Groat oil content and composition are important quality traits in oats (Avena sativa L). These traits are controlled by many genes with additive effects. The chromosomal regions containing these genes, known as quantitative trait loci (QTL), can be discovered through their close association with markers. This study investigated total oil content and fatty acid components in an oat breeding population derived from a cross between high oil ('Dal') and low oil ('Exeter') parents. A genetic map consisting of 475 DArT (Diversity Array Technology) markers spanning 1271.8 cM across 40 linkage groups was constructed. QTL analysis for groat oil content and composition was conducted using grain samples grown at Aberdeen, ID in 1997. QTL analysis for multiple agronomic traits was also conducted using data collected from hill plots and field plots in Ottawa, ON in 2010. QTLs for oil content, palmitic acid (16:0), stearic acid (18:0), oleic acid (18:1), linoleic acid (18:2) and linolenic acid (18:3) were identified. Two of the QTLs associated with oil content were also associated with all of the fatty acids examined in this study, and most oil-related QTL showed similar patterns of effect on the fatty acid profile. These results suggest the presence of pleiotropic effects on oil-related traits through influences at specific nodes of the oil synthesis pathway. In addition, 12 QTL-associated markers (likely representing nine unique regions) were associated with plant height, heading date, lodging, and protein content. The results of this study will provide information for molecular breeding as well as insight into the genetic mechanisms controlling oil biosynthesis in oat.

Estudos genético quantitativos e moleculares são fundamentais para o melhoramento animal e sua realização com a raça Nelore é de grande importância devido a ampla participação dessa no rebanho de corte nacional. A estimação constante dos parâmetros genéticos das características de produção é necessário para a adequada condução do processo de seleção dos animais. A melhoria de características relacionadas à carcaça bovina é essencial para a eficiência e sustentabilidade da atividade e a implementação de métodos de seleção animal baseados em informações moleculares pode revolucionar a produção zootécnica e deve ser profundamente estudado. Sendo assim, os objetivos do presente estudo foram estimar parâmetros genéticos e componentes de variância através de diferentes modelos matemáticos para um total de 14 características fenotípicas (o peso ao nascimento, peso a desmama, peso ao sobreano, ganho de peso entre a desmama e o sobreano ajustado para um intervalo de 345 dias, perímetro escrotal ao sobreano, altura de garupa ao sobreano, escores visuais avaliados ao sobreano de conformação, precocidade, musculosidade, comprimento de umbigo e ossatura, e ainda características de carcaça mensuradas por ultrassonografia realizada após 30 a 45 dias de confinamento como a área de olho de lombo, espessura de gordura subcutânea, espessura de gordura na picanha). Foram estimadas correlações entre todas estas características com as de carcaça mensuradas por ultrassonografia. Sob o enfoque molecular, desenvolveu-se um programa para imputação de genótipos faltantes e estudaram-se diferentes métodos de associação de marcadores moleculares do tipo mutação de base nitrogenada única (SNP) a características de produção incluídas no índice de seleção de um programa de melhoramento da raça Nelore, utilizando inferência bayesiana. Todas as características estudadas podem ser selecionadas esperando-se progresso genético na população. Os efeitos maternos foram importantes em algumas características onde normalmente estes efeitos não têm sido considerados atualmente. A quantidade de escores atribuídos a uma característica categórica assim como o número de observações fenotípicas resultam em diferenças nas estimativas quando avaliadas por modelos lineares ou de limiar. Não deverão ser obtidos resultados satisfatórios na melhoria das características de carcaça se a seleção for baseada nas tradicionais avaliações visuais utilizadas no momento. Os métodos utilizados na análise de associação dos marcadores podem originar diferentes resultados. Os marcadores que apresentaram efeitos altamente relevantes (P<0,01) geralmente apresentaram resultados semelhantes, independentemente do método utilizado. Certos marcadores podem ter efeitos positivos para algumas características componentes do índice de seleção e negativos para as demais. A análise em conjunto com todos os SNP\'s e todos os dados fenotípicos disponíveis é viável e parece ser a mais adequada. O método desenvolvido de imputação de genótipos faltantes a partir do parentesco de animais genotipados foi eficiente. / Quantitative and molecular genetic studies are very important for animal breeding and studies with Nellore cattle have great importance due to the large participation of that breed in the Brazilian beef cattle industry (around 80% of the herd). The constant estimation of genetic parameters for traits linked to production is necessary for properly perform selection of animals. The improvement of carcass traits is essential for efficiency and profitability of the activity. The implementation of methods for animal selection based on molecular information could revolutionize animal production and should be deeply studied. Thus, the objectives of this study were to estimate genetic parameters and variance components using different mathematical models for a total of 14 traits, such as birth weight, weaning weight, yearling weight, post-weaning weight gain between weaning