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Mineral elements in brown rice grain play an important role in human health. In this study, variations in the content of iron (Fe), zinc (Zn), selenium (Se), cadmium (Cd), and lead (Pb) in 378 accessions of brown rice were investigated, and association mapping was used to detect the quantitative trait loci (QTLs) responsible for the variation. Among seven subpopulations, the mean values of Zn and Cd in the japonica group were significantly higher than in the indica groups. The population structure accounted for from 5.7% (Se) to 22.1% (Pb) of the total variation. Correlation analyses showed that Pb was positively correlated with the other minerals (P < 0.001) except for Se. For the five mineral elements investigated, 20 QTLs, including some previously reported and new candidate loci, were identified. Particularly, three cases of QTL colocalization, i.e. Cd and Pb on chromosome 5, Zn and Pb on chromosome 7, and Se and Pb on chromosome 11, were observed. This study suggested that the identified markers could feasibly be used to enhance desired micronutrients while reducing the heavy metal content in whole rice grain by marker-assisted selection (MAS).

Macro- and microelement contents are important traits for nutritional quality in rice. In this study, quantitative trait loci (QTLs) for the contents of seven mineral elements in milled rice were detected using recombinant inbred lines (RILs) of the indica rice cross Zhenshan 97/Milyang 46, followed by the validation and fine mapping of a QTL region on the short arm of chromosome 6. A total of 20 QTLs distributed on chromosomes 1, 3, 5, 6, 10, and 11 were detected in the RIL population. Co-localizations of QTLs for multiple traits were observed, of which the qP3/qMg3/qZn3 region was shown to have the largest effects for the contents of phosphorus, magnesium, and zinc, and the qK6.1/qCa6/qZn6/qMn6/qCu6 region was found to be responsible for five of the seven traits. Using near isogenic lines having sequential segregating region, the target QTL on chromosome 6 was delimitated to a 29.9 kb region flanked by RM19410 and Si2944. This QTL showed major effects for all seven traits, with the enhancing alleles derived from the male parent Milyang 46.