No description available.

Animal domestication, the process where animals become adapted to living in proximity to humans, is associated with the alteration of multiple traits, including decreased fearfulness and stress response. With an estimated population of 50 billion, the domesticated chicken is the most populous avian species in the world. Hundreds of chicken breeds have been developed for meat and egg production, hobby or research purposes. Multidirectional selection and the relaxation of natural selection in captivity have created immense phenotypic diversity amongst domesticates in a relatively short evolutionary time. The extensive phenotypic diversity, existence of the wild ancestor, and feasibility of intercrossing various breeds makes the chicken a suitable model animal for deciphering genetic determinants of complex traits such as stress response. We used chicken domestication as a model to gain insights about the mechanisms that regulate stress response in an avian species. We studied behavioural and physiological stress response in the ancestral Red Junglefowl and one of its domesticated progenies, White Leghorn. An advanced intercross between the aforementioned breeds was later used to map genetic loci underlying modification of stress response. The general pattern of the stress response in chickens was comparable with that reported in mammals, however we identified distinctive differences in the stress modulatory pathways in chickens. We showed that changes in the expression levels of several stress modulatory genes in the brain, the pituitary and the adrenal glands underlie the observed modified stress response in domesticated chickens. Using quantitative trait loci (QTL) mapping, several QTL underlying stress induced corticosterone, aldosterone and baseline dehydroepiandrosterone (DHEA) levels were detected. As a next step, we combined QTL mapping with gene expression (eQTL) mapping and narrowed two QTL down to the putative causal genes, SERPINA10 and PDE1C. Both of these genes were differentially expressed in the adrenal glands of White Leghorn and the Red Junglefowl, had overlapping eQTL with hormonal QTL, and their expression levels in the adrenal glands were correlated with plasma levels of corticosterone and al-dosterone. These two genes thus serve as strong candidates for further functional investigation concerning modification of the stress response during domestication. This dissertation increase the knowledge about genetics and physiology of the stress response in an avian species and its modification during domestication. Our findings expand the basic knowledge about the stress response in chicken, which can potentially be used to improve welfare through appropriate genetic selection.

The fundamental theme my thesis explores is the relationship between genetic variation and phenotypic variation. It addresses three main questions. What is the genetic architecture of traits in the HS? How can sequence information help identifying the sequence variants and genes responsible for phenotypic variation? Are the genetic factors contributing to phenotypic variation in the rat homologous to those contributing to variation in the same phenotype in the mouse? To address these questions, I analysed data collected by the EURATRANS consortium on 1,407 Heterogeneous Stock (HS) rats descended from eight inbred strains through sixty generations of outbreeding. The HS rats were genotyped at 803,485 SNPs and 160 measures relevant to a number of models of disease (e.g. anxiety, type 2 diabetes, multiple sclerosis) were collected. The eight founders of the Stock were genotyped and sequenced. I identified loci in the genome that contribute to phenotypic variation (Quantitative Trait Loci, QTLs), and integrated sequence information with the mapping results to identify the genetic variants underlying the QTLs. I made some important observations about the nature of genetic architecture in rats, and how this compares to mice and humans. I also showed how sequence information can be used to improve mapping resolution, and in some cases to identify causal variants. However, I report an unexpected observation: at the majority of QTLs, the genetic effect cannot be accounted for by a single variant. This finding suggests that genetic variation cannot be reduced to sequence variation. This complexity will need to be taken into account by studies that aim at unravelling the genetic basis of complex traits.

