Purpose

Soybean isoflavones (daidzein, genistein and glycitein and their conjugates) can have significant beneficial effects on human health by preventing cancer, lowering blood cholesterol, preventing osteoporosis and promoting vascular health.

Animal models have shown that soy products are more effective than isoflavone supplements. Generally, high isoflavone intake is beneficial for most humans. However, evidence shows that certain breast cancers are stimulated by isoflavones.

Therefore, developing ways to increase or decrease seed isoflavones to satisfy the needs of different consumer groups should enhance the already accepted value of soybean as an important functional food for humans.

Objective

Overall objective is to improve the health-promoting value of soybean, by manipulating (increasing or decreasing) seed isoflavone levels to give the ever-increasing number of soy food consumers a choice of better, more reliable products.

General Research

Germplasm has been identified with very high or low levels of isoflavones. Additional research on the critical combination of environmental and genetic factors will be determined and used in production of soybean seeds with high or low isoflavone levels. The enhanced germplasm will be used for commercial variety development.

The research team discovered from their two-year field and greenhouse studies, that temperature and water status has a profound influence on seed isoflavone levels in some genotypes. They also found that increased CO2 concentration also increased seed isoflavones.

Specific Research Objectives

1. Repeat the greenhouse experiment to confirm the initial results and determine which pathway enzymes control isoflavone accumulation during the seed filling period.
2. Examine the effects of elevated CO2 and ozone (O3) concentrations on isoflavone and other phenolic compound levels.
3. Screen additional edamame lines in the green bean stage for diversity of isoflavone content and composition and to investigate their responses to environmental differences.
4. To re-evaluate in different field locations the seed isoflavone content and composition of recently identified new accessions from the USDA soybean germplasm collection that show greater extremes than previously reported.

Impact

The new knowledge obtained in this study will allow us to be more effective in controlling isoflavone quantity and quality through genetics and selecting the optimum environment for modifying isoflavones.