Antioxidative Response of Strawberry (Fragaria ananassa Duch.) Cultivars and Wild Species (Fragaria viridis L.) to NaCl Induced Oxidative Stress

Two experiments were conducted during November 2007-April 2008 and November 2008-April 2009 to investigate the effect of NaCl on strawberry cultivars ('Selva' and 'Chandler') and a wild species (Fragaria viridis L.). The change in lipid peroxidation and the possible involvement of the antioxidant system in relation to NaCl stress was investigated. The plants were grown in pots and regularly watered with half strength Hoagland nutrient media. At four leaves stage the plants were treated with 0.0, 0.25, 0.50, 0.75, 1.0 or 1.5% NaCl for 25 days with five days interval. The investigations were carried out in leaves at different stages of the crop such as pre-flowering, flowering and fruiting. In Fragaria viridis L., the constitutive level of lipid peroxidation was lower, but the activities of super oxide dismutase (SOD), ascorbate peroxides (APOX), catalase (CAT) and proline (PRO) were inherently higher than those of Fragaria x ananassa Duch. cultivars. Compared to Fragaria x ananassa Duch. lipid peroxidation was also lower and the activities of SOD, APOX, CAT and PRO were higher in Fragaria vesca/viridis at 0.50 and 0.75% NaCl. It was observed that there was a gradual increase in growth parameters and antioxidative enzyme activities in cultivated strawberry with increase in NaCl concentration from 0.25, 0.50 to 0.75%. Above 0.75% the inhibitory effect was noticed till 3.0% and thereby growth remained stunted even causing death of the plants. These results possibly suggest that the wild salt tolerant strawberry Fragaria viridis exhibit a better protection mechanism against oxidative damage by maintaining a higher inherited and induced activities of antioxidant enzymes than the relatively sensitive plants of cultivated strawberry (Fragaria x ananassa Duch.) cultivars.