L’hypertension artérielle essentielle (HTA) est une pathologie complexe, multifactorielle et à forte composante génétique. L’impact de la variabilité dans le nombre de copies sur l’HTA est encore peu connu. Nous envisagions que des variants dans le nombre de copies (CNVs) communs pourraient augmenter ou diminuer le risque pour l’HTA. Nous avons exploré cette hypothèse en réalisant des associations pangénomiques de CNVs avec l’HTA et avec l’HTA et le diabète de type 2 (DT2), chez 21 familles du Saguenay-Lac-St-Jean (SLSJ) caractérisées par un développement précoce de l’HTA et de la dyslipidémie. Pour la réplication, nous disposions, d’une part, de 3349 sujets diabétiques de la cohorte ADVANCE sélectionnés pour des complications vasculaires. D’autre part, de 187 sujets de la cohorte Tchèque Post-MONICA (CTPM), choisis selon la présence/absence d’albuminurie et/ou de syndrome métabolique. Finalement, 134 sujets de la cohorte CARTaGENE ont été analysés pour la validation fonctionnelle. Nous avons détecté deux nouveaux loci, régions de CNVs (CNVRs) à effets quantitatifs sur 17q21.31, associés à l’hypertension et au DT2 chez les sujets SLSJ et associés à l’hypertension chez les diabétiques ADVANCE. Un modèle statistique incluant les deux variants a permis de souligner le rôle essentiel du locus CNVR1 sur l’insulino-résistance, la précocité et la durée du diabète, ainsi que sur le risque cardiovasculaire. CNVR1 régule l’expression du pseudogène LOC644172 dont le dosage est associé à la prévalence de l’HTA, du DT2 et plus particulièrement au risque cardiovasculaire et à l’âge vasculaire (P<2×10-16). Nos résultats suggèrent que les porteurs de la duplication au locus CNVR1 développent précocement une anomalie de la fonction bêta pancréatique et de l’insulino-résistance, dues à un dosage élevé de LOC644172 qui perturberait, en retour, la régulation du gène paralogue fonctionnel, MAPK8IP1. Nous avons également avons identifié six CNVRs hautement hérités et associés à l'HTA chez les sujets SLSJ. Le score des effets combinés de ces CNVRs est apparu positivement et étroitement relié à la prévalence de l’HTA (P=2×10-10) et à l’âge de diagnostic de l’HTA. Dans la population SLSJ, le score des effets combinés présente une statistique C, pour l’HTA, de 0.71 et apparaît aussi performant que le score de risque Framingham pour la prédiction de l’HTA chez les moins de 25 ans. Un seul nouveau locus de CNVR sur 19q13.12, où la délétion est associée à un risque pour l’HTA, a été confirmé chez les Caucasiens CTPM. Ce CNVR englobe le gène FFAR3. Chez la souris, il a été démontré que l’action hypotensive du propionate est en partie médiée par Ffar3, à travers une interférence entre la flore intestinale et les systèmes cardiovasculaire et rénal. Les CNVRs identifiées dans cette étude, affectent des gènes ou sont localisées dans des QTLs reliés majoritairement aux réponses inflammatoires et immunitaires, au système rénal ainsi qu’aux lésions/réparations rénales ou à la spéciation. Cette étude suggère que l’étiologie de l’HTA ou de l’HTA associée au DT2 est affectée par des effets additifs ou interactifs de CNVRs. / Essential hypertension (HT) is a multifactorial complex disease with a strong genetic component. However, little is known about the effects of copy number variance on HT. We hypothesized common Copy Number Variants (CNVs) could increase or decrease the risk for HT. We performed GWAS of CNVs with HT and, with HT and Type 2 Diabetes (T2D), in 21 families of the Saguenay-Lac-St-Jean region of Quebec (FC) affected by early-onset hypertension and dyslipidemia. Replication was tested in a cohort of 3349 unrelated diabetic subjects of Caucasian origin from the ADVANCE trial. Replication was also tested in 187 individuals from the Czech Post-Monica (CPM) cross-sectional survey, ascertained by the presence/absence of albuminuria and/or metabolic syndrome. We performed locus-specific transcriptional analyses in 134 subjects from the CARTaGENE population cohort. We identified two CNV Regions (CNVRs), at 17q21.31, associated with HT and T2D in FC and associated with hypertension in ADVANCE diabetics. A statistical model of association including both CNVRs underlined the main effect size of CNVR1 on insulin resistance, T2D early onset and duration, and risk for cardiovascular diseases (CVD). CNVR1 appeared to influence LOC644172 expression, whose transcript abundance was associated with the prevalence of HT and T2D, and strongly with the risk of CVD and vascular age (P<2×10-16). Our results suggest carriers of copy-number gain at these 17q21.31 loci, principally at the CNVR1 locus, undergo premature β-cell functional deregulation and insulin resistance, due to increase dosage of the LOC644172 pseudogene, which might in turn affect the regulation of expression of its functional paralog, MAPK8IP1. We also report six different CNVR loci, highly heritable and contributing to the risk of hypertension, in French Canadians. The combined CNV risk score appeared robustly related to prevalence of hypertension (p=2×10-10) and age at diagnosis of hypertension. In FC, this combined CNV risk score model showed a C-statistic of 0.71 for HT and appeared as powerful as Framingham HT risk score in predicting hypertension in individuals aged less than 25. We validated the association of a new locus, 19q13.12 deletion-CNVR, with hypertension, in CPM. FFAR3 surrounds this 19q13.12 deletion-CNVR. It has been demonstrated that in mice, a portion of propionate hypotensive effect is mediated by Ffar3, and involves a cross-talk between the gut microbiota and the renal-cardiovascular system. The identified CNVRs appear to influence genes and QTLs mainly related to immune and inflammatory responses and renal damaged and repair. Some CNVRs are exclusive to primates. This study suggests that additive and interactive actions of multiple copy-number variants are involved in the etiology of hypertension or of hypertension associated with T2D.

