Phytoextraction by rice capable of accumulating Cd at high levels: reduction of Cd content of rice grain.

In accordance with a new international standard set by the Codex Alimentarius Commission for cadmium (Cd) contentin rice grain, Japan must perform large-scale remediation of paddy fields polluted with lowto moderate levels of Cd. Phytoextraction using hyperaccumulating wild plants has been proposed as a low-cost, environmentally friendly restoration technology. However, because of difficulties with sowing, weed and disease control, and harvesting, hyperaccumulators may not be suitable for large-scale phytoextraction in polluted paddy fields. Here, we demonstrated phytoextraction using Indica-type rice cultivars capable of accumulating Cd at high levels. Phytoextraction with the Indica rice Chokoukoku grown for 2 years without irrigation after drainage removed 883 g Cd ha(-1), reduced the total soil Cd content by 38%, and reduced the grain Cd content in subsequently grown Japonica food rice by 47% without decreasing yield. The results suggest that phytoextraction with Chokoukoku can remove Cd from paddy fields polluted with low to moderate levels of Cd and reduce the grain Cd concentration of Japonica food rice cultivars to below the Codex standard within a reasonable time frame. This approach will help reduce the risk of Cd contamination of rice from paddy fields.