Number of recombinations and genetic properties of a maize population undergoing recurrent selection

Abstract

In maize recurrent selection programs, selected genotypes were recombined once to generate genetic variability for the next selection cycle. Selection generates negative gametic phase disequilibrium which reduces genetic variances, and this disequilibrium is not significantly reduced with only one generation of recombination. The objective of this research was to assess the effects of one additional generation of recombination on phenotypic and genotypic parameters in a maize population undergoing recurrent selection. Selected progenies of the EPB-4 population were subjected to one and two generations of recombination, and from each generation half-and full-sib progenies were developed and evaluated at three environments for grain yield, plant and ear heights, prolificacy, and ear placement. There were no significant changes between each progeny type with one and two generations of recombination for the means, ranges, phenotypic distribution of the traits, genetic variances, heritability coefficients, and genetic correlations for the traits assessed. The results suggest that an additional generation of recombination will not increase the effectiveness of maize recurrent selection programs. Key words: maize improvement, heritability coefficients, genetic correlations NÚMERO DE RECOMBINAÇÕES E AS PROPRIEDADES GENÉTICAS DE UMA POPULAÇÃO DE MILHO SOB SELEÇÃO RECORRENTERESUMO: Nos programas de seleção recorrente, os genótipos selecionados são recombinados uma vez para gerar variabilidade genética para o próximo ciclo de seleção. A seleção gera desequilíbrio negativo na fase gamética, reduzindo as variâncias genéticas, e este desequilíbrio não é significantemente reduzido com apenas uma geração de recombinação. O objetivo desta pesquisa foi avaliar os efeitos de uma geração adicional de recombinação sobre parâmetros fenotípicos e genéticos em uma população de milho submetida à seleção recorrente. Progênies selecionadas da população EPB-4 foram recombinadas por uma e duas gerações, e de cada geração foram obtidas progênies de meios-irmãos e de irmãos germanos, as quais foram avaliadas em três ambientes para produção de grãos, altura da planta e da espiga, prolificidade e posição da espiga. Não foram detectadas alterações significativas entre cada tipo de progênie com uma e duas gerações de recombinação para as médias, intervalos de variação, distribuição fenotípica dos caracteres, variâncias genéticas, coeficientes de herdabilidade e correlações genéticas para os caracteres avaliados. Os resultados sugerem que uma geração adicional de recombinação não aumentará a eficiência dos programas de seleção recorrente em milho. Palavras-chave: melhoramento de milho, coeficientes de herdabilidade, correlações genéticas

Four Parent Maize (FPM) Population: Effects of Mating Designs on Linkage Disequilibrium and Mapping Quantitative Traits

“…relationship among parents, the genetic architecture of traits, population size, and the extent of transgressive segregation) constant. Previous studies using narrow elite Midwestern germplasm have failed to show substantial or significant increases in variation from intermating (Lamkey et al, 1995; Lima Neto and Souza Júnior, 2009). However, it is unknown if intermating in parents derived from more diverse germplasm would expose greater transgressive segregation, although Mahan (2015) has shown that multiparent populations do show an advantage over biparental populations when working with genetically narrow parent lines.…”

Supporting Physiological Trait for Indirect Selection for Grain Yield in Drought-Stressed Popcorn

“…Conversely, indirect selection from the variables selected for GY prediction, such as TL and SPAD17, may possibly be used with no major negative influence on PE. Commonly, the genetic correlation of PR with GY is high, both under normal [ 50 ] as well as stress conditions [ 26 ]. Some studies have shown that, under water restrictions, the heritability for PR remained constant or even increased, opposite to the observations for grain yield [ 49 ], which may favor genetic gains by indirect selection for this trait.…”

Screening of Popcorn Genotypes for Drought Tolerance Using Canonical Correlations

“…Durães et al, 2004 [39] described that, in the pre-flowering period, the plants have already reached or are close to the end of the plant development. It should be stated that, in maize, PR presents a high genetic correlation with GY, both under adequate water conditions of growing [42] and under stress conditions [43], being used as a selection trait in breeding programs for WS conditions. SPAD index (leaf greenness), generated by the evaluation of a portable chlorophyll meter (SPAD), turned out to be a trait of high potential for genotypic discrimination in materials evaluated under different water conditions.…”