Salt Stress Triggers Distinct Cations Mobilization Strategies in Olive Tree (Olea Europaea L.): A Case Study Featuring Five Newly Selected Cultivars

Soil salinity affects 7% of the Earth’s land surface representing a threat for olive orchards, particularly in the Mediterranean region where the highest amount of worldwide olive oil production is established. This study aimed to investigate the physiological and nutritional responses of five newly developed olive tree cultivars under salinity stress, in an effort to identify potentially suitable varieties for olive tree cultivation in saline soils. Five Olea europaea (L.) cultivars (‘Tosca’, ‘Apollo’, ‘Minerva’, ‘Zeus’, and ‘Diana’) were subjected to a 90-day salt treatment through fertigation with a solution containing 60 mM NaCl, compared to a control irrigated with 0 mM NaCl. The study evaluated biomass parameters, macroelement balances and physiological traits, including net photosynthetic rate, to determine the impact of salinity. Salt treatment reduced biomass accumulation across all cultivars. However, the cultivar ‘Apollo’ displayed a notable resilience. Despite increased Na concentration in shoot and root tissues, ‘Apollo’ maintained nutrient homeostasis, unlike other cultivars that suffered macroelement imbalances under salinity. Additionally, ‘Apollo’ recorded a higher net photosynthetic rate compared to the other varieties, indicating an efficient physiological adaptation. The findings suggest ‘Apollo’ as a promising cultivar for saline environments. Its superior ability to balance nutrient uptake and sustain photosynthesis under salt stress highlights its potential for addressing the challenges of soil salinisation in the context of climate change.