Differences in cadmium uptake and accumulation in three soybean cultivars.

Three soybean (Glycine max) cultivars (Enrei, Tsurunoko, and Tsukui) were grown in a field with high concentrations (from 0.9 to 1.4 mg kg -1 dry weight (DW)) of soil cadmium (Cd) to investigate the differences in Cd uptake and accumulation. The soil was a Haplaquept that had been utilized for paddy rice with summer irrigation for more than 100 years. In Enrei, Cd accumulated throughout the plant, ranging from 42 µg plant -1 in the green seed (non-dry immature seed) stage 90-110 days after sowing to 32 µg plant-1 in the mature seed (the mature, dried seed) stage 130-150 days after sowing. The translocation of Cd to mature seeds increased rapidly after green seed formation. The order of Cd concentration in the green seeds was Enrei < Tsurunoko < Tsukui, with mean values s of 0.21, 0.27, and 0.42 mg kg -1 DW, respectively, and mature seeds with 0.27, 0.34, and 0.51 mg kg -1 DW, respectively. Most of these values were higher than the allowable limits that were presented in the Codex Committee on Food Additives and Contaminants until 2004. Although the soil Cd concentration determines the Cd concentrations in edible plants, the Cd increase in the soybean seeds was not directly related to the Cd content in the soil. This suggests that Cd uptake varies among soybean cultivars and that low-uptake cultivars should be developed to decrease Cd intake by consumers.