Agronomic performance of recombinant inbred line populations segregating for isoflavone content 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(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 microgram g(-1)) were identified with yields (4222 kg ha(-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 isoflavone and protein content ranging from 1746 to 1851 microgram g(-1) and 431 to 442 g kg(-1), respectively. It was possible to develop soybean with desirable isoflavone content in the seed and superior agronomic and seed quality traits.