Spelling suggestions: "subject:"prebreeding"" "subject:"rebreeding""
1 |
Rôle des effets épistatiques dans l’évolution d’une population à régime de reproduction mixte, et dans la régulation de l’expression des gènes homéologues chez une espèce autogame allotétraploïde, le blé dur (Triticum turgidum). / Role of epistatic effects in the evolution of a population with mixed mating system, and in the regulation of the expression of homoeologous genes in a selfing allotetraploid species, durum wheat (Triticum turgidum).Vagne, Constance 19 December 2014 (has links)
L'épistasie a longtemps été négligée, mais aujourd'hui elle connait un regain d'intérêt avec le développement du séquençage haut-débit et des études d'association pangénomique (GWAS). Elle est quasi-omniprésente, ayant été détectée sur de nombreux traits et chez de nombreuses espèces. Elle joue un rôle important d'un point de vue évolutif, puisqu'elle est à l'origine d'incompatibilités de Dobzhansky-Müller, expliquant l'isolement reproductif entre lignées apparentées. Par ailleurs, chez les polyploïdes à héritabilité disomique (essentiellement des allopolyploïdes), elle peut permettre de fixer l'hétérosis. L'objectif de cette thèse a été d'étudier l'épistasie dans ce contexte évolutif. Le matériel d'étude a été une population à base génétique large d'une espèce autogame allopolyploïde, le blé dur (Triticum turgidum), possédant deux génomes : le génome A et le génome B. Cette population a été constituée à partir de différents taxons : blé dur (T. t. durum), amidonnier domestique (T. t. dicoccum) et amidonnier sauvage (T. t. dicoccoides). Il est donc possible qu'elle présente des combinaisons de gènes coadaptées, et donc de l'épistasie générant des incompatibilités de Dobzhansky-Müller.Une première partie présente différents modèles permettant d'estimer l'épistasie. Ces modèles ont des inconvénients et des avantages, qui dépendent de l'objectif que l'on s'est fixé. Dans une deuxième partie, nous avons utilisé l'un de ces modèles sur des données de RNA-seq (données d'expression et de génotypage) de la population de blé dur, afin de détecter des effets régulateurs de l'expression, et notamment de l'épistasie entre gènes homéologues. Cette analyse est une première pour le blé dur et probablement pour les espèces polyploïdes. Nous n'avons presque pas détecté d'épistasie de premier ordre, mais des interactions avec le fond génétique ont été observées. Nous avons trouvé plus d'eQTL sur le génome B que sur le génome A, ce qui est peut-être dû au fait que les ancêtres diploïdes du blé dur n'avaient pas le même régime de reproduction. Par ailleurs, nous avons montré que les niveaux d'expression des gènes homéologues étaient très fréquemment (80%) corrélés de manière positive, ce qui indique que les gènes homéologues appartiennent fréquemment aux mêmes complexes de gènes corégulés. Enfin, les régulations trans sont plus fréquentes au sein des paires de gènes d'homéologues, ce qui corrobore également l'idée que les gènes homéologues appartiennent aux mêmes réseaux de gènes. Dans une troisième partie, le rôle évolutif de l'épistasie a été examiné. D'abord, nous avons montré comment l'épistasie influençait la covariance parents-enfants, et donc l'évolution à courts termes d'une population. Ensuite, nous avons étudié l'impact d'un type particulier d'épistasie (celui à l'origine des d'incompatibilités de Dobzhansky-Müller, présentant des combinaisons de gènes coadaptés) sur l'évolution d'une population soumise à de la sélection par troncation (comme dans les populations de pre-breeding), à l'aide d'un modèle haploïde bilocus, en fonction du taux de recombinaison et de l'intensité de la sélection. Nous avons montré que si le génotype optimal n'est pas présent dans la population initiale, un fort taux de recombinaison risque de mener à la fixation du génotype sous-optimal. Néanmoins, un peu de recombinaison est nécessaire pour créer ce génotype optimal et le fixer.En perspectives, nous proposons d'adopter une méthode basée sur les réseaux de gènes pour approfondir les mécanismes de la régulation de l'expression chez le blé dur. Nous proposons également de complexifier le modèle permettant d'étudier l'effet de la recombinaison sur l'évolution d'un trait épistatique, sélectionné par troncation, et de compléter ces travaux de modélisation par des études expérimentales. / Epistasis