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

Aujourd'hui, alors que le nombre de marqueurs génétiques disponibles augmente rapidement, de nouvelles populations doivent être créées pour exploiter au mieux cette quantité d'informations dans le but de mieux comprendre l'architecture génétique de caractères complexes. Les populations de type MAGIC ont été créées pour rassembler les avantages des populations bi-parentales et des panels d'associations, la bonne puissance de détection et une localisation précise. L'objectif de cette thèse était d'étudier l'intérêt de la population MAGIC INRA pour l'analyse de l'architecture génétique de la précocité de floraison. Cette population a été créée à partir de 60 parents brassés durant 12 générations de panmixie grâce à l'introduction d'un gène de stérilité mâle (ms1b). Cette étude a été réalisée sur 56 parents toujours disponibles en banque de graines et 380 lignées dérivées de la population après les 12 générations de recombinaison. Cette population a été génotypée avec la puce 9K iSelect, représentant environ 5 000 SNPs localisés sur tout le génome, additionnée de 14 marqueurs localisés dans des gènes candidats. Ce jeu de données moléculaires a été complété par des données fines de phénotypage de la précocité de floraison. Suite aux 12 générations de panmixie, le DL de cette population a été très réduit, à longue comme à moyenne distance (<10cM). Ce faible DL nous a amené à développer un algorithme basé uniquement sur le DL qui ordonne les marqueurs de manière à avoir un DL décroissant monotone avec la distance. L'algorithme ordonne globalement de la même manière que la carte génétique les marqueurs à longue distance mais à courte distance le DL est moins lié à la distance génétique. La différence réside sur l'équilibre entre les effets de la recombinaison et de la dérive génétique sur le DL. L'intérêt de la population MAGIC INRA pour détecter des QTLs a ensuite été étudié avec deux approches : une approche évolutionniste et une approche de génétique d'association. La première approche détecte les loci soumis à sélection par comparaison des fréquences alléliques de la population initiale (G0) et de la population évoluée (G12) grâce à une nouvelle méthode. La population initiale est composée des parents pondérés par une contribution estimée avec une nouvelle méthode bayésienne. 26 régions génomiques soumises à sélection ont été détectées. Une analyse de génétique d'association avec les marqueurs détectés sous sélection a montré que respectivement cinq et trois zones étaient associées à la précocité avec un semis d'automne et au caractère printemps/hiver. Une analyse phénotypique a effectivement mis en évidence la précocification de la date de floraison et une augmentation de la proportion de plantes de type printemps. Une analyse de génétique d'association a ensuite été réalisée sur les lignées SSD sur 12 caractères x environnements i.e. la date d'épiaison et le temps de remplissage du grain mesurés dans six environnements. Les tests d'association ont aussi été réalisés avec des variables synthétisant l'information présente dans plusieurs traits phénotypiques soit avec une ACP, soit avec un modèle écophysiologique. Au total, toutes ces analyses ont détecté six QTLs dont trois correspondants à des gènes majeurs. Parmi ces six QTLs, deux sont spécifiques des caractères mesurés avec un semis d'automne et deux avec ceux mesurés avec un semis de printemps. / Nowadays, with the dramatically increase of available molecular markers, there is a deep need for new populations allowing to exploit all of this information to better understand the genetic architecture of complex traits. MAGIC populations as they are built to bring together bi-parental populations and association panel advantages, provide such powerful detection and fine mapping capacities. The aim of these PhD was to study the MAGIC INRA population usefulness for the study of genetic