Salt stress tolerance mechanisms in Olea europaea L. investigated by ionomic and metabolomic approaches

Olive tree is one of the most important agricultural crops in Mediterranean Basin where salinity is a current problem that could negatively affects its production. Despite olive tree is considered moderately tolerant to salinity negative effects depends on genotype, concentration, and time of exposure to NaCl. Tolerance mechanisms in olive tree are mainly related to the capacity of Na+ exclusion and translocation as well as changes in terms of ion and metabolites concentration and distribution. The aim of this PhD project was to identify salinity tolerance mechanisms in olive tree thought ionomic and metabolomic approaches considering also physiological responses. To achieve this aim, silicon priming was applied on two olive cultivars with opposite salt tolerance (‘Frantoio’ and ‘Leccino) exposed to 100 mM of NaCl (Annex I). Then, second experiment was performed with cultivar ‘Leccino’ that was also pretreated with a higher concentration of Si and then exposed to 120 mM of NaCl (Annex II). Third experiment consisted in an exploratory analysis of how NaCl combined with inorganic and organic contaminants influenced on physiological responses and assess the effects on fruit quality in cultivar ‘Cipressino’ (Annex III). As general conclusions, we confirmed that salinity tolerance is cultivar dependent, and Si pretreatment effects in olive tree under salinity exposure were not only cultivar dependent that also dose dependent. Regarding NaCl exposure combined with others organic and inorganic contaminants, ‘Cipressino’ cultivar mobilized Na+ to all organs of the plants specially to the fruits similar to others salt-sensitive cultivars; however, no other pollutants translocated into olive fruits indicating how olive production and oil quality should not be compromised.