Quantitative trait loci mapping for cadmium and microelements accumulation in rice using recombinant inbred lines

Cadmium (Cd) contamination in Oryza sativa L. rice grain poses a significant food safety risk. Cd uptake in rice occurs via transmembrane proteins that also transport divalent metal microelements such as iron (Fe), manganese (Mn), copper (Cu), and zinc (Zn). Identifying stable quantitative trait loci (QTLs) for Cd across different environments, along with co-localized QTLs for Cd and other elements, is crucial for understanding the genetic mechanisms of low Cd accumulation and facilitating fine mapping and gene cloning. A recombinant inbred line (RIL) population derived from D62B (a Cd-safe rice line) × Wujin4B (a high-Cd-accumulating rice line) was used to identify QTLs associated with Cd, Fe, Mn, Cu, and Zn accumulation. QTL mapping was conducted in three distinct environments to assess locus stability. A total of 61 QTLs were identified, including 23 QTLs related to Cd and 38 QTLs associated with other microelements. Two novel and stable QTLs for Cd (qLCA1 and qLCA12) were consistently detected across different environments, significantly reducing Cd concentration in brown rice and Cd translocation within the plant. Additionally, a previously unreported co-localized QTL (qCdA-4/qCuA-4) was identified, which significantly reduced both Cd and Cu accumulation in whole plants. This study identified two novel and stable QTLs for Cd (qLCA1 and qLCA12) that consistently reduced Cd concentration in brown rice and Cd translocation across different environments. Additionally, a newly discovered co-localized QTL (qCdA-4/qCuA-4) was found to regulate both Cd and Cu accumulation.