflorescences. Particular response of a plant depends, however, on the type of applied brassinosteroid, its concentration, and last but not least also on a particular maize genotype and developmental stage of the plant during applicatin. Impact of brassinosteroids on primary photosynthetic processes in plants has not been proven under these conditions, neither on the activity of photosystem (PS) I nor on the Hill reaction. No statistically significant differences in the content of photosynthetic pigments have been found either. Another topic dealt with in this thesis is the possible protective influence of brassinosteroids on plants...

The aim of the master diploma work is to investigate origin of Czech populations and genetic variability of almost all Eurasian populations of the European beaver (Castor fiber). For our purposes we collected specimens from Czech populations, reintroduced population in Kirov district in Russia and all European and Asian refugia. At the end of the 19th century the species was on the verge of extinction due to overhunting, surviving only in eight isolated refugial areas. The population size at the end of the 19th century was estimated as 1 200 animals. The number of individuals has increased thanks to the legal protection and reintroductions. The current population size is estimated at 640 000. It is obvious that the populations of beaver have recently undergone severe bottleneck. Beaver was completely extirpated in the Czech Republic in the 18th century. Since the 80th of the 20th century beavers re-established in the Czech Republic due to migration from neighbouring countries and reintroduction programmes, however we knew only little about the origin of beavers in the Czech Republic. I showed that our beavers are derived from individuals in France, Germany, Norway and east Europe. Mitochondrial DNA of Castor canadensis has not been found in Czech beavers. I studied microsatellite loci (first use for...

The Tatra chamois (Rupicapra rupicapra tatrica), an endemic mountain ungulate, occurs in the High Tatra Mts. (northern Slovakia and southern Poland). In the second part of the 20th century several chamois introductions occurred in Slovakia: Tatra chamois (from the High Tatra Mts.) were introduced into the Low Tatra Mts., while Alpine chamois (R. r. rupicapra) into the Veľká Fatra and Slovenský raj Mts. The High Tatra Mts. population underwent several population declines (bottlenecks) and all other Slovak populations were founded from only a few individuals (founder effect). Moreover, because the Low Tatra, Veľká Fatra and Slovenský raj are neighbouring mountain ranges, there is a potential risk of migration and hybridisation between the subspecies. Using 18 microsatellite loci, we studied neutral genetic variability, structure and potential hybridisation in chamois populations in Slovakia. The study is based on 193 samples: 95 tissue and 5 blood samples, and 88 faecal and 5 hair samples. Low genetic variability was found in all populations, the lowest one in High Tatra Mts. population. High values of fixation index, the number of private alleles, and factorial correspondence analysis indicated strong differentiation between the studied populations. Bayesian clustering divided Slovak chamois...

Sisyrinchium micranthum Cav. is an herbaceous plant, one of the rare species of the genus which is described as annual. In Brazil, its distribution occurs throughout the states of Rio Grande do Sul (RS), Santa Catarina (SC), Paraná (PR), São Paulo (SP), and Rio de Janeiro (RJ). The species has a wide morphological variability reported in several studies, and different combinations of morphological features can be observed in the wild. Based on these combinations that characterize various plant profiles, three morphological types have been described as CI, CII and CIII. Sisyrinchium micranthum has three ploidy levels described in the literature whose basic number is x = 8, 2n = 2x = 16, 2n = 4x = 32, and 2n = 6x = 48. To contribute to the knowledge on the taxonomy, reproduction and evolution of the species, this study investigated genetic and cytogenetic characteristics of S. micranthum, as well as aspects of reproductive biology. To study the population genetic structure of S. micranthum in southern Brazil, firstly, nine microsatellite markers were isolated using an enriched genomic library, and characterized in a diploid population. Later, from the analysis of genetic variability with seven