Production and Environmental Influences on Soybean Isoflavone Type and Concentration

Abstract

Environmental conditions can have major impacts on the production of soybean [Glycine max (L.) Merr.] metabolites. In two studies, isoflavone type and concentration of soybean seed tissue was evaluated. Study one evaluated the effects of treatments with lactofen; weed control (WC) and white-mold suppression (WM) rates and timings of 217 g ai ha superscript -1 applied at the V1 stage and 122 g ai ha superscript -1 applied at the V5-R1 stages, respectively. Leaf tissue isoflavone concentration for post-lactofen treated leaf tissue was 26% higher for total soybean treated with WC than WM. Yield was unaffected by lactofen treatments, but double crop (DC) averages were ~16% higher than full season (FS). The highest concentrations of seed isoflavones for DC and FS were malonyldaidzin and malonylgenistin. The damage caused to the leaf tissue by lactofen applications did not result in a change in the seed isoflavone concentrations, individually or quantified as total isoflavone. While the Lactofen treatments did not show an effect on isoflavone type and concentration with respect to application timing for the seed tissue, the consistency of the relative isoflavone concentrations for seed are important for cultivar selection. The second study focused on cultivar differences and interaction with elevated tropospheric ozone concentrations. Four cultivars were grown in the field in open-top chambers and fumigated with either carbon filtered (CF) or ozone (O sub 3) enriched air. The two beta-glucosides, daidzin and genistin, and their Malonyl forms, plus one aglycone, genistein were present at detectable levels. The levels of the isoflavones daidzin, malonyldaidzin, malonylgenistin, and genistein were reduced for the seeds produced in O sub 3, 25, 19, 15, and 11%, respectively. Genistin levels were not significantly different, but the data did trend toward lower concentrations for the O sub 3 AQT. Genistein was the only aglycone detected. Williams 82 ranked consistently higher in levels of isoflavones, in some cases regardless of the AQT, than the other cultivars. Cultivar selection is important for the production of high isoflavone soybeans near urban centers. The affects of production and environmental influences on soybean seed isoflavone type and concentration are variable and should be evaluated independently. Total isoflavone concentration is the best measure of overall cultivar isoflavone production.