has long been neglected, but it is currently subject to a renewed interest with the development of high-throughput sequencing technologies and of genome-wide association studies (GWAS). It is virtually ubiquitous, having been detected on many traits and in many species. It plays an important evolutionary role, since it is one of the sources of Dobzhansky-Muller incompatibilities, explaining reproductive isolation between related lineages. Moreover, it can enable to fix heterosis in disomic polyploids (mostly allopolyploids). The objective of this thesis was to study epistasis in this evolutionary context. The study material was a broad genetic basis population of a self-pollinating allopolyploid species, durum wheat (Triticum turgidum), having two genomes: A and B genomes. This population was composed from different taxa: durum wheat (T. t. durum), domestic emmer (T. t. dicoccum) and wild emmer (T. t. dicoccoides). Therefore, there are probably combinations of coadapted genes in this population, and thus epistasis generating Dobzhansky-Muller incompatibilities.The first part presents different models to estimate epistasis. These models have advantages and drawbacks, depending on the overall objective. In a second part, we used one of these models on RNA-seq data (expression and genotyping data) of the population of durum wheat to detect regulatory effects of expression, including epistasis between homoelogous genes. This analysis is unique in durum wheat, and probably in polyploid species. We did not detect first-order epistasis, but interactions with genetic background were observed. We found more eQTL on the B genome than on the A genome, which may be due to the fact that the diploid progenitors of durum wheat did not have the same mating system. Furthermore, we showed that the expression levels of homoelogous genes were frequently (80%) positively correlated, indicating that homoelogous genes often belong to the same complex of coregulated genes. Finally, trans regulations are more common among pairs of homoelogous genes, which also supports the idea that homoelogous genes belong to the same gene networks. In the third part, the evolving role of epistasis was examined. First, we showed how epistasis influences the parent-offspring covariance, and thus the short-term evolution of a population. Then we studied the impact of a particular type of epistasis (the one which can generate Dobzhansky-Muller incompatibilities, with combinations of co-adapted genes) on the evolution of a population subjected to truncation selection (as in pre-breeding populations), using a haploid bilocus model, based on the recombination rate and selection intensity. We have shown that if the optimal genotype is not present in the initial population, a high rate of recombination may lead to the fixation of the sub-optimal genotype. However, some recombination is needed to create this optimal genotype and fix it.In perspective, we propose to adopt a network-based method to further the regulation mechanisms of expression in durum wheat. We also propose to make the model more complex, in order to study the effect of recombination on the evolution of an epistatic trait selected by truncation, and complete these modelling works by experimental studies.
|
2 |
Pre-Breeding to Improve Yield and Disease Resistance of Hard Red Winter WheatBarry, Dylan Mitchell January 2020 (has links)
Challenges to growing winter wheat in North Dakota include winter temperature and disease pressure. Fusarium head blight (FHB) is a devastating disease that necessitates breeding for resistance. In the NDSU breeding program FHB resistance genes are often associated with a decrease in performance. This study used single seed descent to advance lines while maintaining a near random population. Early generation (F4) selection focused heavily on yield and the presence of FHB resistance quantitative trait loci to develop winter wheat lines with FHB resistance and high yield.
Stripe rust is a fungal disease that is becoming increasingly problematic in North Dakota. To assess the available stripe rust resistance in the NDSU winter wheat germplasm, two sets of diverse breeding lines were used for stripe rust resistance phenotyping and genotyping by sequencing. The phenotype and genotype data were then used to locate resistance genes through genome wide association study.
