Multiple linear regression and linear mixed models identify novel traits of salinity tolerance in Olea europaea L.

Olive can be considered as moderately tolerant to salinity, with marked differences among cultivars. In the present study, two olive cultivars with different salt tolerance, 'Leccino' (sensitive) and 'Frantoio' (tolerant), were treated with 120 mM of NaCl for 30 days. We measured the expression of genes involved in the management of sodium in the leaves, such as NHX, SOS1 and H+ ATPase, and the concentration of Na+, K+, Mn2+, Mg2+ and Ca2+ in the roots, bark, xylem and leaves of the olive plants. The results were analyzed with multiple linear models and mixed models. Furthermore, we utilized the analysis of covariance to find significant relationships in our data. Both cultivars significantly reduced net photosynthesis and increased water-use efficiency after 30 days of treatment. Sodium accumulated significantly in the roots of both cultivars, and 'Leccino' plants were also able to translocate it to the leaves and the bark. The NHX and vacuolar ATPase subunit E genes were significantly overexpressed in both the cultivars treated with NaCl. The SOS1, ATPase11 and ATPase8 genes were overexpressed in 'Frantoio'. The covariance between gene expression and element concentrations data was analyzed to identify significant interactions between cultivars and treatments. Na+ accumulation in the roots of 'Frantoio' was positively related to the accumulation of K+, Mn2+, Mg2+ and Ca2+ in the xylem, bark and leaves. 'Frantoio' capability to mobilize elements, especially Ca2+, together with the overexpression of key genes for sodium management, could be crucial for salt tolerance.

Cations and Phenolic Compounds Concentrations in Fruits of Fig Plants Exposed to Moderate Levels of Salinity.

Fig trees are often grown in areas affected by salinity problems. We investigated changes in the concentrations of 15 phenolic compounds and mineral elements (Mg, Ca, K, Zn, Cu, Mn, Mo, Fe, Na) in fruits of fig plants (Ficus carica L. cv. Dottato) subjected to irrigation with saline water (100 mM of NaCl) for 28 days. We used UHPLC-MS/MS techniques to determine chlorogenic acid, tiliroside, catechin, epicatechin (ECTC), p-coumaric acid, trans-ferulic acid, phloridzin, phloretine, quercetagetin 7-O-glucoside, rutin, quercetin 3-O-glucoside, kaempferol 3-O-rutinoside, kaempferol 7-O-glucoside, kaempferol 3-O-glucoside, and quercetin. There was a steep gradient of Na+ concentrations between the root and the canopy of salinized plants, but leaf Na+ was similar in control and salt-treated plants. Quercetin, ECTC, and chlorogenic acid were the most abundant phenolic compounds in fig fruits. Salinity increased total phenols by 5.6%, but this increase was significant only for ECTC. Salt stress significantly increased Zn and Mg concentration in the fruit. Leaf levels of K, Mg, Ca, and Mn were similar in control and salinized plants. Moderate salt stress appears to improve fig fruit quality because of its positive effect on nutrients and antioxidant compounds such as epicatechin.