Screening Alfalfa for Salt Tolerance Based on Lipid Peroxidation and Antioxidant Enzymes

In an effort to assess salt tolerance of alfalfa (Medicago saliva L.), herbage yield, lea fascorbate peroxidase (APX), catalase (CAT), and peroxidase (PDX) activities and malondialdehyde (MDA) content were measured in nine alfalfa cultivars grown in the field. Plants were grown under 20 (control), 60, and 120 mM NaCl salinity in Isfahan, Iran during 2010 to 2013. Based on correlation coefficients among the measured traits under salt-stress levels, MDA content had the highest correlation with herbage yield followed by CAT and PDX activities, respectively. Based on the reduction in herbage yield, under 120 mM NaCl stress, Isfahani and Rehnani; were the most salt tolerant, while Bami, Pioneer, and Nikshahri were the most sensitive cultivars. According to the relation between the salt tolerance and the measured traits, MDA content (r = 0.93) was the most important marker for salt tolerance followed by CAT (r = 0.58) and PDX (r = 0.53) activities, respectively. However, the relationship between salt tolerance and antioxidant enzymes activities was not as strong as that for MDA, and MDA content was well correlated with salt tolerance. Given the simplicity of MDA content measurement and the complexity of extractions and assays of the enzymes, CAT, APX, and PDX activities may not be used as markers, whereas, MDA content would be a much better indicator for assessing salt-tolerant cultivars in alfalfa.