Identification of QTLs related to cadmium tolerance from wild rice (Oryza nivara) using a high-density genetic map for a set of introgression lines

Cadmium (Cd) is a toxic heavy metal that is harmful to human health. Oryza nivara, a wild rice species, serves as a germplasm pool for various favorable genes that can be used in cultivated rice. To detect quantitative trait loci (QTLs) and germplasm related to Cd tolerance in O. nivara, we analyzed one set of introgression lines with a high-density genetic map. Seven QTLs related to Cd tolerance were identified on chromosomes 2, 4, 6, and 8, and an allele of one locus (Bin774) from O. nivara affected two phenotypic traits and was able to increase Cd tolerance in rice. In a further analysis of GeneChip data released by the National Center for Biotechnology Information, we explored five candidate genes induced by Cd stress in the QTL region: two oxidoreductase genes (aldo-keto reductase genes LOC_Os04g27060 and LOC_Os04g26920); one terpene synthase gene (LOC_Os04g27190); one cysteine-rich receptor-like protein kinase gene (LOC_Os04g25060); and one serine carboxypeptidase homolog gene OsSCP23 (LOC_Os04g25560). One Cd-tolerant introgression line (Ra44) was also obtained, with a significantly higher survival rate under Cd stress (93.8%) compared to recipient parent 93-11 (2.3%). Identification of candidate genes and the Cd-tolerant introgression line Ra44 should facilitate further investigation of the mechanism of rice tolerance to Cd contamination.