|
3 |
Avaliação de genótipos de melancia quanto à resistência à mancha aquosaCARVALHO, Francisco Conrado Queiroz Carvalho 29 February 2012 (has links)
Submitted by (lucia.rodrigues@ufrpe.br) on 2017-03-10T15:33:36Z
No. of bitstreams: 1
Francisco Conrado Queiroz Carvalho.pdf: 693930 bytes, checksum: 0e5f734618ab807f4c62e74984f62954 (MD5) / Made available in DSpace on 2017-03-10T15:33:36Z (GMT). No. of bitstreams: 1
Francisco Conrado Queiroz Carvalho.pdf: 693930 bytes, checksum: 0e5f734618ab807f4c62e74984f62954 (MD5)
Previous issue date: 2012-02-29 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Bacterial fruit blotch caused by Acidovorax citrulli occurs in different parts of watermelon plant, at different stages of development but symptoms are more conspicuous and easy to diagnose in fruit. BFB has caused significant economic losses to melon production in Brazil and is a major threat to the watermelon fields. This justifies the research for resistance sources to be used in breeding programs aiming to obtain varieties resistant to BFB, since they do not yet exist. To select genotypes with potential use in the management of fruit blotch, the resistance level of watermelon genotypes belonging to the Cucurbits Germplasm Active Bank for the Brazilian Northeast (Banco Ativo de Germoplasma de Cucurbitáceas para o Nordeste Brasileiro - BAG) of Embrapa Semiárido was evaluated at different plant developmental stages: seeds (74 genotypes), seedlings and plants before flowering (29 genotypes) as well as plants during flowering and fruiting (7 genotypes). The genotypes were evaluated for the incidence or severity of the disease, which was estimated with the aid of descriptive scales. Additionally, A. citrulli transmission was determined in seeds derived from symptomatic and asymptomatic fruits. No watermelon genotype was immune to fruit blotch, and the majority showed variations in resistance responses. However, the genotypes BGCIA 979, BGCIA 34 and Sugar Baby showed high levels of resistance at most stages of plant development, thereby suggesting that these genotypes possess fruit blotch resistance genes that could be used in breeding programs. Seeds from symptomatic and asymptomatic fruits of the seven tested genotypes showed transmission rates of A. citrulli up to 35.3% and 8.7%, respectively. These results confirm that asymptomatic fruits can harbor contaminated seeds that are responsible for the transmission of the bacteria. / A mancha aquosa, causada pela bactéria Acidovorax citrulli, ocorre em distintos órgãos de melancia, em diferentes estádios de desenvolvimento, sendo os sintomas mais comuns e de fácil diagnose nos frutos. Essa doença é responsável por elevadas perdas econômicas na cultura do meloeiro no Brasil e uma grande ameaça para a melancia. Isto justifica a busca de fontes de resistência a serem utilizadas em programas de melhoramento visando à obtenção de variedades dessa olerícola com resistência a doença. Com o objetivo de selecionar genótipos com potencial de utilização no manejo da mancha aquosa, avaliou-se o nível de resistência de 74 genótipos de melancia pertencentes ao Banco Ativo de Germoplasma de Cucurbitáceas para o Nordeste Brasileiro (BAG) da Embrapa Semiárido, em diferentes estádios de desenvolvimento da planta: sementes (74 genótipos), plântulas e plantas antes da floração (29 genótipos), plantas durante a floração e frutificação (7 genótipos). Os genótipos foram avaliados quanto a incidência ou severidade da doença, esta estimada com auxílio de escalas descritivas. Adicionalmente, foi determinada a transmissão de A. citrulli em sementes oriundas de frutos sintomáticos e assintomáticos. Nenhum genótipo de melancia foi imune à mancha aquosa, e a maioria apresentou variação nas reações de resistência. Porém, os genótipos BGCIA 979, BGCIA 34 e ‘Sugar Baby’ mostraram altos níveis de resistência na maioria dos ensaios realizados, indicando possuírem genes para resistência à mancha aquosa que poderão ser utilizados em programas de melhoramento. Sementes de frutos sintomáticos e assintomáticos dos sete genótipos apresentaram transmissão de A. citrulli de até 35,3% e 8,7% respectivamente, confirmando que frutos assintomáticos podem abrigar sementes contaminadas responsáveis pela transmissão da bactéria.
