Effect of salt stress on some physio-biochemical traits and antioxidative enzymes of two Brassica species under callus culture

The changes in lipid peroxidation, H2O2, proline, protein, involvement of different antioxidant systems (catalase, guaiacol peroxidase, ascorbate peroxidase) and callus-related traits were investigated under salt stress in the callus of two different ploidy levels of Brassica including B. juncea and B. oleracea. The calluses of B. juncea genotypes were less sensitive to NaCl stress in comparison with those of B. oleracea while increasing the concentrations of NaCl from 0 to 200 mM. Tetraploid genotype (B. juncea cr3356) showed a significant increase in the contents of protein and proline, and guaiacol peroxidase activity and catalase enzymes at higher salinity levels. In addition, a significant decrease occurred in the amount of H2O2 and malondialdehyde along with increasing the salinity intensity. Diploid cultivar (B. oleracea bra 2828) had the lowest enzymatic activities and the highest content of H2O2 and malondialdehyde along with an increase in the salinity level. Therefore, this genotype was identified as the most sensitive cultivar under the salinity stress. The salinity resistance difference between diploid and amphidiploid species could be attributed to the differences in the ploidy level of these species. This result underlines the fact that the tetraploid genome of B. oleracea could be considered as a suitable candidate for production under salinity conditions through maintaining higher activities of antioxidant enzymes.