Phytoextraction by high-Cd-accumulating rice to reduce Cd in wheat grains grown in Cd-polluted fields

Abstract

Phytoextraction using indica rice plants (Indian Rice Oryza ssp.) is a promising technique for remediating cadmium (Cd)-polluted paddy fields. Because this technique has only been established for paddy fields, we decided to examine phytoextraction in upland fields that have been converted from paddy fields. Although "CHOKOUKOKU" shows a shattering habit and lodging, its Cd uptake was significantly higher than that of other indica rice varieties. On the other hand, "IR8", which was able to accumulate only moderate levels of Cd in its shoots, has a lodging tolerance, making it an optimal variety for southwest Japan, which experiences several typhoons each year. Therefore, both "CHOKOUKOKU" and "IR8" were useful in estimating practical phytoextraction in upland fields. A practical phytoextraction examination showed that the total Cd uptake of "CHOKOUKOKU" and "IR8" was 822 and 545 g ha , respectively, after a 4-year period. After phytoextraction by planting high Cd-accumulating rice plants, the Cd concentration of the plot soil decreased by approximately 35%, compared to the initial Cd concentration. To evaluate phytoextraction efficiency in the upland field, wheat (Triticum aestivum) was subsequently grown in the remediation field. The Cd concentration in the grains of "SHIROGANEKOMUGI" grown in the phytoextraction plot was lower than that grown in a non-phytoextraction plot; regrettably, it exceeded the Codex Alimentarius Commission standard, whereas the grain Cd concentrations of "CHUGOKU165" planted in phytoextraction plots complied with the Codex standard for wheat grain. These results suggest that phytoextraction using high Cdaccumulating rice varieties is a practical remediation system for low Cd-polluted upland fields. Moreover, we determined the end point of the phytoextraction process, which occurs when the soil Cd concentration of the phytoextraction fields is less than 0.6 mg kg −1 if "CHUGOKU165" is cultivated in this area.

How Does Contamination of Rice Soils with Cd and Zn Cause High Incidence of Human Cd Disease in Subsistence Rice Farmers

“…3 Effect of alternate wetting and drying flood management on accumulation of As and Cd in rice grain [79]. The water management varied from traditional full season flood, through alternative wetting and drying, to furrow irrigation only when the soil reached 40 or 60 % of water holding capacity significant removal of Cd from the field [42,86]. Another gene, HMA2, is involved in translocation of Cd and Zn from roots to shoots [87,88], and yet another (LCT1) may affect low affinity Cd transport from leaves into grains [89].…”

Breeding and characterization of the high cadmium-accumulating rice line ‘Akita 119’

“…‘Cho-ko-koku’, ‘Jarjan’, and ‘Anjana Dhan’ accumulate significantly higher levels of Cd in their shoots and grains than do other cultivars grown worldwide ( Uraguchi et al 2009 ). After 2–4 years’ cultivation of ‘Cho-ko-koku’, the Cd concentration in the soil and grains of subsequent cultivars were reported to be lower than the levels in a control field ( Ibaraki et al 2009 , 2014 , Murakami et al 2009 ). These results indicate that high-Cd-accumulating rice cultivars are effective for Cd phytoremediation.…”

The Road to Practical Application of Cadmium Phytoremediation Using Rice

“…Within WRC, ‘Jarjan’ ‘Anjana Dhan’, and ‘Cho-ko-koku’ accumulated a significantly high level of Cd in the shoots and grains [ 13 ]. Cd uptake by ‘Cho-ko-koku’ was higher than ‘IR-8’ even in the field, and the Cd concentration in the field soil and grains of subsequent cultivars decreased more than those in the control field after the cultivation of ‘Cho-ko-koku’ for 2 or 4 years [ 19 , 20 ]. Phytoremediation capacity of Cd removal from soil depends on Cd concentration in the aerial parts and biomass of the plants.…”