markers for 583 plants of 14 sampled sites in the states of RS, SC and PR, populations with individuals of different ploidy levels were observed. An autopolyploid origin was presumed for these polyploids. The gene and allelic diversities were rather similar for most of the accessions. The inbreeding coefficient over all loci showed that S. micranthum exhibited an average excess of heterozygotes (negative inbreeding coefficient value), but the FIS values of individual populations ranged from -0.273 to 0.454. The heterozygote excess could be expected since autopolyploids present polysomic inheritance, which contributes substantially for a high heterozygosity. In addition, the populations were highly structured. The results from the cytogenetic analyses, demonstrated that the variability of S. micranthum is also present in terms of genome organization. Regarding S. micranthum and related species S. laxum Otto ex Sims and S. rosulatum E.P. Bicknell, it was verified that the 18S-26S rDNA varies in number of loci, with a notable reduction of the same in polyploids in relation to diploids, while 5S locus showed a proportional increase in the number of signals as increased ploidy level. The data on genome size (Cx) for the three species studied showed a genome downsizing from diploids to polyploids, and also a small inter and intraspecific variation with respect to the C-value. In terms of reproductive biology, selfing and outcrossing were recorded for the species. Furthermore, crossing between different morphological categories of S. micranthum are compatible as resulted in the formation of fruits. Likewise, the data suggest that S. micranthum and S. laxum do not present complete reproductive isolation. The genetic variability of S. micranthum demonstrated in this study in terms of genetic divergence between populations and variation in rDNA loci number possibly reflect the complex relationship between polyploidy and reproductive aspects of the species. / Sisyrinchium micranthum Cav. est une espèce herbacée, l'une des rares du genre qui est décrite comme annuelle. On la trouve au Brésil dans les états du Rio Grande do Sul (RS), Santa Catarina (SC), Paraná (PR), São Paulo (SP) et Rio de Janeiro (RJ). Cette espèce montre une grande variabilité morphologique signalée dans plusieurs études, et différentes combinaisons de caractères morphologiques peuvent être observées dans la nature. Sur la base de ces combinaisons qui caractérisent les profils de plantes différentes, trois types morphologiques ont été décrits, CI, CII et CIII. Sisyrinchium micranthum a trois niveaux de ploïdie décrits dans la littérature à partir du nombre de base x = 8, 2n = 2x = 16, 2n = 4x = 32 et 2n = 6x = 48. Pour contribuer à la connaissance taxonomique, reproductive et évolutive de l’espèce, cette étude a considéré des caractéristiques génétiques et cytogénétiques de S. micranthum, ainsi que les aspects de la biologie de la reproduction. Pour étudier la structure des populations de S. micranthum dans le sud du Brésil, neuf marqueurs microsatellites ont été isolés à l'aide d'une banque génomique enrichie, et caractérisés dans une population diploïde. A partir de l'analyse de la variabilité génétique avec sept marqueurs pour 583 plantes de 14 localités d’échantillonnage de RS, SC et PR nous avons observé l'existence de populations possédant des individus à différents niveaux de ploïdie. Une origine autopolyploïde a été présumé pour ces polyploïdes. La diversité génique et allélique était à peu près similaire dans la plupart des populations. Le coefficient de consanguinité sur tous les loci a montré que les populations de S. micranthum ont présenté un excès des hétérozygotes (coefficient de consanguinité négative), mais les valeurs de FIS de populations individuelles variaient de -0,273 à 0,454. L'excès d'hétérozygotes peut être dû à un héritage polysomique des autopolyploïdes, ce qui contribue sensiblement à une hétérozygotie élevée. En outre, les populations sont très structurées. Les résultats de l'analyse cytogénétique montrent que la variabilité chez S. micranthum s’exprime aussi en termes d'organisation du génome. En ce qui concerne S. micranthum et les espèces proches S. laxum Otto ex Sims et S. rosulatum E.P. Bicknell, il a été démontré que l'ADNr 18S-26S varie en nombre de loci, avec une réduction importante chez les polyploïdes par rapport aux diploïdes, tandis que le locus 5S a montré une augmentation du nombre de signaux proportionnelle au