Tese
Título	Estudos genéticos dos mecanismos para eficiência no uso de fósforo em linhagens de milho
Autor	Spolaor, Leandro Teodoski
Unidade	Pós-Graduação em Genética e Melhoramento
Área de Concentração	Genética e Melhoramento
Orientador	Carlos Alberto Scapim
Co-Orientador(es)	Carlos Albertp Scapim Ronal José Barth Pinto
Banca Examinadora	Leandro Simões Azeredo Gonçalves Josué Maldonado Ferreira Sylvia Morais de Sousa Luiz Fernando Pricinotto
Data de Defesa	24/07/2020
Resumo	O foco dos programas de melhoramento de milho tem sido em características da parte aérea das plantas, principalmente para aumentar a produção de grãos. No entanto, visando maior eficiência do uso de nutrientes tais como o fósforo (P), e considerando que as reservas de P que estão prontamente disponíveis para uso podem ser esgotadas, é necessário o desenvolvimento de genótipos com maior eficiência no uso desse nutriente, investindo, também, em características do sistema radicular. Diante disso, o objetivo do trabalho foi estudar os efeitos gênicos associados a características radiculares, agronômicas, e de eficiência em linhagens de milho em condições contrastantes de fósforo. Nos cruzamentos dialélicos foram utilizadas 10 linhagens de milho do banco de germoplasma da Universidade Estadual de Maringá (UEM), resultando em 45 híbridos, que foram avaliados a campo na Segunda Safra de 2018 em Dourados – MS e na safra 2018/19 e, na Segunda Safra de 2019 em Londrina – PR. O experimento em câmara de crescimento avaliou a massa seca da parte aérea e de raízes de cada tratamento utilizando solução nutritiva, em dois níveis de P (baixo e alto), quantificando também o teor de P nas plântulas. Foi observada uma ampla variabilidade genética para características relacionadas à eficiência no uso do P em condições de campo e em solução nutritiva. Em geral, as características relacionadas à eficiência no uso do P são controladas por genes de efeito aditivo e não aditivos; todavia, os genes de efeito aditivo são mais pronunciados em relação aos não-aditivos. Em contrapartida, os efeitos gênicos não-aditivos foram mais importantes para o rendimento de grãos em ambas as condições de P. Não foi observada correlação entre as características avaliadas em fase inicial (solução nutritiva) e final (condições de campo) de desenvolvimento do milho, indicando que diferentes genes e mecanismos morfofisiológicos atuam de forma distinta em ambos os estádios de desenvolvimento da planta. A identificação de genótipos eficientes e responsivos ao P é considerada uma as principais estratégias para redução da dependência de adubos fosfatos em sistemas de agricultura sustentáveis. The focus of corn breeding programs has been on the characteristics of the aerial part of plants, mainly to increase grain production. However, aiming at greater efficiency in the use of nutrients such as phosphorus (P) and considering that the reserves of P that are readily available for use can be depleted it is necessary to develop genotypes with greater efficiency in the use of this nutrient, also investing in in characteristics of the root system. Therefore, the objective of the work was to study the genetic effects associated with root, agronomic and efficiency characteristics in maize strains under contrasting phosphorus conditions. At diallel crosses, 10 maize strains from the germplasm bank of the State University of Maringá (UEM) were used, resulting in 45 hybrids, which were evaluated in the field in the second crop of 2018 in Dourados - MS and in the 2018/19 and second crop 2019 harvest in Londrina - PR. The growth chamber experiment evaluated the dry mass of the aerial part and roots of each treatment using nutrient solution in two levels of P (low and high), also quantifying the P content in the seedlings. A wide genetic variability was observed for characteristics related to the efficiency in the use of P in field and nutrient solution conditions. In general, the characteristics related to the efficiency in the use of P are controlled by genes with additive and non-additive effects; however, genes with an additive effect are more pronounced than non-additives. On the other hand, non-additive gene effects were more important for grain yield in both conditions of P. No correlation was observed between the characteristics evaluated in the initial (nutrient solution) and final (field conditions) of corn development, indicating that different genes and morphophysiological mechanisms act differently in both stages of plant development. The identification of efficient and P-responsive genotypes is considered one of the main strategies for reducing dependence on phosphate fertilizers in sustainable farming systems.
Palavras-chave	Zea mays L., Breeding Phosphate, fertilization Phenotyping
Title
Abstract	The focus of corn breeding programs has been on the characteristics of the aerial part of plants, mainly to increase grain production. However, aiming at greater efficiency in the use of nutrients such as phosphorus (P) and considering that the reserves of P that are readily available for use can be depleted it is necessary to develop genotypes with greater efficiency in the use of this nutrient, also investing in in characteristics of the root system. Therefore, the objective of the work was to study the genetic effects associated with root, agronomic and efficiency characteristics in maize strains under contrasting phosphorus conditions. At diallel crosses, 10 maize strains from the germplasm bank of the State University of Maringá (UEM) were used, resulting in 45 hybrids, which were evaluated in the field in the second crop of 2018 in Dourados - MS and in the 2018/19 and second crop 2019 harvest in Londrina - PR. The growth chamber experiment evaluated the dry mass of the aerial part and roots of each treatment using nutrient solution in two levels of P (low and high), also quantifying the P content in the seedlings. A wide genetic variability was observed for characteristics related to the efficiency in the use of P in field and nutrient solution conditions. In general, the characteristics related to the efficiency in the use of P are controlled by genes with additive and non-additive effects; however, genes with an additive effect are more pronounced than non-additives. On the other hand, non-additive gene effects were more important for grain yield in both conditions of P. No correlation was observed between the characteristics evaluated in the initial (nutrient solution) and final (field conditions) of corn development, indicating that different genes and morphophysiological mechanisms act differently in both stages of plant development. The identification of efficient and P-responsive genotypes is considered one of the main strategies for reducing dependence on phosphate fertilizers in sustainable farming systems.
Key-words	Zea mays L , Melhoramento genético, Adubação fosfatada, Fenotipagem
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