The effect of salt stress on biochemical traits and relation with salt tolerant of alfalfa cultivars in field

Salt stress affects alfalfa growth especially at germination and seedling stages. Therefore, selection of salt tolerant cultivars and find possible mechanisms of salt tolerant are important at these stages. This experiment was conducted to evaluate nine alfalfa cultivars including Rehnani, Esfahani, Gharehyonje, Ranjer, Hamedani, Yazdi, Nikshahri, Pioneer and Bami for the salt tolerant and enzymes activities at germination and seedling stages in labratovar and field condition at four harvested time. Plants were subjected to four salt treatments including, 0, 60, 120 and 180 mM NaCl for 7 days In the Laboratoy, root and shoot lengths and weights and the activities of superoxide dismutase (SOD: EC 1.15.1.1), catalase (CAT: EC 1.11.1.6), peroxidase (POX: EC 1.11.1.7), ascorbate peroxidase (APX: EC 1.11.1.11) and glutathione reductase (GR: EC 1.6.4.2), and the rate of lipid peroxidation level in terms of malondialdehyde (MDA) were measured. In the field, high, Leaf area index (LAI), nodul number, yield forage and protein percentage were measured. Root and shoot length and weights decreased under salt treatments. However, there were differences between the cultivars and Rehnani, Esfahani were the most tolerant and Pioneer and Bami were the least tolerant cultivars. The activities of SOD, GR, POX and APX were higher in salt tolerant and lower in salt sensitive cultivars. The MDA content was lower in salt tolerance cultivars as compared to sensitive cultivars. These results showed that the SOD, GR, POX, APOX activities and MDA content may be used to select salt tolerance cultivars at the germination and seedling stages. The dry forage was higher in Rehnani cultivar in third harves whereas Bami cultivar was the lowest dry weight. Comparison between lab and field results showed that the good relation was among the activity antioxidant enzymes in seedling stage and salt tolerant in field stage.The results also suggest that SOD, GR, POX and APX may play an important role in salt tolerant mechanisms in alfalfa.