and yearling adjusted for 345 days, yearling scrotal circumference, yearling hip height, yearling visual scores like conformation, finishing, muscularity, bone structure and navel length. Ultrasound measurements for carcass traits performed at feedlot (30 to 45 days, at approximate age of 20 months) such as rib-eye area, fat thickness, rump fat thickness were, also, evaluated. Estimate correlations between all these traits with the carcass traits measured by ultrasound were estimated. As concerned to molecular study, an algorithm for imputation of missing genotypes was developed and different methods to analyze molecular marker (single nucleotide polymorphism - SNP) association with traits components of the selection index of a breeding program that is applied to the population studied, using bayesian inference, were used. Genetic progress will be expected for selection of all the traits studied. Maternal effects were important in some traits in which those effects are not usually considered. The amount of scores assigned to a categorical trait and the number of observations could result in different estimates when evaluated by linear or threshold models. The selection for visual scores traditionally used in that population will not improve carcass traits. The methods used to analyze the association of markers may lead to different results. The SNP\'s with association effects of high relevance (P<0.01) generally express their effects regardless of the method used to analyze. Some markers may have positive effects for some traits of selection index, but negative for others. The joint analysis with all SNPs and with all available phenotypes is feasible and appears to be more appropriate. The algorithm developed for imputation of missing genotypes from pedigree information of genotyped animals was efficient.

Understanding complex traits is a fundamental challenge in plant genetics and a prerequisite for molecular breeding. Tools for trait dissection are markers, maps, and quantitative trait locus (QTL) analysis. Marker-assisted selection (MAS) is an application that integrates these tools. In this thesis research, a new sequence-based marker was evaluated, maps were constructed and used, and QTLs were detected using two types of populations. Marker-assisted selection was used to develop a novel class of barley. Restriction-site Associated DNA (RAD), a sequence based-marker technology, allows for simultaneous high-density single nucleotide polymorphism (SNP) discovery and genotyping. We assessed the value of RAD markers for linkage map construction using the Oregon Wolfe Barley (OWB) mapping population. We compared a RAD-based map to a map generated using Illumina GoldenGate Assay (EST-based SNPs). The RAD markers generated a high quality map with complete genome coverage. We then used the RAD map to locate QTL for agronomic fitness traits. A paper describing this research was published (Chutimanitsakun et al., 2011). Marker-assisted selection was used to rapidly develop fall-sown barley germplasm for human food uses. The target traits were high grain β-glucan, vernalization sensitivity (VS) and low temperature tolerance (LTT). The target loci were WX and VRN-H2. Marker-assisted selection was effective in fixing target alleles at both loci and waxy starch led to increase in grain β-glucan. Unexpected segregation at VRN-H1 and VRN-H3, revealed by genome-wide association mapping (GW-AM), led to unanticipated phenotypic variation in VS and LTT. We found that GW-AM is an efficient and powerful method for identifying the genome coordinates of genes determining target traits. Precise information is obtained with perfect markers; additional research may be needed when multiple alleles are segregating at target loci and significant associations are with markers in linkage disequilibrium (LD) with the target loci. A paper describing this research will be submitted for publication. / Graduation date: 2012

Groat oil content and composition are important quality traits in oats (Avena sativa L). These traits are controlled by many genes with additive effects. The chromosomal regions containing these genes, known as quantitative trait loci (QTL), can be discovered through their close association with markers. This study investigated total oil content and fatty acid components in an oat breeding population derived from a cross between high oil ('Dal') and low oil ('Exeter') parents. A genetic map consisting of 475 DArT (Diversity Array Technology) markers spanning 1271.8 cM across 40 linkage groups was constructed. QTL analysis for groat oil content and composition was conducted using grain samples grown at Aberdeen, ID in 1997. QTL analysis for multiple agronomic traits was also conducted using data collected from hill plots and field plots in Ottawa, ON in 2010. QTLs for oil content, palmitic acid (16:0), stearic acid (18:0), oleic acid (18:1), linoleic acid (18:2) and linolenic acid (18:3) were identified. Two of the QTLs associated with oil content were also associated with all of the fatty acids examined in this study, and most oil-related QTL showed similar patterns of effect on the fatty acid profile. These results suggest the presence of pleiotropic effects on oil-related traits through influences at specific nodes of the oil synthesis pathway. In addition, 12 QTL-associated markers (likely representing nine unique regions) were associated with plant height, heading date, lodging, and protein content. The results of this study will provide information for molecular breeding as well as insight into the genetic mechanisms controlling oil biosynthesis in oat.

