Isolation and partial characterization of a lead-accumulating Brassica juncea mutant

A new screening method for non-destructive, high-sensitivity, high-throughp ut isolation of plant mutants capable of accumulating large amounts of heav y metals has been developed. This method is based on incubating seedlings i n a solution containing radioisotopes of the metals of interest and visuali zing the tissue accumulation of these metals with a phosphorimager. We used this technique to isolate mutants of Brassica juncea (L.) Czern with incre ased accumulation of Cd and Pb for use in phytoremediation, an emerging tec hnology using plants to remediate polluted soil and water. Approximately 50 ,000 M2 seedlings were screened and 21 mutants were recovered that retained increased accumulation through the third generation. Mutant 7/15_1 is char acterized by enhanced Pb accumulation per unit of root fresh weight, stunte d root growth, and decreased root cell size. Data indicate that roots of 7/ 15-1 contain more cell-wall material on a fresh-weight basis than roots of the wild-type, which may at least partially explain its ability to accumula te more Pb.