Progresso genético para produção de grãos obtido em doze anos de melhoramento da população elite de arroz de terras altas
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2015-08-10
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Universidade Federal de Goiás
Resumo
The genetic improvement resulted from plant breeding acts decisively in maintaining the supply of
agricultural foods like rice. The contribution of this genetic improvement to increase productivity
is expressed in many crops by genetic progress which represents the genetic changes in the course
of the selection cycles, and promotes the advance of genotypic average towards selection. Among
the strategies adopted to increase the gain by selection, the early generation selection proves to be
promising. This work has aimed to evaluate the genetic potential for selecting upland rice
progenies and estimate the genetic progress for grain yield. The data used in this study were
obtained from the progeny yield trials conducted in the period of eleven agricultural years 2002/03
to 2012/13 conducted by Embrapa Rice and Beans. The traits analyzed were grain yield (kg ha-1),
plant height (cm) and days to flowering (day). In each year of the experiment, a group of progeny
was tested in four to six sites. It was used Federer's augmented block design without replication per
site in seven years and with at least three checks, in four years of the series were used two
replications. The experimental data within each year were submitted to joint analysis. A mixedeffects
linear model was applied for estimating the components of variance by the method of
restricted maximum likelihood (REML). From this estimate of the components, it was calculated
the genetic and phenotypic parameters, in addition the selective accuracy, the experimental
precision coefficient, the experimental variation coefficient and relative variation coefficient. The
genetic progress was estimated by the method of generalized linear regression of the adjusted
means of progeny groups evaluated in each year by the mixed model approach. The estimates of
the relative annual mean gain and the total relative gain for the three studied traits were also
obtained. The estimates of genetic variance among progenies for grain yield were highly
significant (p < 0.001), except for the progeny group evaluated in 2007. The heritability estimation
ranging from 0.22 to 0.69 that, associated with the selective accuracy, indicates the expected level
of efficiency with early generation selection in each group of progenies. For Plant height and daysto-
flowering, the genetic variance estimates were significant (p ≤ 0.01) in all groups. The variance
components for these traits led to a rather high heritability estimation that suggests favorable
conditions for selection in early generations. The genetic progress for grain yield (80.5 kg ha-1 yr-1)
was highly significant. This value represents a relative annual mean gain of 2.88%. Throughout the
period, the cumulative gain was estimated in 32.86% which indicates an increase of 918 kg ha-1 for
grain yield. The response for plant height was not significant, suggesting that the height of
progenies remained stable over the period. For days-to-flowering, it was detected significant
increase in cycle length, indicated by the cumulative increase of the vegetative period in about five
days (6.73%). From these results we conclude that early generation selection, adopted by the
breeding program, were effective in promoting the genetic gain for grain yield in the elite
populations.
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BARROS, M. S. Progresso genético para produção de grãos obtido em doze anos de melhoramento da população elite de arroz de terras altas. 2015. 59 f. Dissertação (Mestrado em Genética e Melhoramento de Plantas) - Universidade Federal de Goiás, Goiânia, 2015.