Evaluation of Biochemical Response and Defense Mechanism of Wheat Antioxidant Enzymes to Salinity Stress

  Understanding the reaction form and biochemical response of wheat cultivars about the salinity stress can help to better understand the defense mechanisms and identify the indicators and biomarkers of tolerance screening for salinity stress in this strategic plant and other field crop. For this purpose, biochemical traits related to salinity tolerance of wheat cultivars were evaluated as a factorial experiment based on a completely randomized design with tree replications. Experimental factors included wheat cultivars (Sarc 6 as tolerant cultivar and Chinese spring as susceptible cultivar) and sampling time series (control, 6, 12, 24, 48, 72 and 96 hours) after salinity stress. Salinity stress with a concentration of 250 mM of sodium chloride was applied to uniform 10-day seedlings in the two-leaf stage and sampling of shoot and root was performed. The studied traits included the ratio of potassium to sodium (K+/Na+), malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), and polyphenol oxidase (PPO). The results of analysis of variance showed that the effects of the cultivar (excluding peroxidase), the effects of time and the interaction of cultivar and time in all the studied traits, were significant. In one hand, the interaction results of cultivar and time indicated that the trend of changes in the studies traits were different, depending on the type of cultivar, the studied plant part and the sampling time. On the other hand, they also specified that the salinity stress was generally reduced the K+/Na+, increased the MDA and surged the activity of antioxidant defense enzymes in shoot and root of the studied cultivars as compared to control conditions (zero time). The results of group comparisons not only confirmed the efficiency and dominance of the Sarc 6 tolerant cultivar antioxidant defense system against the sensitive cultivar of Chinese springs, but it also emphasized the benefits of K+/Na+, SOD, and CAT biomarkers for wheat screening.