|
4 |
Caracterização genética, morfológica e agronômica de germoplasma de sacha inchi (plukenetia volubilis L.) no estado do Amazonas / Genetic, morphological and agronomic characterization of sacha inchi germoplasm (Plukenetia volubilis L.) in the state of amazonasRodrigues, Haroldo Silva 18 July 2013 (has links)
Made available in DSpace on 2015-03-26T13:42:30Z (GMT). No. of bitstreams: 1
texto completo.pdf: 759469 bytes, checksum: 33ae9554924588966908ce701f540e81 (MD5)
Previous issue date: 2013-07-18 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Although widely known and rich in biodiversity, the Amazon still has a range of species that are underexplored and neglected by science, these species may have great potential for man. Only a fraction of the Amazon biodiversity is known. It is estimated that the plant wealth comprises about 30,000 species, about 10% of plants from all over the planet. The sacha inchi is a native plant from the Amazon, with great potential for the pharmaceutical and cosmetic industry. This plant has high amounts of monounsaturated and polyunsaturated fatty acids in the oil that is extracted from its seeds. Studies on the oil characteristics are found in scientific journals. On the other hand, there is a lack of studies that measure the genetic diversity among genotypes of sacha inchi. Embrapa Western Amazon, located in Manaus, has a sacha inchi Germplasm Bank which is composed of 37 accessions. This work was aimed to measure the genetic diversity within and between accessions in this collection through molecular markers and phenotypic traits related to fruits and seeds. AFLP markers were used and the results obtained the genetic dissimilarity was calculating by the arithmetic complement of Jaccard coefficient and subsequent construction cluster by using the UPGMA method. The phenotypic data collected was subjected to variance analysis, classified with average grouping by the Skott-Knott method, Mahalanobis distance method and clustered by the UPGMA method. Also performed canonical correlation analysis and the study of diversity within and between accessions using the method of AMOVA. The results showed the following; the existence of genetic variability among genotypes, the molecular analysis revealed geographic structure among accessions, the phenotypic data affirmed that there is great variation between means of most of the variables considered in this work, it was not possible to detect statistically significant correlations between variables related to fruit and variables related to seed tough.For breeding purposes, the exploration of diversity within the accessions and crosses between divergent accessions should be adopted. / Apesar de amplamente conhecida e rica em biodiversidade, a região amazônica ainda possui uma gama de espécies subexploradas e negligenciadas pela comunidade científica, espécies essas que apresentam grande potencial de utilização para o homem. Apenas uma pequena fração dessa biodiversidade é conhecida, estima-se que a riqueza da flora amazônica compreende aproximadamente 30.000 espécies, cerca de 10% das plantas de todo o planeta. A sacha inchi é uma espécie nativa da amazônica com grande potencial de uso para a indústria farmacêutica e estética, pois possui alto teor de ácidos graxos mono e poliinsaturados no óleo extraído de sua semente. Apesar de estudos sobre características desse óleo serem encontrados na literatura, existe uma grande carência de trabalhos que mensurem a diversidade genética entre genótipos de sacha inchi. A Embrapa Amazônia Ocidental, situada no município de Manaus, possui um Banco de Germoplasma de sacha inchi composto por 37 acessos. O presente trabalho teve como objetivo estudar a diversidade genética entre e dentro dos acessos componentes dessa coleção por meio de marcadores moleculares e características fenotípicas relacionadas à produção de frutos e sementes. Foram utilizados marcadores AFLP e os resultados obtidos, submetidos à análise de dissimilaridade por meio do cálculo do complemento aritmético do coeficiente de Jaccard e subsequente construção dendograma pelo método UPGMA. Os dados fenotípicos coletados foram submetidos à analise de variância e subsequente analise de agrupamento de médias pelo método Skott-Knott, distância generalizada de Mahalanobis e dendograma construído pelo método UPGMA. Foi realizada ainda a análise de correlações canônicas e estudo da diversidade entre e dentro dos acessos utilizando o método da AMOVA. Os resultados obtidos mostram a existência de variabilidade genética entre os acessos estudados, o estudo à nível molecular mostrou estruturação geográfica entre os acessos estudados, os dados fenotípicos mostram que existe grande amplitude entre as médias de maioria das variáveis consideradas neste trabalho, por outro lado não foi possível detectar correlações estatisticamente significativas entre variáveis relacionadas ao fruto e variáveis relacionadas à semente. Para fins de melhoramento genético deve-se adotar a exploração da diversidade dentro dos acessos e optar por cruzamentos entre acessos divergentes.
