Genetical and environmental analyses of yield in six biparental soybean crosses

Abstract

-The yearly genetic progress obtained by breeding for increased soybean yield has been considered acceptable worldwide. It is common sense, however, that this progress can be improved further if refined breeding techniques, developed from the knowledge of the genetic mechanisms controlling soybean yield, are used. In this paper, data from four cultivars and/or lines and their derived sets of F2, F3, F7, F8, F9 and F10 generations assayed in 17 environments were analyzed to allow an insight of the genetic control of soybean yield under different environmental conditions. The general picture was of a complex polygene system controlling yield in soybeans. Additive genetic effects predominated although dominance was often found to be significant. Complications such as epistasis, linkage and macro and micro genotype x environment (G x E) interactions were also commonly detected. The overall heritability was 0.29. The relative magnitude of the additive effects and the complicating factors allowed the inference that the latter are not a serious problem to the breeder. The low heritability values and the considerable magnitude of G x E interactions for yield, however, indicated that careful evaluation through experiments designed to allow for the presence of these effects is necessary for successful selection.Index terms: Glycine max, genetic control, selection, polygenes, genotype environment interaction, breeding methods.ANÁLISE GENÉTICA E AMBIENTAL DA PRODUTIVIDADE DA SOJA EM SEIS CRUZAMENTOS BIPARENTAIS RESUMO -O progresso genético obtido para produtividade em soja é mundialmente considerado razoável. Entretanto, acredita-se que esse progresso possa ser significativamente aumentado se forem usadas técnicas refinadas de melhoramento, desenvolvidas a partir do melhor conhecimento do controle genético e do ambiente sobre a produtividade. Foram analisados, neste trabalho, os dados referentes a quatro linhagens ou cultivares e as populações descendentes F2, F3, F7, F8, F9 e F10, obtidos em ensaios realizados em 17 ambientes, para permitir uma avaliação dos efeitos genéticos controladores da produtividade na soja. Os efeitos genéticos aditivos predominaram, e foram detectados níveis significativos de dominância, em várias oportunidades. Também foram freqüentemente detectados efeitos genéticos, como: epistasia, ligação gênica e interações entre genótipo e ambiente. A herdabilidade no sentido restrito foi de 0,29. As análises mostraram que, em geral, o controle genético da produtividade da soja é realizado por poligenes com efeitos aditivos. A magnitude dos fatores complicadores comparativamente à dos efeitos aditivos permite prever que eles não representarão problema num programa de melhoramento. Entretanto, a baixa herdabilidade do carácter e os consideráveis níveis de interação entre genótipo e ambiente exigem que a avaliação da produtividade seja criteriosamente realizada para haver progresso genético por seleção.Termos para indexação: Glicyne max, controle genético, seleção, poligenes, interação genótipo-ambie...

POD NUMBER AND PHOTOSYNTHESIS AS PHYSIOLOGICAL SELECTION CRITERIA IN SOYBEAN (Glycine max L. Merrill) BREEDING FOR HIGH YIELD

“…The value of h 2 for TSW was comparable with that found for soybean grain yield (29%) by Toledo et al (2000) working with six crosses in 17 environments. An increase in the average seed yield (39%) and pod number (77%) of F3 lines compared with F2 lines was found following the selection of F2 lines based on pod number to generate F3 lines.…”

“…This method of selection limits the opportunity of best lines or genotypes to be selected in term of high pod number and photosynthetic rate. This is based on the low heritability of seed yield in general at the early filial generations in combination with a high rate of interaction between genetic and environmental factors (Toledo et al, 2000). The approach of genetic engineering at molecular level is a powerful way of generating genetic diversity that would complement classical breeding.…”

Epistasia para a produção de grãos em soja

“…(TOLEDO et al, 2000;VALERIO et al, 2005). E m s o j a e x i s t e m p o u c o s t r a b a l h o s n a literatura relacionados ao estudo da epistasia.…”

Heritability estimation in early generations of two-way crosses in soybean

“…Many soybean researches have been done on broad and narrow sense heritability estimates (AZEVEDO FILHO et al, 1998;TOLEDO et al, 2000;FARIAS NETO and VELLO, 2001;ROSSMAN, 2001;REIS et al, 2002), though few of them have been done using parentoffspring regression, among which is an oat and a soybean study (CABRAL et al, 2001;MUNIZ et al, 2002).…”