Submitted to: Cellular and Molecular Biology of Soybean Biennial Conference
Publication Type: Proceedings
Publication Acceptance Date: 8/31/2002
Publication Date: 8/20/2002
Citation: NELSON, R.L., LYGIN, A., LOZOVAYA, V., ULAOV, A., WIDHOLM, J. GENETIC AND ENVIRONMENTAL CONTROL OF SOYBEAN SEED ISOFLAVONE LEVELS AND COMPOSITION. CELLULAR AND MOLECULAR BIOLOGY OF SOYBEAN BIENNIAL CONFERENCE. 2002. p. 513. Interpretive Summary:
Technical Abstract: Soybean isoflavones are biologically active compounds that may have significant impact on human health. The objectives of this research are to identify genetic diversity in isoflavone quality and quantity in the seeds of selected U.S. cultivars and plant introductions (PIs) from the USDA Soybean Germplasm Collection and to determine the effects of environmental conditions on isoflavone concentration. From 400 PIs analyzed by HPLC for isoflavone concentration, 38 PIs in maturity groups II to IV selected for high or low isoflavone concentration and 31 U.S. cultivars released between 1953 and 2000 were grown at three locations in central Illinois in 2000 with two replications per location. Analysis of the variance revealed significant effects for entries, locations, and entry by location interactions for total isoflavones and amounts of diadzein and genistein. Only the entry effect was significant for glycitein concentration. Although the entry by location interaction was significant for total isoflavones, selecting the highest or lowest 10 entries at anyone location would have identified the five highest or lowest entries based on overall means. Introductions were identified with significantly higher or lower isoflavone content than any U.S. cultivar tested. Later maturity is generally associated with higher levels of isoflavones but entries with similar maturity dates can differ in total isoflavone content by more than four folds. The composition of the isoflavones differed significantly among entries. Mean diadzein percentage of total isoflavones varied from 30 to 52; genistein varied from 27 to 37; and glycitein ranged from 14 to 32. To better understand the environmental effects on isoflavones, we grew five entries with large genetic differences in isoflavone concentration in a greenhouse experiment in the Plant Care Facility at the University of Illinois. Soybean plants were grown under optimal night/daytime temperatures of 18/28 degree C with sufficient water. At approximately the R6 growth stage, the plants were placed less than three different night/day temperature regimes: optimal (18/28 degree C), sub-optimal (13/23 degree C), and super-optimal (23/33 degree C) and half the plants received optimal or approximately 30 percent of optimal water supply under each of three temperature conditions. All classes of isoflavones decreased as air temperature increased but the differences for diadzein and genistein were much greater than those from glycitein. The same pattern was true for differences in soil moisture with well-watered plants producing more isoflavones. Entries by treatment interactions were also significant. For some cultivars the imposition of drought stress lowered isoflavone levels by more than 50 percent whereas changes for other entries were less than 5 percent. Similar responses were noted for increases in air temperature.