Contents lists available at ScienceDirect Scientia Horticulturae journal homepage: www.elsevier.com/locate/scihorti Salicylic acid and calcium pretreatments alleviate the toxic effect of salinity in the Oueslati olive variety Kawther Methenni a, ⁎ , Mariem Ben Abdallah a , Issam Nouairi b , Abderrazek Smaoui c , wided Ben Ammar a , Mokhtar Zarrouk a , Nabil Ben Youssef a,d a Laboratory of Olive Biotechnology, University Tunis El Manar, Biotechnology Center of Borj-Cedria, P.O. Box 901, 2050 Hammam-Lif, Tunisia b Laboratory of Legumes, Biotechnology Center of Borj-Cedria, P.O. Box 901, 2050 Hammam-Lif, Tunisia c Laboratory Of Extremophyll Plant, Biotechnology Center of Borj-Cedria, P.O. Box 901, 2050 Hammam-Lif, Tunisia d Department of Biology, College of Science, Imam Abdulrahman Bin Faisal University, P.O. Box 1982, Dammam, 31441, Kingdom of Saudi Arabia ARTICLE INFO Keywords: Calcium Chloride Olive Pretreatment Salicylic acid ABSTRACT Pretreatment in arboriculture is a new physiological approach allowing the improvement of plant tolerance to salt stress. This research aims to screen various pretreatments of salicylic acid (SA) and/or calcium chloride (CaCl 2 ) to mitigate the effect of salinity on ‘Oueslati’ olive plants (Olea europeae L.) on physiological attributes under 200 mmol L -1 of NaCl application. One - year- old plants were transplanted to sand culture in a green- house, and were pretreated with two levels of foliar application of SA (0.5 and 1 mmol L -1 ) and by adding CaCl 2 (10 and 20 mmol L -1 ) to the culture solution twice a week for 45 days. At the end of the pretreatment, the plants were subjected to 200 mmol L -1 NaCl exposure for 75 days. The result showed that shoots and roots growth were decreased significantly due to salinity, sodium (Na + ) ions increased and K + /Na + ratio decreased in leaves. Rate of assimilation (A), transpiration (E) and stomatal conductance (g s ) decreased in leaves. Salinity caused significant increase in both malondialdehyde (MDA) and H 2 O 2 concentration, a decrease in total polyphenol and flavonoid levels and an increase in scavenging activity (IC50) (21%). Moreover, salinity caused a decrease in xylem and an increase in phloem thickness in leaves. However, pretreatments could partly improve the adverse effects of salinity on the most studied parameters. SA (1 mmol L -1 ) is able to restrict Na + ions transport from the roots to the leaves limiting its toxicity in the sensitive organs. SA (1 mmol L -1 ) and CaCl 2 (10 mmol L -1 ) pre- treatment alleviate the effects of salinity on dry weight of shoots and roots as well as, photosynthetic activity in pretreated plants. Moreover, at the same pretreatment, results showed a decrease of the Na + translocation to the leaves. Furthermore, it has been shown that pretreatment of ‘Oueslati’ olive plants enhance the non-enzymatic antioxidant activity (total polyphenol and flavonoid content).These results suggest that pretreatments may be useful methods to increase salt tolerance in olive, for use in arid and semi-arid environments. 1. Introduction Olive growing in Tunisia covers almost 1.7 million hectares with 82 million trees.The average density is about 40 feet per hectare and varies widely from the north (about 100 feet per ha) to the south (only 20 feet per hectare). ‘Oueslati’ is a native variety to the highlands. It was found in the northern part of central Tunisia and in particular in Oueslatia in the governorate of Kairouan. Olive tree is a major crop in wide arid and semi-arid areas due to its acclimation ability to water deficit and the demand for olive products, especially olive oil, which is considered as a key ingredient for a healthy diet (José-Enrique Fernandez, 2014) has been increased. Traditionally, the olive tree was grown in rainfed conditions. They have been extended to irrigated land in recent decades. In arid and semi-arid regions, the limited availability of water and the increase in urban water use reduce fresh water for irrigation. Thus, large quantities of saline water are used for irrigation of olive trees in arid regions (Ben Ahmed et al., 2012). The deleterious effects of salinity on plant growth are associated with low osmotic potential of the soil solution (water stress), nutritional imbalance, specific ion ef- fects (salt stress) or combination of these factors (Shannon, 1998). The maintenance of an appropriate plant water status under stressed con- ditions is essential for continued growth of the plant. This process can be achieved by stomatal regulation (Chartzoulakis, 2005; Tattini and Traversi, 2009) and accumulation of compatible solutes in either leaves or roots. Salt tolerance in olive cultivars is associated with effective mechanisms of ion exclusion and retention of Na + and Cl - in the root https://doi.org/10.1016/j.scienta.2018.01.060 Received 23 November 2017; Received in revised form 26 January 2018; Accepted 27 January 2018 ⁎ Corresponding author at: Laboratory of Olive Biotechnology, University Tunis El Manar, Center of Biotechnology of Borj-Cédria, P.O. Box 901, 2050 Hammam-Lif, Tunisia. E-mail address: kawthermethenni@gmail.com (K. Methenni). Scientia Horticulturae 233 (2018) 349–358 Available online 16 February 2018 0304-4238/ © 2018 Elsevier B.V. All rights reserved. T