No description available.

Mapping quantitative trait loci (QTL) for traits under consideration for genetic improvement is becoming more common for many aquatic species, including Atlantic salmon. The objective of the study was to map QTL associated with length, weight, shape, parr mark number and contrast in three F2 hybrid families of European and North American strains of Atlantic salmon using single nucleotide polymorphisms. GridQTL software was used to perform separate analyses for male and female linkage maps. Numerous highly significant QTL were detected for every trait. Locations of QTL differed based on age and map used. Some QTL locations for the analyzed traits were similar to those of other studies on purebred and backcross Atlantic salmon populations; however, many more QTL were detected in the hybrid F2’s. The amount of genetic variation in skin colour and pattern displayed within the transAtlantic F2 families greatly exceeded the ranges seen in nature. / NSERC Strategic Grant

Thesis (MSc (Genetics))--University of Stellenbosch, 2010. / Includes bibliography. / ENGLISH ABSTRACT: Wheat rust is a significant contributor to the total impact of diseases on sustainable wheat production. Genetic resistance, produced by using resistance genes from wheat and other related wild species, is the simplest and most cost-effective way to guard against these diseases. The pyramiding of resistance genes in a single line is a vital practice in bringing about durable resistance. This study aimed to develop a series of doubled haploid (DH) wheat lines containing combination's of wild species genes for rust resistance. Rust resistance genes Lr19 (7BL), Sr31/Lr26/Yr9/Pm8 (1BS) and Lr54/Yr37 (2DL) were combined by means of crossing. Breeders. lines which have complex resistance including Lr24/Sr24 (3DL), Lr34/Yr18 (7D), Sr36 (2BS) and Sr2 (3BS), were used. Marker assisted selection (MAS) was used to type populations for the above mentioned genes. Using the DH method (maize pollination technique), an inbred population was developed from the selected lines, after which the lines were characterised molecularly for the resistance gene translocations which they contain. The study produced 27 lines with diverse genetic profiles. Seven lines contain four translocations (Lr24/Sr24, Lr34/Yr18, Sr2 and Lr19 or Sr31) each, 11 lines contain three genes each, six lines contain two genes each and only three lines contain a single translocation (Lr24/Sr24). The reality that rust pathogens have already overcome three of the resistance genes in the final population . Lr19, Sr31 and Sr24 . is a clear indication of the value of using non-major gene resistance for bringing about durable resistance. The focus should fall ever more greatly upon the application of quantitative trait loci (QTL) for this purpose, which will result in MAS contributing to the development of more durable resistance. The value of the integration of MAS and DH in combination with conventional breeding practices in breeding programmes has already been illustrated internationally for increasing the rate of cultivar development and this is reaffirmed by this study. / AFRIKAANSE OPSOMMING: Koringroes lewer jaarliks .n beduidende bydrae tot die totale impak van siektes wat volhoubare koringverbouing belemmer. Die mees eenvoudige en koste-effektiewe verweer teen hierdie siektes is genetiese weerstand, wat deur weerstandsgene vanaf koring, sowel as wilde verwante spesies, bewerkstellig word. Die stapeling van weerstandsgene in .n enkele lyn word as .n onontbeerlike praktyk om duursame weerstand tot stand te bring, geag. Hierdie studie het ten doel gehad om .n reeks verdubbelde haploiede (VH) koringlyne te ontwikkel wat kombinasies van wilde spesie gene vir roesweerstand bevat. Roesweerstandsgene Lr19 (7BL), Sr31/Lr26/Yr9/Pm8 (1BS) en Lr54/Yr37 (2DL) is deur middel van kruisings gekombineer. Telerslyne wat oor komplekse weerstand beskik wat Lr24/Sr24 (3DL), Lr34/Yr18 (7D), Sr36 (2BS) en Sr2 (3BS) insluit, is gebruik. Merker-bemiddelde seleksie (MBS) is gebruik om populasies vir bogenoemde gene te tipeer. .n Ingeteelde populasie is vanaf die geselekteerde lyne met behulp van die VH metode (mielie-bestuiwing tegniek) ontwikkel, waarna die lyne molekuler vir die weerstandsgeentranslokasies waaroor hul beskik, gekarakteriseer is. Die studie het 27 lyne met diverse genetiese profiele opgelewer. Sewe lyne bevat vier weerstandsgeentranslokasies (Lr24/Sr24, Lr34/Yr18, Sr2 