Seleção de linhagens de milho a partir do esquema de topcrosses com testadores recíprocos intergrupos

• Autor(a) principal: Costa, Nayana Valéria
• Data de Publicação: 2020
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UFG
• Texto Completo: http://repositorio.bc.ufg.br/tede/handle/tede/10504
• topic: Zea mays L.; Cruzamento dialélico; Depressão endogâmica; Variedades sintéticas; Predição de médias; Diallel crossing; Inbreeding depression; Synthetic varieties; Prediction of means; CIENCIAS AGRARIAS::AGRONOMIA

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.