architecture of earliness. This population is derived from 12 cycles of random crosses between 60 founders, turning wheat from selfing to outcrossing thanks to the use of a nuclear male sterility gene (ms1b, Probus donor). This population is composed of 56 parents still available and 380 SSD lines. Parents and SSD lines were genotyped using the 9K iSelect SNPs array, providing around 5 000 SNPs on the whole genome, as well as 14 addition markers located in candidate genes. They were also finely phenotyped for earliness traits. With the 12 panmictic generations, the population LD decreased strongly, especially at long and medium distance (<10cM). This allowed us to develop an algorithm mapping markers on the sole pairwise LD information, ordering markers in a way to have the LD decreasing along the distance. When considering long distances, overall the results were consistent with the order found on genetic maps while at short distance LD was poorly linked to genetic distance. These differences between long and short distances were linked to the balance between recombination and drift effects on LD. The usefulness of the MAGIC INRA population for QTL detection was analyzed with two approaches: an evolutionary approach and an association genetics approach. The first one detects loci under selection by identifying high shift in allelic frequency with a new method. The initial population was composed of founders weighted by a contribution estimated with a new Bayesian method. 26 genomic areas under selection were detected. An association genetics analysis with the markers detected as under selection showed respectively five and three genomic regions associated with earliness and growth habit. Actually the G12 population was found phenotypically earlier than the G0 and with more spring individuals. A broader association genetics analysis was performed on G12 population, studying 12 traits x environments i.e. heading date and grain filling time, both observed in six environmental conditions. Two additional integrated traits from either PCA or ecophysiological model were also analyzed. In all, these different analyses detected six QTLs, three of them corresponding to candidate genes. Among these six QTLs, two were specific to autumn sowing and two specific to spring sowing.

No description available.

A cultura da cana-de-açúcar está exposta a diversos patógenos, entre eles, o fungo Sporisorium scitamineum, agente causal do carvão, que causa perdas significativas na produção e na qualidade do caldo. O uso de genótipos resistentes é o principal método de controle da doença, o que torna essencial o conhecimento das bases genéticas da resistência, favorecendo a seleção de genótipos superiores. Neste estudo, uma população F1 segregante, derivada do cruzamento entre \'IAC66-6\' e \'TUC71-7\', foi genotipada usando marcadores EST-SSR e TRAP, os quais foram alocados em um mapa prévio, visando identificar marcadores associados a locos quantitativos de resistência a esse patógeno. A incidência de carvão foi avaliada em dois ensaios realizados nos anos de 2009 e 2010, em delineamento experimental inteiramente casualizado. O principal sintoma do carvão (número de chicotes) foi tomado ao longo dos ensaios e os dados foram utilizados para o cálculo da área sob a curva de progresso da doença (AUDPC), sendo os valores de AUDPC normalizados e analisados por meio de modelos mistos. O mapeamento de locos quantitativos (QTL) seguiu a abordagem de mapeamento por intervalo composto (CIM). O mapa aqui construído contém 721 marcadores, compilando EST-SSRs, TRAPs, além de AFLPs e marcadores direcionados ao retrotransposon scIvana_1 já alocados no mapa prévio. Estes foram posicionados em 124 grupos de co-segregação, sendo 65 deles atribuídos em dez grupos de homo(eo)logia, com base em locos EST-SSR em comum. O mapa totaliza 6.223,0 cM e tem uma densidade média de um marcador a cada 8,6 cM. O uso da metodologia CIM permitiu