DIFFERENTIAL RESPONSES OF FOUR SOYBEAN (GLYCINE MAX L.) CULTIVARS TO SALINITY STRESS

Salinity stress-induced morphological, physiological and biochemical responses of four soybean cultivars (MAU-61, LSB-1, NRC-37 and MACS-57) were studied in 30 days old plants by treating them with 100 mM, 200 mM and 300 mM concentrations of NaCl respectively. The effect of salinity on plant growth was studied by measuring the growth of the plant, branch length, leaf area. The water relations of soybean cultivars under salinity were estimated by studying the relative water contents and water uptake capacity. The response of the soybean plants to salinity stress was analysed by estimating the levels of carbohydrates, total free amino acids, proline, glycine betaine along with the enzymatic activities of superoxide dismutase and sucrose phosphate synthase. Carbohydrates and SPS activity were decreased in the soybean plants under salinity stress whereas the contents of proline, glycine betaine and total free amino acids were increased along with superoxide dismutase activity. Native polyacrylamide gel electrophoresis showed the accumulation of two SOD isoenzymes Mn-SOD and Cu/Zn SOD under salinity stress. Differential expression of these enzymes showed that the expression of these enzymes under salinity stress was high in roots. This study reveals that the varieties NRC-37 and MACS-57 showed a better performance under salinity stress, when compared to that of MAU-61 and LSB-1 which was very well correlated with their biomass contents.