Accumulation of Cadmium and Lead in Four Cultivars of Radish (Raphanus sativus L.) during the Seedling Period

Cadmium (Cd) and lead (Pb) are toxic even in small quantities and decrease crop yields. They are easily absorbed by plant roots, and thus enter the food chain, risking human health. Radish (Raphanus sativus L.) is a widely consumed root vegetable in Korea. Therefore, it is important to screen for a radish cultivar that exhibits low Cd and Pb accumulation and elucidate the Cd and Pb tolerance mechanism. In this study, we determined the effect of Cd and Pb stress on germination and growth in four radish cultivars, ‘Gaulgeojang’ (AG), ‘Iseogaul’ (IG), ‘Chongryong’(CR), and ‘Supertogwang’ (ST). Furthermore, Cd and Pb concentrations, production of nonprotein thiols (NPTs), and hydrogen peroxide (H2O2) levels were investigated in four cultivars of radish seedlings under Cd and Pb treatments. The cultivars showed tolerance to Cd and Pb stress during germination and seedling growth in the following order: CR > ST > IG > AG. CR, a tolerant cultivar, accumulated less Cd in roots and less Pb in both roots and shoots than the other cultivars. In contrast, AG, a sensitive cultivar, exhibited greater Cd and Pb accumulation in roots than the other cultivars. Cd and Pb treatments significantly increased the NPTs in all four cultivars; the highest level was found in CR. Cd and Pb treatments also increased H2O2 levels in all cultivars; the highest and lowest levels were observed in AG and CR, respectively. These results indicate that the greater Cd and Pb tolerance of CR may be attributable to its higher potential to limit Cd and Pb accumulation and to form complexes of metal-binding ligands with Cd and Pb. The results of this study provide information for the selection of the safest of the four common radish cultivars for growth in Cdand Pb-contaminated soils. Additional key words: contaminated soil, heavy metal accumulation, hydrogen peroxide, nonprotein thiols, sensitive cultivar, tolerant cultivar