detectar oito locos quantitativos associados à resistência de S. scitamineum, sendo quatro deles identificados na primeira avaliação, dois novos locos na segunda avaliação e dois considerando-se o comportamento médio dos genótipos nos dois anos de avaliação. Observou-se a predominância de alelos com efeitos aditivos de resistência, comparativamente aos efeitos de dominância, sendo seis deles relacionados à diminuição da suscetibilidade e quatro com o aumento. Dentre os QTL, cinco segregaram na proporção 1:1, dois 3:1 e um na proporção de 1:2:1. Os QTLs foram capazes de explicar individualmente de 3,4% a 5,7% da variação fenotípica. O QTL que explicou a maior porcentagem da variação, detectado na primeira avaliação (5,7%), foi posicionado a 5,0 cM de outro QTL considerando-se o comportamento médio dos genótipos, sugerindo que estes QTLs localizam-se na mesma região genômica. Interessantemente, um dos QTLs está posicionado em um intervalo que contém uma marca TRAP e outra ancorada no retrotransposon scIvana. Espera-se que esses resultados contribuam para estudos futuros sobre genes candidatos envolvidos na resistência, o papel dos retrotransposons na resposta da planta a patógenos, bem como possam dar subsídios a programas de seleção assistida por marcadores. / The sugarcane is exposed to several pathogens, including the fungus Sporisorium scitamineum, the smut disease´s causal agent, which causes significant losses in yield and juice quality. The use of resistant genotypes is the main strategy to control the disease, therefore it is essential the knowledge on the genetic basis of resistance for selecting superior genotypes. In this study, a F1 segregating population derived from a cross between \'IAC66-6\' and \'TUC71-7\' were genotyped using EST-SSR and TRAP markers that were placed on a prior map aiming at to identify markers associated to the smut resistance genes. The incidence of smut was evaluated in two trials performed in 2009 and 2010 in a completely randomized design. The main smut symptom (number of whips) was recorded in both trials, and data were used to calculate the area under the disease-progression curve (AUDPC). The values were normalized and analyzed using mixed models. The mapping of quantitative loci (QTL) followed the composite interval mapping (CIM) method. The map here in constructed contains 721 single dose markers compiling EST-SSRs, TRAPs as well as AFLPs and markers anchored in the retrotransposon scIvana_1, both previously allocated. Markers were positioned on 124 co-segregation groups, and 65 of them were assigned to ten groups of homo(eo)logy, based on common EST-SSR loci. The map totalized 6223.0 cM with a marker density of one marker every 8.6 cM. The use of CIM methodology allowed the detection of eight loci associated with quantitative resistance to S. scitamineum, four being identified in the first trial, two new QTLs in the second trial, and two considering the average genotype behavior in both years of evaluation. There was predominance of additive effects in comparison to the dominance effects, six of them related to decreased susceptibility and four related to increased susceptibility. Out of the QTLs, five segregated in a 1:1 ratio, two in a 3:1 ratio, and two in a 1:2:1 ratio. QTLs were able to explain individually 3.4% to 5.7% of the phenotypic variation. The QTL that explained the largest percentage of the variation, detected in the first trial (5.7%) was located at a distance of 5.0 cM from other QTL detected when considering the genotype average behavior, suggesting that these QTLs are positioned in the same genomic region. Interestingly, one QTL was located in an interval that contains a TRAP marker and a scIvana_1-anchored marker. We expect that our results contribute to future studies on disease resistance candidate genes, the role of retrotransposon in plant responses to pathogens, as well as to add marker-assisted selection programs.

