Differential responses of two tomato cultivars to cadmium stress

【Objectives】To investigate the different responses of Cd accumulation in tomato cultivars exposed to Cadmium stress, a hydroponics experiment at seedling stage was performed using two tomato varieties, YSL189 with high Cd accumulation and HZ903 with low Cd accumulation, which were confirmed by our previous research. 【Methods】The experiment was performed in growth chamber, and morphological index, antioxidant enzyme activity, differences in Cd accumulation, ionic absorption rate and related gene expression in varieties were analyzed using seedling exposed to Cd 50 and 100 μmol/L. 【Results】 When exposed to 50 and 100 μmol/L of Cd, the root length of plants was more sensitive to Cd stress than plant height and biomass. Cultivar YSL189 exhibited higher tolerance in biomass and plant height, but lower root length than HZ903. Under both 50 and 100 μmol/L Cd treatments, the accumulation of Cd was reduced significantly in the order of roots, stem and leaves accordingly, and the Cd concentration in roots, stem and leaves of YSL189 was significantly higher than in those of HZ903. When the concentration of Cd in culture medium was over 20 μmol/L, the uptake rate of Cd in the roots of YSL189 was significantly higher than that in the roots of HZ903. The results of Real-Time PCR proved that the expression levels of transporter genes Nramp2, Nramp3 and ZIP in the roots of YSL 189 were higher than those in the roots of HZ903, and higher activities of SOD(superoxide dismutase), POD(peroxidase) and CAT(atalase) in roots and stems, SOD and POD in leaves were higher in YSL189 than those in HZ903, but no significant difference in concentration of TBARS(thiobarbituric acid reactive substance) between cultivars was found, indicating the degree of lipid peroxidation. 【Conclusion】 The higher Cd accumulation in YSL189 may be partly attributed to the higher Cd uptake rate, expression levels of Nramp2, Nramp3, and ZIP in roots of YSL189 were higher than those of HZ903; and the higher activities of antioxidant enzymes in YSL189 were induced by higher Cd concentration, indicating the stronger power to detoxify reactive oxygen species for YSL189 than HZ903.