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URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/11845

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    Detection and mapping of a lethal locus in a eucalyptus hybrid population
    (Pesquisa Agropecuária Brasileira, 2011-09-13) Rosado, Tatiana Barbosa; Tomaz, Rafael Simões; Rocha, Rodrigo Barros; Rosado, Antônio Marcos; Alves, Alexandre Alonso; Araújo, Elza Fernandes de; Alfenas, Acelino Couto; Cruz, Cosme Damião
    The objective of this work was to verify the existence of a lethal locus in a eucalyptus hybrid population, and to quantify the segregation distortion in the linkage group 3 of the Eucalyptus genome. A E. grandis x E. urophylla hybrid population, which segregates for rust resistance, was genotyped with 19 microsatellite markers belonging to linkage group 3 of the Eucalyptus genome. To quantify the segregation distortion, maximum likelihood (ML) models, specific to outbreeding populations, were used. These models consider the observed marker genotypes and the lethal locus viability as parameters. The ML solutions were obtained using the expectation‑maximization algorithm. A lethal locus in the linkage group 3 was verified and mapped, with high confidence, between the microssatellites EMBRA 189 e EMBRA 122. This lethal locus causes an intense gametic selection from the male side. Its map position is 25 cM from the locus which controls the rust resistance in this population.
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    Detection of QTL associated with rust resistance using IBD-based methdologies in exogamic Eucalyptus spp. populations
    (Crop Breeding and Applied Biotechnology, 2010-12) Rosado, Tatiana Barbosa; Tomaz, Rafael Simões; Ribeiro Junior, Marcio Fernandes; Guimarães, Lúcio Mauro da Silva; Araújo, Elza Fernandes de; Alfenas, Acelino Couto; Cruz, Cosme Damião; Rosado, Antônio Marcos
    In Brazil the rust caused by Puccinia psidii Winter stands out as the most important disease of eucalyptus. The use of resistant genotypes is the main control method, which makes the detection of markers linked to rust resistance essential to the selection of resistant genotypes. In this study, an F1 progeny of 131 plants from interspecific crossings of Eucalyptus was used to identify markers linked to resistance genes for this pathogen. An integrated map was constructed for linkage group three based on microsatellite markers. For QTL mapping two methodologies based on alleles identical-by-descent (IBD) were used: single marker analysis of Haseman and Elston and the interval mapping procedure of Fulker and Cardon. Both methods showed significant association for the Embra 125 marker.The QTL that explained 42 % of the phenotypic variation was mapped to 0.02 cM of this marker by the Fulker and Cardon. Marker Embra 125 has potential use in assisted selection, thus increasing the efficiency of the selection of resistant genotypes.
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    A priori choice of hybrid parents in plants
    (Genetics and Molecular Research, 2004-09-30) Dias, Luiz Antônio dos Santos; Picoli, Edgard Augusto de Toledo; Rocha, Rodrigo Barros; Alfenas, Acelino Couto
    Plant breeding deals with high-yielding genotypes. However, how best to choose parents of these genotypes remains an unsolved question. Here, we focus on a priori choice based on parental distances by means of agronomic and molecular data. Despite numerous theoretical and empirical studies, a priori choice continues to be a controversial procedure. Both success and failure are commonly reported. We looked at these ambiguous results in order to investigate their possible causes. A total of 139 articles on genetic divergence were sampled to examine aspects such as type and number of markers utilized. We suggest that the mean number of 160, 281 and 25 for RAPD and RFLP markers, and SSR loci, respectively, which we found in these papers, should be increased for accurate analysis. A second sample composed of 54 articles was used to evaluate the divergence-heterosis association. Most of them (28) detected positive divergence-heterosis association, whereas 26 revealed negative or inconclusive results. We examined several causes that influence a priori choice positively and negatively.