en Lr19 of Sr31) elk, 11 lyne beskik oor kombinasies van drie gene elk, ses bevat twee gene elk en slegs drie lyne beskik oor .n enkele translokasie (Lr24/Sr24). Die realiteit dat die roespatogene reeds drie van die weerstandsgene in die finale populasie . Lr19, Sr31 en Sr24 . oorkom het, benadruk die waarde van die gebruik van nie-hoofgeenweerstand vir die daarstelling van duursame weerstand. Die fokus behoort toenemend meer op die aanwending van kwantitatiewe kenmerk-loci (QTL) vir hierdie doel te val en sal sodoende teweegbring dat MBS bydra tot die ontwikkeling van meer duursame weerstand. Die waarde van die integrasie van MBS en VH in kombinasie met konvensionele telingsmetodiek is reeds internasionaal vir die versnelling van kultivarontwikkeling aangetoon en word ook deur hierdie studie herbevestig.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2018-11-27T11:35:22Z No. of bitstreams: 2 Tese - Renata Cristina Alvares - 2015.pdf: 6545735 bytes, checksum: 57eee901abeda481f65a8b76157955fc (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-11-27T12:04:54Z (GMT) No. of bitstreams: 2 Tese - Renata Cristina Alvares - 2015.pdf: 6545735 bytes, checksum: 57eee901abeda481f65a8b76157955fc (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-11-27T12:04:54Z (GMT). No. of bitstreams: 2 Tese - Renata Cristina Alvares - 2015.pdf: 6545735 bytes, checksum: 57eee901abeda481f65a8b76157955fc (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2015-03-31 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The breeding of common bean cultivars with Carioca grain, slow grain darken-ing, upright plant architecture, and high yield has become a growing challenge. Slow grain darkening will increase the storage time, providing flexibility for producers for the time of sale, and consequently increasing profitability. Studies have demonstrated the existence of genetic variability for this trait, allowing the selection of lines with slow grain darkening. The objectives of this study were i) to estimate genetic and phenotypic parameters of lines of four segregating common bean populations; ii) select those with slow grain darkening, upright plant architecture and high yield; iii) seek an association between slow darkening and cooking time of grains after storage; iv) evaluate two induction methods of grain dark-ening and v) validate the markers Pvsd-1158 and PVM02TC116, associated with grain darkening. The tested lines were derived from four segregating populations resulting from crosses between the cultivar BRSMG Madrepérola with slow grain darkening and the par-ents BRS Estilo, BRS Cometa, BRS Notável, and CNFC 10429. Three trials were installed with 220 lines (55 per population), and 5 parents in a 5x15 triple lattice design, with plots of two 3-m rows, at three locations. The experiments were conducted in the winter grow-ing season 2012, one in Santo Antônio de Goiás and two in Brasilia. The traits grain yield, plant architecture, grain darkening, 100-grain weight, and cooking time were evaluated. The variance components and genetic and phenotypic parameters were estimated, and the phenotypic, genetic and environmental correlation coefficients between grain darkening and cooking time, 90 and 180 days after harvest. Induction methods of accelerated and slow darkening were compared. From the markers Pvsd- 1158 and PVM02TC116, identi-fied as previously linked to the gene that controls grain darkening, the frequency of recom-bination and selection efficiency of the markers was estimated for each population and environment and in the mean of the environments. For slow grain darkening, the estimates of heritability, genetic variance and expected gain with selection were high, indicating good chances of successful selection. For yield, plant architecture and commercial grain size, the estimates of heritability and genetic variance were high, but indicated no high gains with simultaneous selection. Lines with slow grain darkening were obtained from the four populations; the highest number of lines that combined slow darkening with upright plant architecture, high yield, and commercial grain size were derived from the crosses BRSMG Madrepérola x BRS Estilo and BRSMG Madrepérola x BRS Cometa. No im-portant genetic correlation between grain darkening and cooking time was identified, there-fore, light-colored grains do not indicate a short cooking time. The induction methods of slow and accelerated darkening, provide