Changes of Antioxidative Enzymes in Salinity Tolerance among Different Wheat Cultivars

The response of three wheat (Triticum aestivum L.) cultivars Banysoif 1 (C1), Sakha 68 (C2) and Seds 1 (C3) to salinity stress (-1.11 MPa NaCl) at germination and early seedling growth was investigated. According to the germination, dry weight production and tissue water content, C1 seemed to be more or less unaffected by salinity, whereas C3 was severely reduced and C2 was almost intermediated. Consequently, carbohydrate, protein and free amino acids contents were increased in C1 and C2, while the opposite occurred in C3 (except soluble proteins and free amino acids). On the other hand, while proline content decreased in C2 and C3, it markedly increased in C1 as a result of salinity stress. Na+/K+ ratio was higher in C3 than in C1. C2 was intermediate. Significant increase in SOD activity was observed in seedlings of C1 and C2. On the other hand, SOD activity was markedly decreased in C3 cultivar. Seedling extracts exhibited three SOD activity bands (SOD1, SOD2 and SOD3) in C1 and C2. While in C3 seedling, only two SOD activity bands (SOD1 and SOD3) were identified, whereas the SOD2 isozyme was not expressed under control or NaCl conditions in this cultivar. Salinity stress significantly increased POD activity in C1 and C3, but it markedly decreased the activity of POD in C2. Two isozymes of POD (POD1 and POD2) were observed in all groups of C1. The intensity and density of POD1 and POD2 markedly increased under salinity stress versus control group. In C2, salinity stress resulted in disappearance of POD1 as compared with control group. In C3, salinity stress induced the appearance of POD1 which disappear under control group. CAT activity in C1 and C2 was markedly increased under NaCl salinity. On the other hand, CAT activity was markedly decreased in C3. NaCl salinity did not affect APX activity in three wheat cultivars. In addition, lipid peroxidation level of salt-sensitive C3 markedly increased, indicating more damage to membrane lipids due to -1.11 MPa NaCl. Lipid peroxidation did not change in the salt-tolerant C1 at the same concentration of NaCl. C2 was intermediate. These results suggest that at seedling stage, C1 is appeared to be more tolerant than C2 and C3 under salinity stress.