Seleção de linhagens de milho a partir do esquema de topcrosses com testadores recíprocos intergrupos
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2020-02-28
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Universidade Federal de Goiás
Resumo
The method of topcrosses with reciprocal intergroup testers allows the estimation
of genetic parameters and prediction of means of hybrids and synthetic varieties, without the
need for diallel crossing, which causes a reduction in the number of evaluated genotypes. The
objectives of the present study were: i) to evaluate heterosis components and combining
ability of two groups of maize S1 inbred lines derived from the UFG-Samambaia population; ii)
to improve the procedure for analyzing heterosis components based on the use of topcrosses
with reciprocal testers, including S2 inbred lines; iii) to predict the performance of synthetic
and hybrid that can be obtained from selected inbred lines. The experiment was carried out in
the experimental area of the School of Agronomy of the Universidade Federal de Goiás,
Goiânia-GO, with 60 S1 maize inbred lines derived from the UFG-Samambaia population,
where 30 presented dent kernels (Group A) and 30 presented flint kernels (Group B). From
the S1 inbred lines, 60 S2 inbred lines were obtained, 30 from group A and 30 from group B
and 57 hybrids, where 27 were from group A inbred lines crossed with a mixture of group B
inbred lines and 30 from group B inbred lines crossed with a mixture of group A inbred lines.
The genotypes were divided into six trials and were included three common control
treatments. A randomized block design with four replications was used and the variables
analyzed were: male (FM) and female (FF) flowering, flowering interval (IF), plant height (AP)
and ear height (AE), lodging and breaking (AQ), prolificacy (PROL), ears yield (PE) and grain
yield (PG). Analysis of variance was performed for the individual trials and based on
topcrosses. Parameter estimation and sum of squares of model effects were obtained from the
least squares method. The general combining ability (CGC) and inbreeding depression (DP)
were estimated from the effects of the model. The prediction of means for synthetics and
hybrids was performed using the lines that presented higher estimates of general combining
ability. The lines of the variety UFG-Samambaia presented genetic variability for the evaluated
traits. The additive effects were decisive for the manifestation of all traits, which points to the
possibility of genetic gain by recurrent selection. Most of the genotypes belonging to groups A
(dent kernels) and B (flint kernels) showed potential for extracting inbred lines for later
formation of hybrids. The dominance effects were more expressive for the traits related to
productivity and had a strong influence on the components of heterosis and inbreeding
depression. The inclusion of S2 inbred lines in the intergroup reciprocal topcrosses analysis
model was effective for detailing the additive and dominance effects. Estimates of general
combining ability pointed out the variability between inbred lines that can be used in the
selection of hybrids. Prediction methods allowed the selection of superior inbred lines for the
formation of synthetics with adequate productive potentials when crossed.
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COSTA, Nayana Valéria. Seleção de linhagens de milho a partir do esquema de topcrosses com testadores recíprocos intergrupos. 2020. 73 f. Dissertação (Mestrado em Genética e Melhoramento de Plantas) - Universidade Federal de Goiás, Goiânia, 2020.