similar information in the discrimination of lines with slow and regular darkening. The estimates of the recombination frequency for marker Pvsd-1158 were always low, indicating the close linkage of this marker to the gene that controls slow darkening, and were stable in the different environments and populations. Marker PVM02TC116 however was not polymorphic in three of the four populations. The recombination frequency of this marker in the polymorphic population was high, showing that it is unsuitable for marker-assisted selection for grain darkening. / A obtenção de cultivares de feijoeiro-comum de grãos carioca que associem escurecimento lento dos grãos, arquitetura ereta e alta produtividade é uma demanda cres-cente para os melhoristas. O escurecimento lento de grãos permitirá aumentar o tempo de armazenamento, proporcionando aos produtores flexibilidade no momento de venda e, consequentemente, maior lucratividade. Estudos têm demostrado a existência de variabili-dade genética para este caráter, possibilitando a seleção de linhagens com escurecimento lento de grãos. Os objetivos do presente trabalho foram i) estimar os parâmetros genéticos e fenotípicos de linhagens obtidas de quatro populações segregantes de feijoeiro-comum; ii) selecionar linhagens que associem escurecimento lento dos grãos, arquitetura de plantas ereta e alta produtividade; iii) verificar a existência de associação entre o escurecimento lento e o tempo de cocção dos grãos, após o armazenamento, iv) avaliar dois métodos de indução do escurecimento dos grãos; e v) validar os marcadores SSR Pvsd-1158 e PVM02TC116, associados ao escurecimento dos grãos. As linhagens avaliadas foram ori-undas de quatro populações segregantes, derivadas do cruzamento entre a cultivar de escu-recimento lento dos grãos BRSMG Madrepérola e os genitores BRS Estilo, BRS Cometa, BRS Notável e CNFC 10429. Foram instalados três ensaios com 220 linhagens, sendo 55 de cada população, e os cinco genitores, em delineamento experimental látice 15x15, com parcelas de duas linhas de três metros em três locais. Os experimentos foram realizados na safra de inverno/2012, sendo um em Santo Antônio de Goiás e outros dois em Brasília. Os caracteres avaliados foram produtividade de grãos, arquitetura de plantas, escurecimento de grãos, massa de cem grãos e tempo de cocção. Foram estimados componentes de vari-ância, parâmetros genéticos e fenotípicos e coeficientes de correlação fenotípica, genética e ambiental entre o escurecimento de grãos e tempo de cocção aos 90 e aos 180 dias após a colheita. Foi realizada a comparação entre os métodos de indução de escurecimento acele-rado e prolongado. A partir dos marcadores Pvsd-1158 e PVM02TC116, identificados co-mo previamente ligados ao gene que controla o escurecimento dos grãos, estimou-se a fre-quência de recombinação e a eficiência de seleção dos marcadores para cada população em cada ambiente. Para escurecimento lento dos grãos as estimativas de herdabilidade, variân-cia genética e ganho esperado com a seleção foram elevadas, indicando boa possibilidade de sucesso com a seleção. Para produtividade, arquitetura de plantas e tamanho comercial dos grãos, as estimativas de herdabilidade e variância genética foram elevadas, no entanto, não evidenciou altos ganhos com a seleção simultânea. As quatro populações possibilitaram a obtenção de linhagens com escurecimento lento dos grãos, sendo BRSMG Madrepé-rola x BRS Estilo e BRSMG Madrepérola x BRS Cometa as que forneceram maior número de linhagens que associaram o escurecimento lento com arquitetura ereta, alta produtivida-de e tamanho comercial de grãos. Não foi identificada correlação genética importante entre o escurecimento e tempo de cocção dos grãos, portanto, grãos claros não são indicativo de baixo tempo de cocção. Os métodos de indução ao escurecimento, prolongado e acelerado, permitem discriminar as linhagens que possuem escurecimento lento e normal e fornecem informações semelhantes. As estimativas de frequência de recombinação para o marcador Pvsd- 1158 foram sempre baixas, indicando que o marcador é intimamente ligado ao gene que controla escurecimento lento, sendo estável nos diferentes ambientes e populações. Já o marcador PVM02TC116 não se mostrou polimórfico em três das quatro populações, para a população polimórfica, apresentou elevada frequência de recombinação, sendo, pois, inadequado para utilização da seleção assistida para escurecimento dos grãos.

