Identification of low-Cd cultivars of sweet potato (Ipomoea batatas (L.) Lam.) after growing on Cd-contaminated soil: uptake and partitioning to the edible roots.

Cadmium (Cd) contamination in agricultural products presents a threat to humans when consumed. Sweet potato is the world's seventh most important food crop. The aims of this study were to screen for low-Cd sweet potato cultivars and clarify the mechanisms of low-Cd accumulation in edible roots. A pot experiment was conducted to investigate the variation of Cd uptake and translocation among 30 sweet potato cultivars grown in contaminated soils with three different Cd concentrations. Cadmium concentrations in edible roots were significantly different among cultivars and were significantly affected by Cd treatment, and the interaction between cultivar and Cd treatment. High-Cd cultivars have higher ratios of edible root/shoot Cd concentration and edible root/feeder root Cd concentration than low-Cd cultivars; however, the ratio of shoot/feeder root Cd concentration seems unrelated to the ability of Cd accumulation in edible roots. Four sweet potato cultivars, Nan88 (No. 10), Xiang20 (No. 12), Ji78-066 (No. 15), and Ji73-427 (No. 16), were identified as low-Cd cultivars. Cadmium translocation from feeder roots to edible roots via the xylem, and from shoots to edible roots via the phloem, controls Cd accumulation in edible roots of sweet potato cultivars.