EFFECTS OF NaCl TREATMENTS ON SEED GERMINATION AND ANTIOXIDANT ACTIVITY OF CANOLA (BRASSICA NAPUS L.) CULTIVARS

Effects of salt stress on germination, seedling growth and activity of antioxidant enzymes in leaves of six cultivars of canola (Brassica napus L.) were investigated on two F1 hybrids (Hyola401, Hyola330) and four open pollinated cultivars (Zarfam, Okapi, RGs003 and Sarigol). Seeds were germinated under various levels of salinity (0, 50, 100, 150 and 200 mM NaCl solutions). An increase in NaCl concentrations progressively inhibited seed germination. Hyola401 showed the highest germination percentage at all salinity levels. Seedling growth parameters were affected by salt stress particularly at 150 and 200 mM. Leaf antioxidant activities of superoxide dismutase (SOD), ascorbate peroxidase (APX) and glutathione reductase (GR) were increased by salinity increase up to 150 mM while decreased at 200 mM NaCl concentration. Although constitutive levels of activity of antioxidative enzymes were almost the same among the canola cultivars, Hyola401 induced antioxidant enzyme activities were more efficient when subjected to NaCl treatment. Among the tested cultivars, F1 hybrid ‘Hyola401’ could be considered as salt tolerant as possessing higher germination percentage, better seedling growth and antioxidant activities under salinity stress. On the other hand, F1 hybrid ‘Hyola330’ performed inferior to said aspects and was the most susceptible cultivar to salinity stress. Introduction Oilseed rape, canola (Brassica napus L.) is considered as the second most important source of vegetable oil providing 13% of the world ́s supply (Raymer 2002). The world ́s commerce is largely supplied by two species, namely Brassica napus L. and Brassica rapa L. Seeds of these species commonly contain 40% or more oil and produce meal with 35 40% protein. Salinity is a major environmental stress affecting over 800 million hectares of land throughout the world which accounts for more than 6% of the world total land area (Munns and Tester 2008; Arzani 2008). Salinity, like other environmental stresses causes an increase of production of reactive oxygen species (ROS) (Rahimizadeh et al. 2007). Antioxidant defense systems have been developed in aerobic cells to counteract the deleterious effects of ROS (Ghassemi-Golezani et al. 2009). When plants are exposed to environmental stresses oxidative damage may result because the balance between the production of ROS and their detoxification by the antioxidative system is hampered ( Hernández et al. 1993). Superoxide dismutase (SOD) is the first line of defense against ROS (Alscher et al. 2002), that catalyzes the dismutation of superoxide to hydrogen peroxide (H2O2) and oxygen (O2). The generation of ROS and increased activity of many antioxidant enzymes during salt stress have been reported in crop plants (Sairam et al. 2002, Mittova et al. 2002, Vaidyanathan et al. 2003). In sesame, activity of SOD (CAT), GR and malondialdehyde (MDA) were increased under salt stress conditions (Koca et al. 2007). Dai et al. (2009) demonstrated that the content of SOD, CAT and POD in Brassica napus L. have been increased under stress conditions. Crop species or genotype possessing better germination and seedling growth under salt stress will be more stress *Corresponding author. .