niveau de ploïdie. Les données sur la taille du génome pour les trois espèces étudiées ont montré une tendance à la baisse du génome monoploïde (1Cx) chez les polyploïdes (« genome downsizing »), ainsi qu’une faible variation inter et intraspécifique de la valeur C. En termes de la biologie de reproduction, l'autofécondation et l’allofécondation ont été observées chez cette espèce. En outre, il a été constaté que des croisements entre différentes catégories morphologiques de S. micranthum ont été possibles puisqu’ils ont abouti à la formation des fruits. De même, les données obtenues suggèrent aussi qu’il n’existe pas une barrière reproductive complète entre S. micranthum et S. laxum. La variabilité génétique de S. micranthum mise en évidence dans cette étude en termes de divergence génétique entre les populations et variation dans le nombre de loci d’ADNr probablement reflètent une relation complexe existante entre la polyploïdie et les aspects de la reproduction de l’espèce. / Sisyrinchium micranthum Cav. é uma planta herbácea, sendo uma das raras espécies do gênero que são descritas como anuais. No Brasil, sua distribuição ocorre ao longo dos estados do Rio Grande do Sul (RS), Santa Catarina (SC), Paraná (PR), São Paulo (SP) e Rio de Janeiro (RJ). A espécie apresenta ampla variabilidade morfológica relatada em vários trabalhos, sendo que diferentes combinações de aspectos morfológicos podem ser observadas na natureza. Baseando-se nessas combinações que caracterizam diversos perfis vegetais, três tipos morfológicos foram descritos, CI, CII e CIII. Sisyrinchium micranthum tem três níveis de ploidia descritos na literatura a partir do número básico x = 8, sendo eles 2n = 2x = 16, 2n = 4x = 32 e 2n = 6x = 48. A fim de contribuir para o conhecimento taxonômico, reprodutivo e evolutivo da espécie, neste trabalho foram investigadas características genéticas e citogenéticas de S. micranthum, assim como aspectos da biologia reprodutiva. Para estudar a estrutura populacional de S. micranthum no sul do Brasil, primeiramente, nove marcadores microssatélites foram isolados usando uma biblioteca genômica enriquecida, e caracterizados em uma população diploide. Posteriormente, a partir da análise da variabilidade genética com sete marcadores para 583 plantas de 14 localidades amostradas nos estados do RS, SC e PR observou-se a existência de populações com indivíduos de diferentes níveis de ploidia, e uma possível origem autopoliploide para os poliploides. As diversidades gênica e alélica foram aproximadamente semelhantes para a maioria dos acessos. O coeficiente de endogamia sobre todos os locos mostrou que S. micranthum apresentou um excesso médio de heterozigotos (valor de coeficiente de endogamia negativo), mas os valores FIS das populações individuais variaram de -0,273 a 0,454. O excesso de heterozigotos poderia ser esperado uma vez que autopoliploides apresentam herança polissômica, o que contribui substancialmente com uma heterozigosidade elevada. Além disso, as populações mostraram-se altamente estruturadas. Os resultados provenientes das análises citogenéticas, mostram que a variabilidade de S. micranthum está presente também em termos de organização do genoma. Considerando S. micranthum e as espécies relacionadas S. laxum Otto ex Sims e S. rosulatum E.P. Bicknell, foi possível verificar que o rDNA 18S-26S varia em número de locos, com notável redução dos mesmos em poliploides em comparação com os diploides, enquanto o loco 5S mostrou aumento proporcional no número de sinais conforme o aumento no nível de ploidia. Os dados relativos ao tamanho do genoma (Cx) para as três espécies estudadas mostraram uma tendência de redução do genoma de diploides para poliploides; e também uma pequena variação inter e intraespecífica com relação ao valor C. Em termos de biologia reprodutiva, foi registrada a ocorrência de autofecundação e fecundação cruzada para a espécie. Além disso, foi verificado que cruzamentos entre as diferentes categorias morfológicas de S. micranthum são compatíveis uma vez que resultaram na formação de frutos. Da mesma forma, os dados obtidos sugerem que S. micranthum e S. laxum não representam táxons totalmente isolados reprodutivamente. A variabilidade genética de S. micranthum encontrada no presente estudo em termos de divergência genética entre populações e de variação do número de locos de rDNA, possivelmente, reflete a complexa relação existente entre a poliploidia e os aspectos reprodutivos da espécie.