|
5 |
Caracterização morfológica, molecular e reprodutiva de híbridos interespecíficos de Arachis na busca de resistência a pragas do amendoim / Morphological, molecular and reproductive characterization of interspecific hybrids of Arachis resistant to pestsPaula, Ailton Ferreira de 23 March 2015 (has links)
Submitted by Bruna Rodrigues (bruna92rodrigues@yahoo.com.br) on 2016-09-15T20:16:51Z
No. of bitstreams: 1
DissAFP.pdf: 3433362 bytes, checksum: 873b79f0c665e16e5c7c85ca69f042dd (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-09-16T19:58:31Z (GMT) No. of bitstreams: 1
DissAFP.pdf: 3433362 bytes, checksum: 873b79f0c665e16e5c7c85ca69f042dd (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-09-16T19:58:37Z (GMT) No. of bitstreams: 1
DissAFP.pdf: 3433362 bytes, checksum: 873b79f0c665e16e5c7c85ca69f042dd (MD5) / Made available in DSpace on 2016-09-16T19:58:43Z (GMT). No. of bitstreams: 1
DissAFP.pdf: 3433362 bytes, checksum: 873b79f0c665e16e5c7c85ca69f042dd (MD5)
Previous issue date: 2015-03-23 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / The peanut (Arachis hypogaea) is, worldwide, an important source of protein and oil. Pests and foliar diseases are among the factors that limit the economically sustainable production of peanuts in Brazil. Among the pests, thrips and the rednecked peanutworm are considered important pests in São Paulo State. To decrease the cost of production on the management of these pests, genetic improvement to obtain resistant varieties from wild plants is a viable alternative. The main obstacle in the genetic improvement is that the vast majority of wild species of Arachis is diploid, while the cultivated species is allotetraploid. For the barrier of ploidy between the wild and the cultivated peanut to be broken, it is
necessary to obtain interspecific hybrids genome AB. Such hybrids should be treated with colchicine to induce polyploidy and get fertile hybrids with two distinct complete genomes (amphidiploid), which can be crossed with A. hypogaea to get the same or similar genomic constitution of the cultivated species. The aim of the research were to identify hybrids derived from crosses made between wild species with A, B or K genome that are resistant to thrips and the rednecked peanutworm and hybrids from one amphidiploid and A. hypogaea, characterize the hybrids and their parents 1) by microsatellite molecular
markers, 2) by pollen viability and 3) by their morphology. The molecular markers were genotyped in polyacrylamide gel with standard 10 base pairs. The viability of pollen grains was used to analyze the data of analysis of variance and mean Tukey test, and morphological data were analyzed by Principal Component Analysis. Six polymorphic microsatellite loci were analyzed in 25 F1 plants, 18 of them result of selfing and six of hybridization with a total of three different hybrid combinations plus four hybrid plants from across between the amphidiploid An 13 and A. hypogaea. The pollen viability data
corroborated the molecular analysis in the identification of hybrids, noting that An 13 had high viability of pollen grains and interspecific hybrids had low values when compared to their parents and selfed individuals of progeny. From the 63 morphological descriptors measured the ones from the main axis expressed the most morphological variation observed. Pollen viability of F1 hybrid plants obtained by cross among A. hypogaea and the amphidiploid An 13 was above 76%, showing the possibility of new interesting genes introgression in A. hypogaea / O amendoim (Arachis hypogaea) representa, ao nível mundial, uma importante fonte de proteína e óleo. As pragas e doenças da parte aérea estão entre os fatores que mais limitam a produção economicamente sustentável do amendoim no Brasil. Dentre as pragas, o tripes e a lagarta-do-pescoço-vermelho são consideradas as pragas-chave no Estado de São Paulo. Para diminuir o custo da produção diante ao manejo destas pragas, o melhoramento genético para a obtenção de plantas resistentes a partir de plantas silvestres é uma alternativa viável. O principal entrave no melhoramento genético é que a grande maioria das espécies silvestres de Arachis é diplóide, enquanto que a espécie cultivada é alotetraploide. Para que a barreira da ploidia entre o amendoim silvestre e o cultivado possa ser quebrada, é necessária a obtenção de híbridos interespecíficos de genoma AB. Tais híbridos devem ser tratados com colchicina, no intuito de induzir a poliploidização e
