Selection of cultivars to reduce the concentration of cadmium and thalliumin food and fodder plants

Pot and field experiments were carried out from 1994 to 1997 to investigate Cd and Tl uptake by various genotypes of maize, spring rape and kale on so ils contaminated with i) Cd by the addition of river sediments (aqua regia- extractable Cd: 24 mg kg(-1) soil) and ii) with Tl by deposits from a cemen t plant (HNO3-extractable Tl: 1.4 mg kg(-1) soil). In field experiments on the Cd-contaminated soil, Cd concentrations in shoo ts and kernels of fifty maize inbred lines differed by a factor of about tw enty (from < 1 to 15 mg Cd kg(-1) DM in shoots and from 0.02 to 0.5 mg Cd k g(-1) DM in kernels). After crossing inbred lines having high and low Cd co ncentration, Cd concentration of the resulting hybrids decreased, mainly as a result of a higher dry matter production (a dilution effect). In pot and field experiments on the Tl-contaminated soil, the selected cultivars of s pring rape showed only small differences in TI uptake, whereas Tl concentra tion in shoots of the kale cultivars differed more than twenty-fold tin the pot experiment from < 1 to 24 mg Tl kg(-1) DM and in the field experiment from 0.5 to 11.7 mg TI kg(-1) shoot DM). Two groups of cultivars with low a nd high TI concentrations could be distinguished. A nutrient solution experiment with radioactively labeled Tl showed that hi gher Tl concentration of kale in comparison to white cabbage can be attribu ted mainly to a higher uptake rate in kale (about 30-fold) with subsequent root-to-shoot translocation. The results show that, depending on plant species, selection and growing of cultivars with low heavy metal uptake on contaminated soils can substantia lly contribute to reduce the concentration of Cd and Tl in food and fodder plants.