No description available.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The common bean (Phaseolus vulgaris L.) is an important calcium source for human diet, thus the evaluation of the calcium use efficiency in common bean a relevant tool for crop sustainability. The aims of this study were to evaluate the response in common bean cultivars with different calcium concentrations in nutrient solution on dry matter production, yield components and calcium, potassium and magnesium accumulations; to investigate the association between these characters; to evaluate the genetic variability of lines for calcium availability in the solution; and identify lines of common bean-efficient and responsive to calcium application by different indexes. For this, three experiments were conducted from March 2011 to July 2012 in greenhouse, in a completely randomized design, in splitplots. In the first two experiments were tested calcium concentrations in nutrient solution from 1.10 to 4.95 mmol L-1 as components of the main plot and the BRS Expedito, Carioca and Iraí cultivars on subplots in the first experiment, with the exclusion of the cultivar Iraí in the second experiment. The third experiment evaluated the efficiency and the response of the calcium use of 12 different common bean lines at low (1.10 mmol L-1) and high (3.85 mmol L-1) calcium concentrations in the nutrient solution. Higher values for dry matter and grain yield components were observed for 3.30 mmol L-1 and 4.95 mmol L-1 calcium concentrations in the solution. The common bean cultivars acumulate greater quantity of calcium in the leaves, followed by stems, pods and grains. Highest accumulation of calcium in the leaves was obtained at a 4.95 mmol L-1 calcium concentration in the nutrient solution, and the calcium concentration in the leaves was 21 times higher than the value obtained in the bean grains. The increase of calcium concentration in the nutrient solution up to the concentration of 4.95 mmol L-1 does not change the absorption and the accumulation of potassium and magnesium in leaves and grains. Indirect selection by greater dry matter and higher values of the variables that form the grain yield in common bean will be efficient to increase the accumulation of calcium in grains. The lines L 15, L 234, L 246 and L 77 respond to the increase on calcium supply in the solution, because more calcium accumulates in grain in the cultivation with high calcium concentration. The lines L 246 and L 15 are calcium use efficient in the plant, in the acquisition and grain production, and are not responsive to calcium application. The line L 77 is calcium use efficient in the plant and in the grain production and is responsive to the calcium application in the nutrient solution. / O feijão (Phaseolus vulgaris L.) é uma importante fonte de cálcio para a alimentação humana, sendo a avaliação da eficiência no uso de cálcio em feijão uma ferramenta relevante para a sustentabilidade da cultura. Foram objetivos desse trabalho avaliar a resposta de cultivares de feijão a diferentes concentrações de cálcio em solução nutritiva na produção de massa seca, nos componentes da produtividade de grãos e no acúmulo de cálcio, potássio e magnésio; investigar a associação entre esses caracteres; avaliar a variabilidade genética de linhagens de feijão quanto a disponibilidade de cálcio na solução e identificar linhagens eficientes no uso de cálcio e responsivas a aplicação deste mineral por diferentes índices. Para isso foram realizados três experimentos no período de março de 2011 a julho de 2012, em casa-devegetação, em delineamento inteiramente casualizado, com parcelas subdivididas. Nos dois primeiros experimentos foram testadas concentrações de cálcio na solução nutritiva de 1,10 a 4,95 mmol L-1 como componentes da parcela principal e as cultivares BRS Expedito, Carioca e Iraí nas subparcelas no primeiro experimento, com a exclusão da cultivar Iraí para o segundo experimento. No terceiro experimento foram avaliadas a eficiência no uso e a resposta de 12 linhagens de feijão em baixa (1,10 mmol L-1) e em alta (3,85 mmol L-1) concentração de cálcio na solução nutritiva. Maiores valores para massa seca e para os componentes da produtividade de grãos foram observados para as concentrações de 3,30 mmol L-1 e de 4,95 mmol L-1. As cultivares de feijão acumulam maior quantidade de cálcio nas folhas, seguido pelos caules, vagens e grãos. Maior acúmulo de cálcio nas folhas foi obtido na concentração de 4,95 mmol L-1 de cálcio na solução nutritiva, quando a concentração de cálcio nas folhas é 21 vezes superior ao valor obtido nos grãos de feijão. O aumento da concentração de cálcio na solução nutritiva até a concentração de 4,95 mmol L-1 não altera a absorção e o acúmulo de potássio e de magnésio nas folhas e nos grãos de feijão. A seleção indireta pela maior massa seca de parte aérea e maiores valores das variáveis que formam a produtividade de grãos em feijão será eficiente para aumentar o acúmulo de cálcio nos grãos de feijão. As linhagens L 15, L 234, L 246 e L 77 respondem ao aumento do suprimento de cálcio na solução, pois acumulam mais cálcio nos grãos em cultivo com alta concentração deste mineral. As linhagens L 246 e L 15 são eficientes no uso de cálcio na planta, na aquisição de cálcio e na produção de grãos, e não são responsivas à aplicação de cálcio. A linhagem L 77 é eficiente no uso de cálcio na planta e na produção de grãos e é responsiva à aplicação de cálcio na solução nutritiva.