Estudar a arquitetura genética de uma dada característica quantitativa significa descrever os fatores genéticos e ambientais que a afetam, bem como o valor dos efeitos genéticos de cada loco e suas interações. O presente trabalho teve por objetivo geral estudar a arquitetura genética de características quantitativas associadas ao desempenho e ao rendimento de carcaça de uma população experimental oriunda do cruzamento entre uma linhagem de postura (CC) e uma de corte (TT) genotipada para marcadores microssatélites que foram associados ao peso vivo aos 42 dias na população recíproca TCTC nos cromossomos 1, 3 e 4. Para tanto, foram propostos três objetivos específicos: 1) caracterizar genotipicamente as duas populações referências (TCTC e CTCT); 2) construir mapas de ligação para a população CTCT; 3) mapear QTLs associados ao desempenho e ao rendimento de carcaça na população CTCT, utilizando o Mapeamento por Intervalo Composto (CIM). Os resultados evidenciaram que as duas linhagens parentais (CC e TT) possibilitaram a criação de gerações recíprocas F1 com elevados valores do conteúdo de informação polimórfica e heterozigosidade observada, resultado do satisfatório número de alelos verificado. Isto implica que as populações recíprocas F2, derivadas de ambas as gerações F1, são apropriadas para mapear QTLs associados ao desempenho e ao rendimento de carcaça. Adicionalmente, os mapas de ligação da população CTCT são similares ao de sua população recíproca TCTC e ao Mapa Consenso da galinha doméstica. A estimação de intervalos de confiança para as distâncias entre locos permitiu melhor entendimento das diferenças obtidas tanto no tamanho dos cromossomos quanto na ordem dos locos. Finalmente, foram observadas vantagens com o uso do CIM nas estimativas de número de QTLs mapeados e em suas posições. As regiões onde os QTLs foram mapeados neste estudo corroboram algumas daquelas da população recíproca TCTC, mas por outro lado sugerem que outras regiões do genoma dos cromossomos 1, 3 e 4 podem controlar tais características. Foram definidas duas regiões ainda não descritas na literatura no cromossomo 4: uma associada ao ganho de peso (MCW0240- LEI0063) e outra ao consumo de ração (LEI0085-MCW0174) 35-41 dias. Os resultados deste estudo podem ser explorados através do mapeamento fino, buscas in silico por genes candidatos por posição e validação em populações comerciais, a fim de implementar a seleção assistida por marcadores em programas de melhoramento genético avícolas. / Understanding the genetic architecture means to describe the genetic and environment factors that affect a quantitative trait, together with the estimation of individual genetic effects and its interactions. The aim of this work was to understand the genetic architecture of quantitative traits associated with performance and carcass yield of a chicken reference population created from crosses between a layer line (CC) and a broiler line (TT) genotyped for microsatellite markers that were associated with body weight at 42 days in its reciprocal cross on chromosomes 1, 3 and 4. Three specific topics were presented: 1) to characterize genotypically two reference populations (TCTC and CTCT); 2) to construct linkage maps in the CTCT population and 3) to map QTL associated with performance and carcass yield in CTCT population, using Composite Interval Mapping (CIM). The results showed that the two parental lines (CC and TT) created reciprocal F1 generations with suitable polymorphic information content values and observed heterozygosity, as result of the satisfactory number of alleles. This implies that the reciprocal F2 populations, derived from both F1 generations, are appropriated to map QTL associated with performance and carcass yield. The linkage maps from CTCT population were similar to its reciprocal population and to the Chicken Consensus Linkage Map. Estimating confidence intervals for distances between loci allowed the elucidation of the causes for differences both on chromosome sizes and on order loci. Finally, there were advantages in using CIM, mainly on QTL number and location. The regions where QTLs were mapped in this study not only corroborated some results from TCTC reciprocal population, but also suggested that other genome regions on chromosomes 1, 3 and 4 may control such traits. On chromosome 4 two regions were defined that were not previously described in the literature: one associated with weight gain (MCW0240-LEI0063) and another one with feed intake (LEI0085-MCW0174) at 35- 41 days. The results of this study can be explored through fine mapping, searches in silico for candidate genes and by validation in commercial populations, in order to implement marker assisted selection in poultry breeding programs.

