Detection of a QTL for accumulating Cd in rice that enables efficient Cd phytoextraction from soil

Phytoextraction by high-cadmium (Cd)-accumulating rice (Oryza saliva L.) cultivars has been proposed as an attractive technique for cleaning up Cd-contaminated paddy field soil. To breed rice cultivars useful for Cd phytoextraction, it is necessary to understand the genetic basis of Cd accumulation in aerial parts. We developed backcross inbred lines (BILs) derived from a cross between a low-Cd-accumulating cultivar, Koshihikari (japonica), and a relatively high-Cd-accumulating cultivar, Jarjan (indica). The BILs were grown in fields containing two low levels of Cd and in pots of soil containing a moderate level of Cd. A quantitative trait locus (QTL) analysis revealed that a major QTL, qCdp7 (QTL potentially useful for Cd-phytoextraction on chromosome 7) contributed to accumulation of Cd in both brown rice and straw of plants grown in any of the three soils, and it accounted for 31% to 54% of the phenotypic variance. To confirm the phytoextraction-promotion ability of qCdp7, we grew BILs carrying the Jarjan allele of qCdp7 in Cd-contaminated soil, and confirmed the reduction of the Cd concentration in the shoots of Koshihikari subsequently grown in the phytoextracted soil. These results demonstrate that the Jarjan qCdp7 allele is effective at phytoextracting Cd from the soil.