O estudo da diversidade genética e o conhecimento das relações entre cultivares melhoradas é fundamental para os programas de melhoramento de soja, pois auxiliam na seleção de genitores e recomendação de cultivares. Esta tese está subdividida em três capítulos, sendo que o primeiro traz o referencial teórico relacionado à cultura, à importância econômica e ao melhoramento da soja. O segundo capítulo, por sua vez, foi desenvolvido com os objetivos de: avaliar a diversidade genética a partir de caracteres fenotípicos de genótipos de soja convencional de ciclo precoce em ambientes distintos; determinar a importância de caracteres na divergência genética de soja; e selecionar genitores de ampla diversidade genética para programa de melhoramento, utilizando diferentes métodos de agrupamento multivariados. O experimento foi conduzido em dois locais distintos, Campo Novo dos Parecis - MT, safra 2010/2011 e Urutaí - GO, safra 2012/2013. Foram avaliados dez genótipos de soja convencional de ciclo precoce, em delineamento de blocos completos casualizados, nos quais foram mensurados oito caracteres agronômicos. Por meio de análises uni e multivariadas, foi possível concluir que os agrupamentos formados por todos os métodos multivariados, aliados às médias dos valores fenotípicos dos genótipos, permitiram inferir sobre as combinações promissoras para hibridações artificiais. Ao considerar os dois ambientes de cultivo, o número de dias para a floração, a altura da planta na maturidade e altura de inserção da primeira vagem foram os caracteres que mais contribuíram para a divergência genética em soja. As linhagens UFU 106 e UFU 108 são as mais recomendadas como parte das hibridações com genótipos divergentes, pois são complementares em produtividade de grãos e menor fase vegetativa. Recomenda-se hibridações entre os seguintes pares de genótipos: UFU 106 x UFU 112; UFU 106 x Emgopa 316; UFU 108 x Emgopa 316; UFU 112 x Emgopa 316, para a obtenção de populações segregantes com variabilidade genética superior. O terceiro capítulo foi elaborado para avaliar a interação genótipos por ambientes para o caráter produtividade de grãos em genótipos de soja convencional, de ciclo precoce. Assim, os genótipos foram cultivados em 15 ambientes, distribuídos em cinco estados brasileiros, para determinar sua adaptabilidade e estabilidade por intermédio de métodos paramétricos, não paramétricos e multivariados. O método Wricke (1965), Eberhart e Russel (1966) e AMMI identificaram as linhagens UFU 21 e UFU 22 como as mais estáveis, sendo que ambas apresentaram produtividade de grãos superior a 3800,00 kg ha-1. A linhagem UFU 06 obteve média de produtividade de grãos superior a 4000,00 kg ha-1 e apresentou adaptação ampla pelos métodos Annicchiarico (1992) e Lin e Binns (1988) modificado por Carneiro (1998) e Centróide. / The study of genetic diversity and the knowledge of the relationships among improved cultivars are fundamental for soybean breeding programs, since they help the selection of breeders and recommendation of cultivars. This thesis is subdivided into three chapters, the first one deals with a theoretical reference regarding the culture, the economic importance and the improvement of soybean. The second chapter was developed with the objective of evaluating the genetic diversity from phenotypic traits, of conventional early maturity soybean genotypes in different environments, determining the importance of traits in soybean genetic divergence and selecting parents of broad genetic diversity for breeding programs, using different multivariate clustering methods. The experiment was conducted in two distinct locations, Campo Novo dos Parecis - MT, season 2010/2011 and Urutaí - GO, season 2012/2013. Ten genotypes of conventional early maturity soybean were evaluated in a randomized complete block design, in which eight agronomic characters were measured. By univariate and multivariate analyzes it was possible to conclude that the groupings formed by all the multivariate methods, with the means of the phenotypic values of the genotypes, allowed to infer about the promising combinations for artificial hybridizations. Number of days for flowering, plant height at maturity and height of insertion of the first pod were the characters that contributed the most to the genetic divergence in soybean when considering the two crop environments. UFU 106 and UFU 108 lines are the most recommended as part of the hybridizations with divergent genotypes, since they are complementary in grain yield and lower vegetative phase. Hybridizations between the following pairs of genotypes are recommended to obtain segregating populations with superior genetic variability: UFU 106 x UFU 112; UFU 106 x Emgopa 316; UFU 108 x Emgopa 316; UFU 112 x Emgopa 316. The third chapter was elaborated to evaluate the genotype interaction by environments for grain yield characteristics in conventional soybean genotypes of early maturity, grown in 15 environments distributed in five Brazilian states, to determine the adaptability and stability of the genotypes by parametric, non-parametric and multivariate methods. Wricke (1965), Eberhart and Russel (1966) and AMMI methods identified UFU 21 and UFU 22 lines as the most stable, both with grain yields higher than 3800,00 kg ha-1. The strain UFU 06 obtained an average grain yield of more than 4000,00 kg ha-1 and presented wide adaptation by Annicchiarico (1992), Lin and Binns (1988) modified by Carneiro (1998) and Centroid methods. / Tese (Doutorado)

