Ganhos genéticos após seis ciclos de seleção em três populações de cenoura

Abstract

The objective of this work was to evaluate the genetic gain with selection for root traits in three carrot populations. The experiment was conducted at Embrapa Hortaliças, Brasília -DF, Brazil. Three carrot populations derived from cultivar Brasília and of common origin until 2001, were selected in six consecutive generations in the summers of 1998 to 2003. In the summer of 2004, seed samples of each year were sowed in the field in a randomized block design with five replications and plots of 1m 2 . Ninety days after sowing, 25 roots per plot were harvested and evaluated for: length, xylem and phloem diameter, green shoulder length, mass, presence of halo, shape of tip and shoulder, and L* a* b* parameters of xylem and phloem. Analysis of variance, comparisons among treatment means and estimation of genetic gain with selection were performed. In the last six years of selection, visual selection for color traits was not successful, probably due the low genetic variability, because the roots of these populations are already deep in color, indicating higher β-carotene content. Increase in mass and root length was seen in both populations, with a proportional decrease in mean diameter of root and phloem. Aos 90 dias após o semeio, 25 raízes por parcela foram colhidas e avaliadas quanto ao comprimento, diâmetro do xilema e do floema, comprimento da extensão do ombro verde, massa, presença de halo, formato de ponta e de ombro e parâmetros L* a* e b* do xilema e floema. Foram realizadas análise de variância, e comparações de médias entre os tratamentos e calculados os ganhos genéticos com a seleção. Nos últimos seis anos de seleção, não foi possível obter êxito na seleção visual para os caracteres de cor, provavelmente devido à baixa variabilidade de ordem genética, visto que as raízes das populações já são bastante escuras, indicando grande quantidade de β-caroteno. Já para massa e comprimento de raiz, incrementos puderam ser verificados em ambas as populações, com proporcional decréscimo nas médias para os caracteres diâmetro de raiz e floema da raiz. Palavras-chave:Daucus carota L., progresso genético, melhoramento.

Direct selection for phenotypic traits in carrot genotypes

“…Estimated gains for root mass in this study are quite superior to real gains calculated by Silva & Vieira (2010) and Silva et al (2012a). In the first case, the authors obtained gains of 2.82% per selection cycle evaluating three carrot populations of Brasília group, selected on six selection cycles for traits which provided higher root productivity (thicker and longer roots).…”

Behavior of half-sib progenies of coriander

“…This selection method is widely used in the improvement of crosspollinated species. It allows an increase in the frequency of favorable alleles for the desired characters, in addition, to gains resulting from recurrent selection for different traits have been observed in studies performed with carrot Vieira, 2010), onion (CRAMER, 2006), and potato (BENITES; PINTO, 2011). Recurrent selection allows significant improvement of the evaluated traits.…”