Submitted by Marlene Santos (marlene.bc.ufg@gmail.com) on 2016-09-09T20:17:53Z No. of bitstreams: 2 Dissertação - Daniany Rodrigues Adorno Silva - 2016.pdf: 3317454 bytes, checksum: 2a1e85ca0c09e0b89edfaf2b184ee8e7 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2016-09-12T14:20:21Z (GMT) No. of bitstreams: 2 Dissertação - Daniany Rodrigues Adorno Silva - 2016.pdf: 3317454 bytes, checksum: 2a1e85ca0c09e0b89edfaf2b184ee8e7 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2016-09-12T14:20:21Z (GMT). No. of bitstreams: 2 Dissertação - Daniany Rodrigues Adorno Silva - 2016.pdf: 3317454 bytes, checksum: 2a1e85ca0c09e0b89edfaf2b184ee8e7 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-08-12 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The rice (Oryza sativa) is a staple food for the majority of the world's population. One of the main challenges for the breeding programs of this crop is the increase of the yield potential of commercial cultivars. For the development of superior lines and cultivars is necessary to identify and incorporate superior alleles in genetic breeding programs. One of the alterna-tives for the identification of useful genetic variability is the crossing involving genetically unrelated parents, as well as genotyping and phenotyping the segregating populations de-rived from these crossings, and posterior analysis of QTL (Quantitative Trait Locus). This study aimed to identify genes associated with yield of grains in rice through Genotyping by Sequencing (GBS), field experiments and a posterior analysis of QTL involving 232 RIL’s (Recombinant Inbred Lines) derived from the inter-subspecific crossing Epagri 108 (indica) x IRAT 122 (japonica) in two locations (Goianira - State of Goias and Boa Vista - State of Roraima). For the QTL analysis it was mapped 2,382 SNP markers, which identified two QTLs for yield, both located on chromosome 6, exclusively for the experiment of Goianira. The average effects of allele substitutions were 1,365.20 kg.ha-1 and 1,075.49 kg.ha-1, and the proportions of the phenotypic variance explained by the QTLs were 18% and 29%, clas-sified as QTL of large effect. All favorable alleles for yield were derived from genitor IRAT 122. One of the QTL identified to the productivity showed interaction QTL x E, which was expected due to the high significance of interactions G x E detected in the joint analysis. For the experiment of Goianira was also analyzed the trait hundred grain weight, and it were found three QTLs on chromosomes 5, 6 and 12. The average effects of the allelic substitution for the hundred grain weight ranged from 0.12 to 0.14 grams. The proportions of the pheno-typic variance explained by the QTLs ranged from 6 to 8%. Approximately 84% of the QTLs for the hundred grain weight were obtained from the parent IRAT 122. In chromosomal regions identified QTLs for grain yield are contained two genes: the LOC_Os06g16870, a transposon En/Spm, and the LOC_Os06g33320 whose function remains unknown, but whose expression was almost exclusively found in the inflorescences of rice. For the hundred grain weight, the chromosome region of the QTL located on chromosome 5 is located in a linkage block with 82 genes that co-segregate, and whose putative functions include, among others, the adjustment of tillering, pollen formation, grain filling and resistance to abiotic stress. For the QTL located on chromosome 6 it was identified the gene LOC_Os06g16160, which the function still unassigned, but whose expression is located almost exclusively in the root. On chromosome 12, the QTL containing the gene LOC_Os12g41956 expresses a protein of the galactosyl-transferase family, which participates in the synthesis of the RFO’s (Raffinose Family of Oligosaccharides), regulating the levels of reserve oligosaccharides in seeds. / O arroz (Oryza sativa) é um alimento básico para a maioria da população mundial. Um dos principais desafios para os programas de melhoramento dessa cultura é o aumento do poten-cial produtivo de cultivares comerciais. Para o desenvolvimento de linhagens e cultivares superiores é necessário que sejam incorporados alelos superiores em genitores dos progra-mas de melhoramento. Uma das alternativas para a identificação da variabilidade genética útil é a realização