The Effect of Salinity Stress on Fruit Morpho-Physiological Traits, Fatty Acid Profile and the FADs Genes Expression in Some Olive Cultivars

Salinity stress is one of the adverse environmental factors that affects fruit yield and the quantity and quality of olive oil. However, the extent of this effect can be different among different cultivars and genotypes of olives (Olea europaea L.). This experiment was carried out to evaluate the effects of salt stress on the vegetative, morphological, biochemical, and molecular traits of two olive cultivars (‘Zard’ and ‘Direh’) and a promising genotype (‘Dehsefid’). Olive trees were subjected to four levels of saline irrigation (control, 65, 130, and 195 mM NaCl). The results demonstrated that the ‘Dehsefid’ genotype exhibited the lowest reduction in growth parameters (current-year shoot growth, diameter, fruit fresh weight, diameter and length and pit fresh weight) and oil content across both experimental years and varying salinity levels. Fatty acids profile analysis revealed significant changes in fatty acid composition among the cultivars. While all cultivars experienced a decrease in oleic acid content and an increase in linolenic acid content with increasing stress intensity, these changes were more pronounced in ‘Dehsefid’ genotype. Expression analysis of key genes (OeFAD2, OeFAD6, and OeFAD7) revealed a correlation between their expression and fatty acid content. The significant up-regulation of OeFAD7 in ‘Dehsefid’ was directly linked to the increased linolenic acid content, while OeFAD2 induction was associated with increased linoleic acid content in all cultivars. These findings suggest that the ‘Dehsefid’ genotype is better adapted to salt stress and could be a promising candidate for further studies on salt tolerance in olives.