Unravelling salt stress responses in two pistachio (Pistacia vera L.) genotypes

Pistachio tree (Pistacia vera L.) is among the tree species that are most tolerant to salinity stress. In the present investigation, we analyzed the behavior of two pistachio genotypes (Badami-e-Zarand (BZ) and Badami-e-Sefid (BS)) under different NaCl concentrations to reveal the mechanisms involved in salinity tolerance. A greater decline in several growth-related traits and biomass as well as relative water content was observed in BS seedlings than in BZ seedlings. Proline content, which is an indicator of stress, increased in both genotypes. Salinity induced oxidative stress in both genotypes, but the levels were higher for the BS genotype. The negative impact of salinity on photosynthetic process in BS was represented by a remarkable decrease in total chlorophyll and carotenoids, while the better performance of the BZ genotype under high salinity was accompanied by an increase in the activities of ascorbate peroxidase, catalase and guaiacol peroxidase. A significant increase in the superoxide dismutase activity in the leaves of BZ was observed under moderate salinity treatment. In both genotypes, Na+ content in leaf and root tissues increased progressively after salinity treatment. However, the leaves of BZ contained less Na+ and retained a lower Na+/K+ ratio. Moreover, under salinity treatment, BZ seedlings had a greater amount of NHX1 transcripts, which suggests that excess Na+ may be sequestered into root vacuoles to avoid deleterious effects of these toxic ions.