Genotypic variation in the tolerance to moderate cadmium toxicity among 20 maize genotypes with contrasting root systems

BACKGROUND: Cadmium (Cd) contamination in farmland is a serious environmental and safety issue affecting plant growth, crop productivity and human health. This study aimed to investigate genotypic variation in root morphology and Cd accumulations under moderate Cd stress among diverse maize genotypes. Twenty maize genotypes with contrasting root systems were assessed for Cd tolerance 39 days after transplanting (V6, six-leaf stage) under 20 μmol L–1 CdCl2 using a semi-hydroponic phenotyping platform in a glasshouse. Cadmium stress significantly inhibited plant growth across all genotypes.

RESULTS: Genotypic variation in response to Cd toxicity was apparent: shoot dry weight varied from 0.13 (genotype NS2020) to 0.35 g plant–1 (Dongke301) with deductions up to 63% compared to non-Cd treatment (CK). Root dry weight ranged from 0.06 (NS2020) to 0.18 g plant–1 (Dongke301) with a deduction up to 56%. Root length ranged from 2.21 (NS590b) to 9.22 m (Dongke301) with a maximal decline of 76%. Cadmium-treated genotypes generally had thicker roots with average diameter increased by 34% compared to CK. Genotypes had up to 3.25 and 3.50 times differences in shoot and root Cd concentrations, respectively. Principal component and cluster analyses assigned the 20 genotypes into Cd tolerant (5 genotypes) and sensitive (15 genotypes) groups.

CONCLUSIONS: Maize genotypes varied significantly in response to moderate Cd stress. Cadmium-tolerate genotypes optimized root morphology and Cd accumulation and distribution. This study could assist in the selection and breeding new cultivars with improved adaptation to Cd-contaminated soil for food and feed or land remediation purposes.