Effects of environment and genotype on mercury and methylmercury accumulation in rice (Oryza sativa L.)

Background and aims: Rice grains contaminated by mercury (Hg) and methylmercury (MeHg) pose risks to human health. This study evaluated the relative importance of genotype, environment and genotype-environment interactions on the accumulation of total Hg (THg) and MeHg in brown rice. Methods: A pot trial with four rice genotypes and 10 Hg-contaminated paddy soils was conducted under greenhouse conditions. The effects of genotype, environment and genotype-environment interactions on brown rice THg and MeHg accumulation were assessed by an Additive Main Effects and Multiplicative Interaction (AMMI) model. Results: THg and MeHg concentrations in brown rice ranged from 20.5 to 75.5 μg kg⁻¹ and 2.24 to 54.7 μg kg⁻¹, respectively. The AMMI model indicated that genotype explained 41.1 and 19.6%, environment described 40.6 and 55.8%, and the genotype-environment interaction explained 11.9 and 20.0% of the variation in brown rice THg and MeHg levels, respectively. Brown rice THg positively correlated with water-soluble Hg and total potassium, but negatively correlated with total sulphur, iron, total organic carbon and nickel in soils. Brown rice MeHg negatively correlated with soil pH and selenium. Conclusion: THg accumulation in brown rice was mainly affected by both genotype and environment, whereas MeHg accumulation was largely determined by environment.