Characterization of Cd translocation and accumulation in 19 maize cultivars grown on Cd-contaminated soil: implication of maize cultivar selection for minimal risk to human health and for phytoremediation

Maize (Zea mays) has low Cd accumulation in grains and a high biomass compared to other crops. The capacities for Cd accumulation in different maize cultivars are, however, not fully understood. To reduce human health risk from maize grown in Cd-contaminated soil and to provide promising maize cultivars for the phytoremediation of Cd-polluted soil, a field experiment was conducted to screen low-Cd- and high-Cd-accumulation maize cultivars by evaluating the yield, Cd uptake, translocation, and accumulation differences among 19 maize cultivars. There were differences in straw dry weight (DW), root DW, and yield among the 19 cultivars. The cultivars Yudan19, Zhengda999, and Xianyu508 had a higher production compared to that of the other cultivars. The Cd concentrations in the roots were much higher than those in the straws and grains in all cultivars. The Cd accumulation factors (AFS) decreased in the order of accumulation factors in root (AFᵣₛ) > accumulation factors in straw (AFₛₛ) > accumulation factors in grain (AFgₛ). The Cd translocation factors (TFs) from root to straw (TFᵣₛ) were significantly (p < 0.05) larger than those from straw to grain (TFₛg) among all of the cultivars. The TFₛ for all of the cultivars was less than 1, and the lowest TFₛg (0.23) was found in cultivar Xiangyongdan3. The correlation analysis indicated that Cd concentrations in straws showed a significant (p < 0.01) as well as positive correlation with TFᵣₛ while a negative correlation with TFₛg (p < 0.01). Moreover, Cd accumulation in different tissues decreased in the order straw > grain > root. Among the 19 maize cultivars, Jixiang2118 and Kangnong18 accumulated the highest Cd amount in the aboveground tissues, and the corresponding values were 7,206.51 and 6,598.68 mg hm⁻², respectively. A hierarchical cluster analysis based on the Cd concentrations in grains and straws classified the 19 maize cultivars into four and two groups for a 0.4 minimum distance between clusters, respectively. Yudan19, Zhengda999, and Xianyu508 can be classified into one group in which low Cd in grains meeting the Cd tolerance limit in foods set by China National Standard, suggesting that those cultivars are safety for food and human health. However, Jixiang2118 and Kangnong18 can be classified as another group with potential application for phytoremediation in slightly or moderately Cd-polluted soil because of the high Cd accumulation in the aboveground tissues.