Análises biométricas e mapeamento de QTLS para tolerância à seca em milho

• Autor(a) principal: Tomé, Lívia Gracielle Oliveira
• Data de Publicação: 2009
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/237
• topic: Milho; Interação genótipo por ambiente; Ganhos por seleção; Mapeamento de QTL; Tolerância à seca; Maize; Genotype x environment interaction; Gains with selection; QTL mapping; Drought tolerance; CNPQ::CIENCIAS BIOLOGICAS::GENETICA::GENETICA QUANTITATIVA

One of the major goals of crop improvement is the increase in agricultural productivity associated with the improvement for the consumption in human or animal feeding. These goals can be achieved through improvements in environmental conditions or by improving the genetic potential of populations. Recently, much has been discussed about global warming, climate change on the agricultural scenario in the face of these changes and the contribution of genetic improvement in mitigating the problems arising from global warming. Drought is a major environmental stresses that limit plant growth and consequently crop yields. Plants respond to water deficit and adapt to drought conditions through a variety of physiological and biochemical changes, including phenological changes. However, the losses in grain production in maize are severe when the crop is under water stress condition, which is one of the main limiting factors. Maize is particularly sensitive to water stress during the reproductive phase. National and international maize breeding programs, have considered the simultaneous study of (i) biometric analysis of traits related to drought and their correlation with grain yield and (ii) the use of molecular markers technology for detection of QTLs, which are the identification of genomic regions responsible for inducing tolerance to drought. Both studies make it possible for geneticists understand the inheritance of the tolerance to drought. The genetic investigations indicate that most of the traits related to abiotic stress have complex inheritance, controlled by several genes and highly influenced by environmental variation. This study aimed to address these two types of analysis for the study of an F2:3 maize population developed by Embrapa / Maize and Sorghum. The experiments conducted during 2006 and 2007 allowed us to estimate accurate inferences for both improvement and QTL mapping. Both approaches showed genetic variability for characteristics of interest, predicting the success of future studies and possible use in breeding programs. The genotype x environment interaction was predominantly complex, showed the need for the conduct and evaluation of segregating populations in different maize seasons (years) and in the water stress environment. The major gains with indirect selection for grain production are achieved in the prolificacy trait. However, the largest direct gains for grain production, in the water stress environment, are achieved based on the average performance of the genotypes. The QTL detection analysis allowed the generation of a linkage map with 82 microsatellite markers, covering 825.03 cM of the maize genome, with an average of one marker every 20 cM. Forty and five QTLs were mapped by the simple interval methodology: anthesis silking interval (six), plant height (thirteen), yield (six), leaf senescence (ten), prolificacy (five), and relative production (five).