Les invasions biologiques dans les agroécosystèmes engendrent de lourdes pertes économiques. Parmi les nombreuses espèces en cause, on retrouve les nématodes phytoparasites, vers microscopiques s’attaquant principalement aux racines. Présent dans tous les principaux pays producteurs de soya, le nématode à kyste du soya (NKS), Heterodera glycines, serait à lui seul responsable annuellement de plusieurs milliards de dollars de pertes. La rotation avec des cultivars résistants est le moyen le plus efficace de contrôler les populations de NKS, mais la surutilisation des mêmes lignées a conduit à la sélection d’individus virulents et mené à leur inefficacité. À ce jour, les mécanismes ainsi que les gènes de virulence associés au contournement de la résistance continuent de mystifier les scientifiques. Dans cette thèse, les effets des changements climatiques sur la reproduction et l’établissement du NKS ainsi que sur la phénologie de son hôte, le soya, ont été étudiés. Le premier modèle bioclimatique simulant le cycle de vie du NKS et du soya a été développé. Il a démontré que le nématode peut déjà se reproduire dans toutes les régions du Québec et que la hausse attendue des températures dans le futur proche (2041-2070) permettrait au NKS de pratiquement doubler le nombre de générations produites par saison de croissance dans toutes les régions. De plus, la production de soya issu du groupe de maturité I pourrait s’étendre à toutes les régions du Québec d’ici 2070. Une étude sur la distribution de la variabilité génétique entre 64 populations américaines et ontariennes et les gènes associés à diverses composantes bioclimatiques et leur rôle dans l’adaptation a également été réalisée. Celle-ci a révélé que la diversité génétique était très élevée entre les populations et qu’un flux de gène continu aurait facilité l’adaptation du NKS à diverses conditions bioclimatiques et son établissement dans toutes les régions nord-américaines où l’on produit du soya. Finalement, cette thèse présente l’analyse des génotypes du NKS et des gènes différentiellement exprimés sur des plants de soya résistant (Peking et PI88788) et sensible (Essex). En plus d’identifier plusieurs protéines liées à la virulence, cette étude a permis de mettre en évidence une région génomique sous forte pression évolutive. Cet îlot génique contient plusieurs répétitions en tandem qui ont divergé et dont certaines sont maintenant utilisées de façon sélective pour le contournement de différents types de résistance. / Biological invasions in agroecosystems are a major cause of economic losses. Plant parasitic nematodes are among the many species causing significant crop damages. The soybean cyst nematode (SCN) is causing billions of dollars of losses in all areas where soybean is produced. Rotation with resistant cultivars is the most effective mean of controlling SCN populations, but the overuse of the same lines has led to the selection of virulent individuals and the ineffectiveness of resistance. To this day, the virulence genes and mecanisms associated with the circumvention of resistance continue to mystify scientists. In this thesis, I explored the effects of climate change on the reproduction and establishment of SCN as well as on the phenology of its host, soybean. I have demonstrated that the nematode can already reproduce in all regions of Québec and that the expected rise in temperatures in the near future (2041-2070) will allow the development of more generations per growing season in all regions. In addition, I have demonstrated that the area suitable for the production of soybean from maturity group I will expand toward the north by 2070, further facilitating the expansion of SCN. I have also explored the genetic variability among more than 64 SCN populations from North America and analyzed the genes associated with various bioclimatic components and their role in adaptation. These analyses revealed that the genetic diversity was very high among SCN populations. This diversity associated with a continuous gene flow between populations has facilitated the adaptation of SCN to various bioclimatic conditions and its establishment in all US and Canadian soybean producing regions. Finaly, this thesis presents an analysis of the SCN genotypes and the differentially expressed genes associated with virulence in two resistant soybean lines (Peking and PI88788) and susceptible Essex. This work has identified several proteins associated with virulence and allowed the discovery of a genomic region under strong evolutionary pressure. This island contains several genes in tandem duplications that have diverged and are now used selectively for overcoming different sources of resistance.

No description available.