Three (Turkish) olive cultivars display contrasting salt stress-coping mechanisms under high salinity

All olive cultivars survived high salinity, yet, the question was how they orchestrated antioxidative defense, mannitol accumulation and ion sequestration with different efficiencies due to their genetic makeup. A Mediterranean plant, Olea europaea (olive) is well adapted to high temperature, high light intensity and dry soil conditions hence accepted to be moderately salt tolerant. Control of Na+ and Cl− uptake, accumulation of osmoprotectants and high antioxidative capacity were all attributed to salt stress tolerance of olive, however, there is a great discrepancy between the efficiency and onset of these processes among different cultivars. In present study, three olive cultivars namely Ayvalik, Gemlik and Kilis which are well adapted to different climatic regions extending from cool and high precipitation receiving regions to long hot and dry periods with high light intensity through the growth season were tested for their relative salt-tolerance mechanisms. For this aim, 1-year-old cuttings of these cultivars were treated with 0, 100, 200 and 300 mM NaCl for 30 days. Several physiological and biochemical processes along with their growth performance were analyzed during the experimental period. In general, we found discrepancies in salt stress-coping strategies of these cultivars. Efficient osmoprotection in Gemlik cv. lead to a better leaf water status and photosynthetic performance while, active ion sequestration and high levels of SOD and POX enabled Kilis cv. to be protected from the negative impact of salinity. Moreover, Ayvalik cv. accumulated high levels of mannitol that probably served as an antioxidative molecule to cope with salt stress.