Tran et al. 2024 — Arsenic and cadmium in 184 Vietnamese rice landraces (QTL mapping study)
This genome-wide association study (GWAS) characterized the natural variation in grain mineral accumulation across 184 Vietnamese rice landraces, reporting ICP-MS measurements of 23 elements including arsenic (As, reported as total arsenic by ICP-MS without speciation) and cadmium (Cd) in both brown and white rice grains. The study identified 27 significant QTL associations; 5 are for grain arsenic content and 2 for cadmium content. For As in brown rice, the mean was 0.16 ppm (SD 0.07; range 0.01–0.35), and for white rice, the mean was 0.11 ppm (SD 0.05; range 0.01–0.29). For Cd in brown rice, the mean was 0.21 ppm (SD 0.10; range 0.02–0.53), and in white rice, the mean was also 0.21 ppm (SD 0.10; range 0.01–0.53). High heritability was observed for both metals: H² ≥ 0.78 for As and ≥ 0.95 for Cd, indicating strong genetic control.
Key numbers
All values in ppm (mg/kg) dry weight, ICP-MS, brown rice (BR) and white rice (WR):
| Ion | Grain | Mean | SD | Min | Max | CV (%) | H² |
|---|---|---|---|---|---|---|---|
| As | BR | 0.16 | 0.07 | 0.01 | 0.35 | 43.75 | 0.78 |
| As | WR | 0.11 | 0.05 | 0.01 | 0.29 | 45.45 | 0.82 |
| Cd | BR | 0.21 | 0.10 | 0.02 | 0.53 | 47.62 | 0.95 |
| Cd | WR | 0.21 | 0.10 | 0.01 | 0.53 | 47.62 | 0.95 |
Note: As values are total arsenic by ICP-MS; no HPLC speciation was performed. Values should not be treated as inorganic arsenic (iAs). Li, B, Na, Ti, Cr, Se, and Pb concentrations were below the limit of quantification and are not reported.
Analytical method: ICP-MS (PerkinElmer NexION 2000, collision mode with He); 23 elements measured; pooled liquid reference material run every 9 samples for within-run correction; external calibration.
Methods (brief)
Field experiment in Vietnam growing 184 Vietnamese rice landraces. Grain samples (both brown and white rice from the same plants) ground and acid-digested (nitric acid + hydrogen peroxide, block heater at 115°C) then analyzed by ICP-MS. GWAS performed on BLUE values using 21,623 SNP markers with the BLINK model. QTL regions delimited by linkage disequilibrium (r² > 0.4). Candidate genes identified within QTL regions from MSU Rice Genome Annotation Project and RAPDB. Broad-sense heritability calculated as H² = (F−1)/F.
Implications
Certification: Vietnamese rice landraces show substantial genotypic variation in tAs and Cd accumulation, with up to 35-fold and 53-fold variation respectively within the landrace collection. This confirms that rice origin and variety are significant determinants of grain As and Cd content; HMT&C sourcing guidance should consider provenance.
Courses: Demonstrates that rice As/Cd accumulation is predominantly genetically controlled (high heritability), validating variety selection and agronomic provenance as risk mitigation strategies.
App: tAs and Cd occurrence data for Vietnamese rice landraces; documents the landrace-level variation range that informs ingredient risk estimation for rice-containing products.