Soja (Glycine max (L.) Merrill) é uma das mais importantes oleaginosas no mundo e sua relevância pode ser também mensurada pela extensão da sua produção no Brasil, onde representa quase a metade do total da área plantada com grãos. A importância da soja está também associada à multiplicidade de utilização do grão, como por exemplo, na alimentação humana e animal, na indústria química e na geração de energia como biodiesel. A produtividade da soja tem sido frequentemente impactada devido ao ataque de pragas e doenças. Dentre as espécies de fitonematoides, o nematoide-das-lesões-radiculares (Pratylenchus brachyurus Godfrey), tem gerado significativas perdas econômicas aos produtores, variando entre 30 a 50%, dependendo da infestação da cultura. Este trabalho teve como objetivo identificar QTLs (Quantitative Trait Loci), a partir de um conjunto de fenótipos associados à resistência ao nematoide-das-lesões-radiculares utilizando a abordagem de mapeamento multivariado. Uma população de 174 indivíduos F2, obtidos a partir do cruzamento entre duas linhagens de soja FTPG06A e FTPG12X (com baixo fator de reprodução do nematoide), foi utilizada para a obtenção dos valores genéticos preditos (BLUPs - Best Linear Unbiased Predictions) de cinco características estudadas e também para a genotipagem com o SoySNP6k Bead Chip. As características avaliadas foram: fator de reprodução (FR), peso fresco (PA) e comprimento (CA) da parte aérea, peso fresco (PR) e comprimento (CR) da raiz. Um total de 1.240 marcadores SNP (Single Nucleotide Polymorphism) foram mapeados nos 20 grupos de ligação (GLs) da soja. O comprimento total do mapa foi de 3.084,46 centiMorgans (cM), com intervalo médio de 2,54 cM entre marcadores adjacentes. A identificação de QTLs (Quantitative Trait Loci) para os caracteres fenotípicos foi realizada utilizando-se o mapeamento de intervalos múltiplos univariado (MIM) e multivariado (MT-MIM), com estimativa dos efeitos principais dos QTLs e análises de epistasia envolvendo pares de QTLs. Na abordagem MIM foram identificados três QTLs associados à variável CR, nos GLs (Grupos de Ligação) A2 e E (2 QTLs), explicando um total de 34,22% da variação fenotípica dessa variável para a população em estudo. Na abordagem MT-MIM, foram selecionados dois conjuntos de variáveis, de acordo com a correlação entre as mesmas. Três regiões genômicas foram reveladas, sendo estatisticamente significativas para as variáveis CR, FR e CA. A comparação dos seis QTLs identificados no presente estudo com o banco de dados de QTLs do Soybase forneceu evidências de que cinco QTLs, ainda não foram descritos na literatura. Uma busca por sequências candidatas em duas regiões de interesse, associadas à variável FR, foi realizada, com base na plataforma de dados genômicos PlantGDB. Várias sequências candidatas indicam relação com mecanismos importantes na resposta das plantas a estresses bióticos. Dessa forma, os resultados obtidos no presente estudo forneceram informações para auxiliar na melhor compreensão da arquitetura genética dos caracteres quantitativos analisados. / Soybean (Glycine max (L.) Merrill) is one of the most important oil crop worldwide and its relevance can also be measured by the extension of soybean grain production in Brazil, where it represents almost half of the total planting area with grains crops. Importance of soybean is also related to a multiplicity of usage of the grain, for example, in human consumption, animal feed, chemical industry and for energy generation as biofuel. Soybean yield has been frequently reduced by occurrence of pest and diseases. Among phytonematodes species, root lesion nematode (Pratylenchus brachyurus Godfrey) has caused significant economic losses to farmers, ranging from 30 to 50%, depending on crop infestation. This research aimed to identify QTLs (Quantitative Trait Loci), from a set of phenotypes associated with resistance to root lesion nematode, using the multivariate multiple interval mapping. A mapping population of 174 F2 plants derived from a by-parental cross between two soybean breeding lines FTPG06A and FTPG12X (with low nematode reproduction factor), was used for prediction of genetic values (BLUPs - Best Linear Unbiased Predictions) for five traits studied and also for genotyping with SoySNP6k Bead Chip. Traits evaluated were reproduction factor (FR), shoot weight (PA), shoot length (CA), root weight (PR) and root length (CR). A total of 1,240 SNP (Single Nucleotide Polymorphism) markers were mapped into 20 soybean linkage groups (LG). A total map length was 3,084.46 centiMorgans (cM) with an average of 2.54 cM between flanking markers. QTL mapping for those traits was performed using univariate (MIM) and multivariate (MT-MIM) multiple-interval mapping, with main QTL effects estimates and epistasis analysis between QTL pairs. MIM analysis identified three QTLs associated to CR trait at LG A2 and LG E (2 QTL), explaining 34,22% of phenotypic variation estimated for this mapping population. For MT-MIM analysis, two sets of traits were selected, according to the correlation among them. Three genomic regions statistically significant for CR, FR and CA traits were identified. Comparison between six identified QTL and QTL database at Soybase provided evidence that five QTL have not been published yet. Search for candidate sequences located in two regions associated with FR trait were further performed on the PlantGDB genomic data platform. Several candidate sequences indicate relationships with important plant response mechanisms to biotic stresses. Thus, results obtained in the present study provided information to improve knowledge of the genetic architecture of the analyzed quantitative traits.