Genotypic variation in growth and lead accumulation among Brassica juncea accessions.

Selecting (inter-varietal) Brassica juncea for tolerance to metal-contamination has been proposed as a strategy to develop superior genotypes for phytoextraction of lead (Pb) through selection and breeding techniques. To understand the differences among accessions of a single species to Pb accumulation, a pot experiment was conducted with three B. juncea accessions under levels of Pb added to the soil (0, 90, 180, and 540 mg kg-1). The duration of the growth period was 100 d. Pb concentration levels did not affect the flowering of B. juncea accessions. Plant height, shoot dry matter, and root dry matter were reduced linearly when soil Pb concentration increased to 540 mg kg-1. A significant interaction between Pb concentration levels and accessions was observed for Pb concentration in shoots and roots, indicating genotypic variation in Pb absorption. The concentration of Pb in shoots in accession PI 180266 was 51% higher compared to accessions PI 649105 and PI 432379 when soil Pb concentration increased to 540 mg kg-1. It can be concluded that the B. juncea accessions differed significantly in Pb uptake, and the selection of tolerant cultivars might be helpful for Pb phytoremediation of contaminated soils.

Growth and accumulation of Pb by roots and shoots of Brassica juncea L.

In this study, different soil Pb concentrations [24 (control), 80, 136, 362, and 1150 mg kg-1] were used to analyze the tolerance threshold and accumulation potential of Brassica juncea L. in a pot experiment under greenhouse conditions. In addition to growth and Pb accumulation, the following contamination indices were calculated: transfer coefficient (TC), translocation factor (TF), and tolerance index (TI). Growth and Pb accumulation were determined at 60 days after emergence. The Pb concentrations were determined using the flame atomic absorption spectrometry (FAAS). The plant height was affected by soil Pb contamination, and it decreased from 1.37 to 0.83 m when the soil Pb concentration increased from 24 (control) to 1150 mg kg-1, respectively. The Pb concentration in the shoots and roots increased as the Pb concentration in the soil increased, reaching 94 mg kg-1 in shoots and 783 mg kg-1 in roots when was grown under 1150 mg kg-1 of Pb. TF was <1 at all levels of contamination. The TI values suggested that B. juncea presented Pb tolerance in Pb contaminated soils. Our findings indicate that B. juncea has the potential to accumulate Pb in soil under tropical conditions.