de cruzamentos envolvendo genitores pouco aparentados e a genotipagem e fenotipagem de populações segregantes derivadas desses cruzamentos, com uma posterior análise de QTL (locos de caracteres quantitativos). Esse trabalho teve por objetivo identificar genes associados à produtividade de grãos em arroz por meio da genotipagem por sequenci-amento (GBS), experimentos de campo e uma posterior análise de QTL envolvendo 232 RILs (linhas puras recombinantes) derivadas do cruzamento inter-subespecífico Epagri 108 (indica) x IRAT 122 (japonica) em dois locais (Goianira-GO e Boa Vista-RR). Para a análise de QTL foram mapeados 2.382 marcadores SNPs, os quais identificaram dois QTLs para produtividade, ambos localizados no cromossomo 6, exclusivamente para o experimento de Goianira. Os efeitos médios de substituição alélica foram de 1.365,20 kg.ha-1 e 1.075,49 kg.ha-1, e as proporções das variâncias fenotípicas explicadas pelos QTLs foram de 18% e 29%, classificadas como QTLs de grandes efeitos. Todos os alelos favoráveis para produti-vidade foram provenientes do genitor IRAT 122. Um dos QTLs identificados para a produ-tividade apresentou interação QTL x E, o que já era esperado devido à alta significância das interações G x E detectadas na análise de variância conjunta. Para o experimento de Goianira também foi analisado o peso de 100 grãos, e foram encontrados três QTLs, localizados nos cromossomos 5, 6 e 12. Os efeitos médios de substituição alélica para o peso de 100 grãos variaram de 0,12 a 0,14 gramas. As proporções da variância fenotípica explicadas pelos QTLs variaram de 6 a 8%. Cerca de 84% dos QTLs identificados para o peso de 100 grãos foram provenientes do genitor IRAT 122. Nas regiões cromossômicas dos QTLs identifica-dos para produtividade de grãos estão contidos dois genes: o LOC_Os06g16870, um trans-poson En/Spm, e o LOC_Os06g33320, de função ainda desconhecida, mas cuja expressão foi quase que exclusivamente identificada nas inflorescências de arroz. Para o peso de 100 grãos, a região cromossômica do QTL localizado no cromossomo 5 está contido em um bloco de ligação contendo 82 genes que co-segregam, e cujas funções putativas incluem, dentre outras, a regulação do perfilhamento, formação de pólen, enchimento de grãos e re-sistência a estresse abiótico. Para o QTL identificado no cromossomo 6, nesta região cro-mossômica está presente o gene LOC_Os06g16160, ainda sem atribuição de função, mas cuja expressão está localizada quase que exclusivamente na raiz. Já no cromossomo 12, a região cromossômica do QTL contém o gene LOC_Os12g41956, que expressa uma proteína 15 da família galactosil-transferase, que participa da síntese dos RFOs (oligossacarídeos da fa-mília das rafinoses), regulando os níveis de oligossacarídeos de reserva nas sementes

Estudos genético quantitativos e moleculares são fundamentais para o melhoramento animal e sua realização com a raça Nelore é de grande importância devido a ampla participação dessa no rebanho de corte nacional. A estimação constante dos parâmetros genéticos das características de produção é necessário para a adequada condução do processo de seleção dos animais. A melhoria de características relacionadas à carcaça bovina é essencial para a eficiência e sustentabilidade da atividade e a implementação de métodos de seleção animal baseados em informações moleculares pode revolucionar a produção zootécnica e deve ser profundamente estudado. Sendo assim, os objetivos do presente estudo foram estimar parâmetros genéticos e componentes de variância através de diferentes modelos matemáticos para um total de 14 características fenotípicas (o peso ao nascimento, peso a desmama, peso ao sobreano, ganho de peso entre a desmama e o sobreano ajustado para um intervalo de 345 dias, perímetro escrotal ao sobreano, altura de garupa ao sobreano, escores visuais avaliados ao sobreano de conformação, precocidade, musculosidade, comprimento de umbigo e ossatura, e ainda características de carcaça mensuradas por ultrassonografia realizada após 30 a 45 dias de confinamento como a área de olho de lombo, espessura de gordura subcutânea, espessura de gordura na picanha). Foram estimadas correlações entre todas estas características com as de carcaça mensuradas por ultrassonografia. Sob o enfoque