In vitro breeding of Brassica juncea L. to enhance metal accumulation and extraction properties.

In vitro breeding and somaclonal variation were used as tools to improve the potential of Indian mustard (Brassica juncea L.) to extract and accumulate toxic metals. Calli from B. juncea were cultivated on a modified MS medium supplemented with 10-200 microM Cd or Pb. Afterwards, new B. juncea somaclones were regenerated from metal-tolerant callus cells. Three different phenotypes with improved tolerance of Cd, Zn and Pb were observed under hydroponic conditions: enhanced metal accumulation in both shoots and roots; limited metal translocation from roots to shoots; reduced accumulation in shoots and roots. Seven out of thirty individual variants showed a significantly higher metal extraction than the control plants. The improvement of metal shoot accumulation of the best regenerant (3 x Cd, 1.6 x Zn, 1.8 x Pb) and metal extraction (6.2 x Cd, 3.2 x Zn, 3.8 x Pb) indicated a successful breeding and selection of B. juncea, which could be used for phytoremediation purpose.