obter híbridos férteis com dois genomas completos distintos (anfidiplóide), que poderão ser cruzados com A. hypogaea por terem a mesma ou similar constituição genômica da espécie cultivada. Os objetivos do trabalho foram identificar híbridos oriundos de cruzamentos realizados entre espécies silvestres resistentes a tripes e a lagarta-do-pescoço-vermelho de
genoma A, B ou K, identificar híbridos entre um anfidiplóide e A. hypogaea e caracterizar os híbridos e seus genitores 1) via marcadores moleculares tipo microssatélites, 2) quanto à viabilidade de grãos de pólen e 3) quanto a sua morfologia. Os marcadores moleculares foram genotipados em gel de poliacrilamida com padrão de 10 pares de base, para analisar
os dados da viabilidade de grãos de pólen foi utilizada análise de variância e teste de médias Tukey e os dados da caracterização morfológica foram analisados via análise de componentes principais. Foram analisados seis locos microssatélites polimórficos, em vinte cinco plantas F1, sendo quatorze delas resultado de autofecundação e onze de
hibridação, totalizando três combinações híbridas distintas diplóides mais quatro plantas híbridas entre A. hypogaea e o anfidiplóide An 13. Os dados de viabilidade de pólen corroboraram a análise molecular na identificação dos híbridos, observando-se que o An 13 possuía alta viabilidade de grãos de pólen e os híbridos interespecíficos possuíam valores muito abaixo dos genitores e dos indivíduos autofecundados da progênie. Quanto às analises morfológicas, dos 63 descritores mensurados, os descritores do eixo central foram os que mais expressaram a variação morfológica observada. A viabilidade de grãos de pólen das plantas híbridas F1 entre A. hypogaea e o anfidiplóide An 13 foi acima de 76%, mostrando a possibilidade de introgressão de novos genes de interesse em A. hypogaea.
|
6 |
Pré-melhoramento visando resistência à requeima em tomateiro / Pre-breeding for resistance to late blight in tomatoLaurindo, Bruno Soares 17 July 2013 (has links)
Made available in DSpace on 2015-03-26T13:39:59Z (GMT). No. of bitstreams: 1
texto completo.pdf: 425667 bytes, checksum: 1f8c842faf40449adebf9de5ae50ad48 (MD5)
Previous issue date: 2013-07-17 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / The tomato production is considered a high risk economic activity, and of great agronomic complexity mainly because of the high number of pathogens that causes diseases in the culture. Among the pathogens of greatest importance, there is the oomycete Phytophthora infestans (Mont.) de Bary, causing late blight, which is considered the most destructive disease of tomato. There are no commercial tomato cultivars resistant and the control of this disease is highly dependent on the use of fungicides. Considering that the tomato is one of the most studied crop in genetic terms, the lack of resistant cultivars in the market reflects the difficulty in working this trait in breeding programs. The objectives with this present study was to select sources of resistance to late blight among accessions of Solanum lycopersicum, and estimate the overall and specific ability of combining six tomato accessions of Solanum lycopersicum selected for resistance to late blight, aiming at the selection of potential genitors for pre-breeding for resistance to this disease. Two experiments were carried out. In the first, twelve accessions of S. lycopersicum, from the Vegetable Germplasm Bank of the Federal University of Viçosa - BGH - UFV (BGH-973, BGH-1025, BGH- 2017, BGH-2093, BGH-2095, BGH-2102, BGH-2117, BGH-2127, BGH-2130, BGH- 2332, BGH-2333 and BGH-2343) were evaluated in a randomized block design with three replications. For the evaluation of the resistance, the plants were inoculated with a mixture of sporangia of P. infestans, in the concentration of 5x103 sporangia mL-1 , collected in different regions of the Zona da Mata Mineira. It was evaluated the percentage of plant tissue affected by the disease, or the percentage of severity, evaluated in the form of area under the disease progress curve (AUDPC). The accessions BGH-2102, BGH-2117, BGH-2127, BGH-2130, BGH-2332 and BGH-2343 obtained average values of AUDPC lower than the resistant controls, and were selected as a source of resistance to late blight. The selected accessions as resistant to late blight were used in a second experiment, where a balanced diallel of half table were realized, and fifteen F1 s hybrids were obtained. The six accessions of S. lycopersicum, BGH- 2102, BGH-2117, BGH-2127, BGH-2130, BGH-2332 and BGH-2343 together with the fifteen F1 s hybrid were evaluated in a randomized block design with three replications. For