molecular, desenvolveu-se um programa para imputação de genótipos faltantes e estudaram-se diferentes métodos de associação de marcadores moleculares do tipo mutação de base nitrogenada única (SNP) a características de produção incluídas no índice de seleção de um programa de melhoramento da raça Nelore, utilizando inferência bayesiana. Todas as características estudadas podem ser selecionadas esperando-se progresso genético na população. Os efeitos maternos foram importantes em algumas características onde normalmente estes efeitos não têm sido considerados atualmente. A quantidade de escores atribuídos a uma característica categórica assim como o número de observações fenotípicas resultam em diferenças nas estimativas quando avaliadas por modelos lineares ou de limiar. Não deverão ser obtidos resultados satisfatórios na melhoria das características de carcaça se a seleção for baseada nas tradicionais avaliações visuais utilizadas no momento. Os métodos utilizados na análise de associação dos marcadores podem originar diferentes resultados. Os marcadores que apresentaram efeitos altamente relevantes (P<0,01) geralmente apresentaram resultados semelhantes, independentemente do método utilizado. Certos marcadores podem ter efeitos positivos para algumas características componentes do índice de seleção e negativos para as demais. A análise em conjunto com todos os SNP\'s e todos os dados fenotípicos disponíveis é viável e parece ser a mais adequada. O método desenvolvido de imputação de genótipos faltantes a partir do parentesco de animais genotipados foi eficiente. / Quantitative and molecular genetic studies are very important for animal breeding and studies with Nellore cattle have great importance due to the large participation of that breed in the Brazilian beef cattle industry (around 80% of the herd). The constant estimation of genetic parameters for traits linked to production is necessary for properly perform selection of animals. The improvement of carcass traits is essential for efficiency and profitability of the activity. The implementation of methods for animal selection based on molecular information could revolutionize animal production and should be deeply studied. Thus, the objectives of this study were to estimate genetic parameters and variance components using different mathematical models for a total of 14 traits, such as birth weight, weaning weight, yearling weight, post-weaning weight gain between weaning and yearling adjusted for 345 days, yearling scrotal circumference, yearling hip height, yearling visual scores like conformation, finishing, muscularity, bone structure and navel length. Ultrasound measurements for carcass traits performed at feedlot (30 to 45 days, at approximate age of 20 months) such as rib-eye area, fat thickness, rump fat thickness were, also, evaluated. Estimate correlations between all these traits with the carcass traits measured by ultrasound were estimated. As concerned to molecular study, an algorithm for imputation of missing genotypes was developed and different methods to analyze molecular marker (single nucleotide polymorphism - SNP) association with traits components of the selection index of a breeding program that is applied to the population studied, using bayesian inference, were used. Genetic progress will be expected for selection of all the traits studied. Maternal effects were important in some traits in which those effects are not usually considered. The amount of scores assigned to a categorical trait and the number of observations could result in different estimates when evaluated by linear or threshold models. The selection for visual scores traditionally used in that population will not improve carcass traits. The methods used to analyze the association of markers may lead to different results. The SNP\'s with association effects of high relevance (P<0.01) generally express their effects regardless of the method used to analyze. Some markers may have positive effects for some traits of selection index, but negative for others. The joint analysis with all SNPs and with all available phenotypes is feasible and appears to be more appropriate. The algorithm developed for imputation of missing genotypes from pedigree information of genotyped animals was efficient.