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Dietary intake of isoflavones has been shown to reduce the risk of several major diseases in humans. Therefore, breeding soybean [Glycine max (L.) Merrill] seeds with desirable isoflavone content would be beneficial to the food and health industries, but the environmental sensitivity of the trait complicates phenotypic selection. The objective of this study was to identify quantitative trait loci (QTL) and epistatic interactions associated with isoflavone contents in soybean seeds. A population of 207 [F.sub.4:6] recombinant inbred lines (RILs) was produced from the cross 'AC756' x 'RCAT Angora'. The population was phenotyped at two locations in Ontario, Canada, and genotyped by means of 99 polymorphic SSR markers. A significant genotype x environment interaction was found. Seventeen QTLs were detected (P < 0.01) by single-factor ANOVA. Individual loci explained up to 10.5% (P < 0.0001) of the phenotypic variation. Interval mapping and composite interval mapping identified nine genomic regions (LGs A1, C2, D1a, F, G, H, J, K, and M) associated with isoflavone contents. Some QTL associated with agronomic or seed quality traits mapped to the same regions as those for individual isoflavone contents on LGs A1, C2, F, J, K, M, and N. Twenty-three epistatic interactions were detected for isoflavones. Multiple locus models explained up to 25.0% (P < 0.0001) of the phenotypic variation without epistasis and up to 35.8% (P < 0.0001) with it. The QTL identified in this study could be useful for developing soybean varieties with desirable isoflavone content in the seed through marker-assisted selection (MAS)., SOYBEAN has been mainly cultivated for the oil and protein content of the seed. In recent years, isoflavones have received considerable attention because of their high concentration in soybean seeds [...]

Soybean [Glycine max (L.) Merrill] seeds contain isoflavones, which have been associated with positive health effects in human adults but a negative effect on infants. Increasing or decreasing isoflavone content in the seed would be desirable; however, it is not known what impact this would have on agronomic and other seed quality traits. The main objective of this study was to determine if isoflavone content in soybean seeds was associated with changes in agronomic and seed quality traits. Recombinant inbred lines (RILs) with 'high' (n = 35), 'intermediate' (n = 35), and 'low' (n = 35) isoflavone content, were selected from three [F.sub.4:5] populations grown in 2000 and planted at three locations in southern Ontario in 2002. There were significant differences among populations, environments, and their interaction for isoflavone content. 'High' and 'low' phenotypic classes were significantly different for maturity in all three populations. Despite a positive correlation between yield and isoflavones, several RILs with decreased isoflavone content (970 µg [g.sup.-1]) were identified with yields (4222 kg [ha.sup.-1]) comparable to high-yielding cultivars. Isoflavone content had minimal effects on oil content, seed quality, and weight. Population 1 showed a significant negative association between isoflavone and protein content, whereas Pop. 2 and Pop. 3 did not. RILs were identified with high isofiavone and protein content ranging from 1746 to 1851 µg [g.sup.-1] and 431 to 442 g [kg.sup.-1], respectively. It was possible to develop soybean with desirable isoflavone content in the seed and superior agronomic and seed quality traits., ISOFLAVONES are secondary metabolites synthesized by 2-hydroxyisoflavanone synthase (IFS) and are found almost exclusively in legumes (Heller and Forkmann, 1994). Two IFS genes (IFS1 and IFS2) encoding functional proteins have [...]

Decreasing the palmitic and linolenic acid content of soybean [Glycine max (L.) Merrill] oil would help improve its nutritional quality and oxidative stability. The altered fatty acid profile in soybean germplasm lines with decreased levels of palmitic and linolenic acid have been developed at the University of Guelph, Canada, by combining different mutant alleles through hybridization. The objectives of this study were to determine the inheritance and interaction of palmitic and linolenic acid levels in RG3 and RG1, and the effects of these altered fatty acid levels on other fatty acids. RG3 and RG1 (low palmitic ≅ 45 g [kg.sup.-1] and linolenic ≅ 40 g [kg.sup.-1]) were crossed reciprocally to several soybean lines with altered or normal fatty acid profiles. Analysis of the reciprocal [F.sub.2] generations indicated no maternal or cytoplasmic effects for palmitic or linolenic acid content. Chi-square analyses of the [F.sub.2] generation demonstrated that RG3 and RG1 contained two alleles, fap1 and fapx, that controlled palmitic acid content. In addition, RG1 had a third allele, fan, which reduced its linolenic acid content. Calculation of gene substitution values indicated additive gene action at the fap1 and fan loci, whereas the fapx locus involved partial dominance. Correlation coefficients indicated no association between palmitic and linolenic acid. Decreases in palmitic and linolenic acid content were associated primarily with increases in linoleic acid content. Since fap1, fapx, and fan were inherited independently of each other and appeared to behave in an additive manner, RG3 and RG1 can be used in breeding programs as additional valuable sources of germplasm with altered fatty acid profiles., SOYBEAN is the most widely grown source of edible oil for human consumption. It is consumed predominantly in the form of margarine, shortening, and salad and frying oils. Palmitic acid [...]

There has been a major effort to produce soybean [Glycine max (L.) Merr.] lines with modified fatty acid profiles in order to improve quality and develop new uses for soybean oil. Utilization of the lines depends on their agronomic traits and stability of the fatty acid profiles in diverse environments. The objectives of this study were to (i) evaluate the influence of years and locations on the fatty acid composition of soybean genotypes with unique fatty acid profiles, (ii) determine which fatty acids and fatty acid profiles are the most stable, and (iii) evaluate agronomic and seed quality traits of mutant soybean lines. Genotypes were evaluated over three years (1996, 1997, and 1998) at four locations in Southern Ontario, Canada. Year effects had the largest impact on all fatty acid levels. Location effects were significant only for oleic and linolenic acids. Genotype x year interaction effect was significant for all fatty acids whereas genotype x location and genotype x year x location interaction effects were significant only for oleic, linoleic, and linolenic acids. Mutants with reduced or elevated palmitic, elevated oleic, or reduced linolenic acid concentrations exhibited average or higher stability than lines with normal levels of these fatty acids. Therefore, these lines may be suitable for growing in a wide range of environments. Maturity, plant height, lodging, seed size, and seed quality were significantly different between mutants and cultivars. Seed yield was significantly reduced in mutants compared to cultivars., THE END USE OF SOYBEAN [Glycine max (L.) Merr.] oil is influenced by its fatty acid composition. The seed oil of common soybean cultivars consists of ≅ 110 g [kg.sup.-1] [...]