Selection and characterization of lead-tolerant sweetpotato cultivars for phytoremediation

Lead (Pb) is one of the most toxic heavy metals (HMs) for plants and the environment. Sweetpotato [Ipomoea batatas (L.) Lam], the sixth most important food crop in the world, is tolerant to various environmental stresses, owing to its high antioxidant capacity. In this study, we selected sweetpotato cultivars showing high tolerance to lead (Pb) for phytoremediation-related applications. Young seedlings of 20 sweetpotato cultivars were treated with 30 mM Pb. Daeyumi (KO-12) and Dahomi (KO-5) were selected as Pb-tolerant and -sensitive cultivars, respectively, based on their photosynthetic activity and growth inhibition index (I50). In the Pb treatment, hydrogen peroxide and malondialdehyde contents of KO-12 were 1.5-fold less than those of KO-5. In addition, KO-12 showed a higher ability to accumulate Pb in roots and leaves than KO-5. Expression levels of four Pb-responsive genes, including the metallothionein gene IbMT1, were higher in the roots and leaves of KO-12 than in those of KO-5. Interestingly, KO-12 showed greater tolerance to high Pb concentrations than sunflower and rapeseed, which have been well-studied for phytoremediation. Our results suggest that sweetpotato is a suitable biomaterial for the phytoremediation of soils contaminated with HMs, including lead, for sustainable agriculture.