Cadmium sensitivity of main rice varieties cultivated in Guangdong Province under hydroponic condition

Objective This study aimed to establish a rapid screening method to facilitate the selection of suitable rice varieties for cultivated soils with different cadmium (Cd) contamination levels.

Methods A hydroponic experiment with graded Cd²⁺ concentrations (0, 0.01, 0.10, and 1.00 mg·L⁻¹) was conducted to investigate the absorption and translocation characteristics of Cd at the late tillering stages of 20 major rice varieties cultivated in Guangdong Province. The sensitivity of rice Cd accumulation was systematically analyzed.

Result Two-way analysis of variance revealed the significant difference in Cd accumulation capacity among cultivars under the three Cd²⁺ stress (P<0.05), with a significant interaction between cultivar and Cd²⁺ concentration. These variations were primarily attributed to genotypic differences in root uptake and stem-to-leaf translocation efficiency. Based on these findings, a rapid screening system for the hydroponic rice at tillering stage was established with the following criteria: ① Under hydroponic treatment with ρ (Cd²⁺)=0.01 mg·L⁻¹, twenty rice varieties were classified into low- and high-accumulation varieties by Cd content in rice root (threshold 45 mg·kg⁻¹) ; ② When ρ (Cd²⁺) increasing from 0.01 mg·L⁻¹ to 0.10 mg·L⁻¹, the sensitivity of rice to Cd²⁺ concentration can be determined by the increase multiple of Cd content in rice root (10-fold the threshold); ③ When ρ (Cd²⁺)=1.00 mg·L⁻¹, the transfer sensitivity of Cd can be evaluated by the stem and leaf to root translocation factor (TF, threshold 0.07). Using this rapid screening method, a preliminary screening of rice cultivars at the hydroponic tillering stage led to the identification of four Cd-accumulation sensitivity types: low-accumulation sensitive, low-accumulation insensitive, high-accumulation sensitive, and high-accumulation insensitive.

Conclusion Four categories of rice cultivars exhibiting differential Cd accumulation are identified as potential candidates for low-Cd rice cultivation. Field validation will be required to confirm the environmental stability of selected cultivars, and the evaluation system should be optimized to enhance its applicability and accuracy.