the evaluation of the resistance, the plants were inoculated with a mixture of sporangia of P. infestans, in the concentration of 5x103 sporangia mL-1 collected in different regions of the Zona da Mata Mineira. The percentage of plant tissue affected by the disease, or the percentage of severity, presented in the form of area under the disease progress curve (AUDPC) were evaluated. The diallelic analysis was carried out according to the model of GRIFFING (1956). Observed existence of additive genetic variability between the genitors and the predominance of additive gene effects involved in determining the AUDPC, besides the existence of bidirectional dominance deviations in the control of the character. The diallel analysis was efficient in selecting genitors aimed at a pre-breeding of resistance to late blight, highlighting the accessions BGH- 2117, BGH-2127 and BGH-2343 with the greatest frequency of favorable alleles and divergent, thus they can be included in crossings aiming the pre-breeding for resistance to late blight. / A tomaticultura é considerada uma atividade de elevado risco econômico e grande complexidade agronômica, principalmente pelo elevado número de patógenos que causam doenças na cultura. Entre os patógenos de maior importância, destaca-se o oomiceto Phytophthora infestans (Mont.) de Bary, causador da requeima ou mela, considerada a doença mais destrutiva do tomateiro. Não existem cultivares comerciais de tomate resistentes, e o controle da doença é altamente dependente do uso de fungicidas de caráter preventivo e/ou curativo. Considerando que o tomateiro é uma das plantas cultivadas mais bem estudadas em termos genéticos, a inexistência de cultivares resistentes no mercado reflete a dificuldade em se trabalhar essa característica nos programas de melhoramento. Os objetivos com o presente estudo foram selecionar fontes de resistência à requeima entre acessos de Solanum lycopersicum, e estimar as capacidades geral e específica de combinação dos acessos de S. lycopersicum selecionados quanto a resistência à requeima, visando selecionar potenciais genitores para o pré-melhoramento da resistência a esta doença. Foram realizados dois experimentos. No primeiro avaliou-se doze acessos de S. lycopersicum, do Banco de Germoplasma de Hortaliças da Universidade Federal de Viçosa BGH UFV (BGH- 973, BGH-1025, BGH-2017, BGH-2093, BGH-2095, BGH-2102, BGH-2117, BGH- 2127, BGH-2130, BGH-2332, BGH-2333 e BGH-2343) no delineamento em blocos casualizados, com três repetições. Para a avaliação da resistência, as plantas foram inoculadas com uma mistura de esporângios de P. infestans, na concentração de 5x103 esporângios mL-1, coletados em diferentes regiões da Zona da Mata Mineira. Avaliou-se a porcentagem do tecido vegetal afetado pela doença, ou seja, a porcentagem de severidade, avaliada sob a forma de área abaixo da curva de progresso da doença (AACPD). Os acessos BGH-2102, BGH-2117, BGH-2127, BGH-2130, BGH-2332 e BGH-2343 obtiveram valores médios de AACPD inferiores aos das testemunhas resistentes, sendo selecionados como fonte de resistência à requeima. Os acessos selecionados como resistentes à requeima foram utilizados em um segundo experimento, onde foi realizado um dialelo balanceado de meia tabela, e obtidos quinze híbridos F1 s. Os seis acessos de S. lycopersicum, BGH-2102, BGH-2117, BGH-2127, BGH-2130, BGH-2332 e BGH-2343 juntamente com os quinze híbridos F1 s foram avaliados em delineamento em blocos casualizados, com três repetições. Para a avaliação da resistência, as plantas foram inoculadas com uma mistura de esporângios de P. infestans, na concentração de 5x103 esporângios mL-1, coletados em diferentes regiões da Zona da Mata Mineira. Avaliou-se a porcentagem do tecido vegetal afetado pela doença, ou seja, a porcentagem de severidade, avaliada sob a forma de área abaixo da curva de progresso da doença (AACPD). Procedeu-se a análise dialélica de acordo com o modelo de GRIFFING (1956). Observou-se existência de variabilidade genética aditiva entre os genitores e predominância de efeitos gênicos aditivos envolvidos na determinação da AACPD, além da existência de desvios de dominância bidirecional no controle do caráter em questão. A análise dialélica foi eficiente na seleção de genitores visando o pré-melhoramento da resistência à requeima, destacando os acessos BGH- 2117, BGH-2127 e BGH-2343 como os de maior frequência de alelos favoráveis e divergentes, por isso devem ser incluídos em cruzamentos visando o pré-melhoramento da resistência à requeima.
|
Page generated in 0.0407 seconds