Potencial de produtividade e variabilidade de populações semiexóticas de milho como base para seleção
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Data
2018-04-27
Autores
Mendes, Udenys Cabral
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Universidade Estadual Paulista (Unesp)
Resumo
O melhoramento genético de uma espécie alógama como o milho, pode ser dirigido essencialmente visando duas alternativas: a obtenção de populações melhoradas, ou a obtenção de uma geração F1 com vigor de híbrido. No caso de melhoramento de populações ocorre a oportunidade de incorporar novas fontes de germoplasma. de particular interesse por representar resultado de seleção específica para doenças foliares e outros caracteres.Germoplasma exótico (incluindo acessos do Brasil e de outros países) é aquele que não pertence à base genética comumente em uso no melhoramento, podendo assim contribuir com novos alelos que resultarão em aumento da variabilidade genética útil para o melhoramento. Os objetivos do trabalho foi verificar o valor genético-agronômico dos compostos recém sintetizados, o efeito depressivo da endogamia e inferir sobre a viabilidade de um programa de seleção recorrente visando o melhoramento intrapopulacional. Foram avaliadas as populações NAP-FA x HG-71, NAP-FL x HG-49, NAP-FB x HG-49 e NAP-DB x HG-49, com dois níveis de endogamia (S0 e S1), no sistema de macroparcelas, e 100 progênies de irmãos germanos e 50 progênies endogâmicas S1 das populações NAP-FA x HG-71 e NAP-DB x HG-49. Nas duas situações os experimentos foram delineados em blocos casualizados com três repetições em três e dois locais respectivamente. Foram avaliados os caracteres florescimento masculino e feminino, altura da planta e da espiga, comprimento e diâmetro de espiga, resistência a doenças foliares, acamamento, quebramento, espigas gessadas e produtividade de grãos. Foram estimados os parâmetros herdabilidade no sentido amplo e restrito, ganho com a seleção e correlação genotípica e fenotípica entre os caracteres. As populações apresentam bom potencial de produtividade de grãos, valor para melhoramento visando a introgressão de diferentes fontes de germoplasma no sistema de melhoramento e possuem elevado valor genético, tanto para produtividade como para outros caracteres agronômicos de interesse. As progênies de irmãos germanos com produtividade de grãos de 67,4%, 61,7%, 51,3% e 84,65% em relação às testemunhas nas duas localidades respectivamente, indicam a viabilidade da introgressão de germoplasma no sistema de melhorameto. As progênies S1 apresentam variabilidade suficiente para serem exploradas em programas de seleção recorrente. Os resultados também indicaram a existência de progênies com menor depressão por endogamia, que podem ser exploradas em programas de seleção interpopulacional e para extração de linhagens.
Genetic improvement of an allogamous specie such as maize, can be directed essentially towards two alternatives: obtaining improved populations or obtaining an F1 generation with hybrid vigor. In the case of population improvement there is an opportunity to incorporate new sources of germplasm with particular interest because it represents a result of specific selection for foliar diseases and other characters. Exotic germplasm (including access from Brazil and other countries) is one that does not belong to the genetic base commonly used in breeding, thus contributing with new alleles that will result in increased genetic variability useful for breeding. The objectives of the study were to verify the genetic and agronomic value of the newly synthesized composites, the depressive effect of inbreeding and to infer about the viability of a recurrent selection program aiming at intrapopulation improvement. Were evaluated the populations NAP-FA x HG-71, NAP-FL x HG-49, NAP-FB x HG-49 and [NAP-DB x HG-4], with two levels of inbreeding (S0 and S1) in macro plots system and 100 progenies of full-sibs and 50 endogamous progeny S1 from the NAP-FA x HG-71 and NAP-DB x HG-49 populations. In both situations, the experiments were in randomized blocks with three replicates in three and two locations respectively. The flowering characteristics of male and female, plant height, ear height, ear length, ear diameter, resistance to foliar diseases, lodging, breakage, ears bada granades and grain yield. Were estimates parameters heritability in the broad and restricted sense, gain with selection and genotypic and phenotypic correlation between the characters. The populations present good potential of grain yield, value for improvement aiming at the introgression of different sources of germplasm in breeding system and have high genetic value, both for productivity and for other agronomic traits of interest. The progenies of full-sibs with grain yield of 67,4%, 61,7%, 51,3% and 84,65% in relation to the check in two locations respectively, indicate the viability of the introgression of germplasm in the breeding system. The S1 progenies presented sufficient variability to be explored in recurrent selection programs. The results also indicated the existence of progenies with lower inbreeding depression, which can be explored in populations selection programs and and extraction of inbred lines.
Genetic improvement of an allogamous specie such as maize, can be directed essentially towards two alternatives: obtaining improved populations or obtaining an F1 generation with hybrid vigor. In the case of population improvement there is an opportunity to incorporate new sources of germplasm with particular interest because it represents a result of specific selection for foliar diseases and other characters. Exotic germplasm (including access from Brazil and other countries) is one that does not belong to the genetic base commonly used in breeding, thus contributing with new alleles that will result in increased genetic variability useful for breeding. The objectives of the study were to verify the genetic and agronomic value of the newly synthesized composites, the depressive effect of inbreeding and to infer about the viability of a recurrent selection program aiming at intrapopulation improvement. Were evaluated the populations NAP-FA x HG-71, NAP-FL x HG-49, NAP-FB x HG-49 and [NAP-DB x HG-4], with two levels of inbreeding (S0 and S1) in macro plots system and 100 progenies of full-sibs and 50 endogamous progeny S1 from the NAP-FA x HG-71 and NAP-DB x HG-49 populations. In both situations, the experiments were in randomized blocks with three replicates in three and two locations respectively. The flowering characteristics of male and female, plant height, ear height, ear length, ear diameter, resistance to foliar diseases, lodging, breakage, ears bada granades and grain yield. Were estimates parameters heritability in the broad and restricted sense, gain with selection and genotypic and phenotypic correlation between the characters. The populations present good potential of grain yield, value for improvement aiming at the introgression of different sources of germplasm in breeding system and have high genetic value, both for productivity and for other agronomic traits of interest. The progenies of full-sibs with grain yield of 67,4%, 61,7%, 51,3% and 84,65% in relation to the check in two locations respectively, indicate the viability of the introgression of germplasm in the breeding system. The S1 progenies presented sufficient variability to be explored in recurrent selection programs. The results also indicated the existence of progenies with lower inbreeding depression, which can be explored in populations selection programs and and extraction of inbred lines.
Descrição
Palavras-chave
Endogamia, Irmãos germanos, Melhoramento intrapopulacional, Seleção recorrente, Zea mays, Endogamy, Full-sibs, Intrapopulation improvement, Recurrent selection