Assessment of changes in physiological and biochemical traits in four pistachio rootstocks under drought, salinity and drought + salinity stresses.

In this study, 7-month-old UCB-1, Badami, Ghazvini and Kale-Ghouchi pistachio rootstocks were exposed to control, drought, salinity and drought + salinity environments for sixty days. Total chlorophyll and total carotenoid contents decreased in all cultivars under drought, salinity and drought + salinity stresses. Under drought and salinity stresses, alone or in combination, Na⁺ and Cl^- ions increased in all four pistachio rootstocks, while K⁺ ion decreased only in Ghazvini and Kaleh-Ghouchi cultivars. Activities of ascorbate peroxidase, polyphenol oxidase, catalase and guaiacol peroxidase enzymes increased with induction of all three stresses in all cultivars except activity of ascorbate peroxidase in Kale-Ghouchi cultivar under induction of drought stress. Oxidative stress parameters including electrolyte leakage, malondialdehyde, other aldehydes and hydrogen peroxide increased under all three stress conditions in all genotypes. Contents of proline, total free amino acids and total soluble carbohydrates enhanced under drought, salinity and drought + salinity stresses, whereas the content of protein decreased in all pistachio rootstocks. In all evaluated traits except for the K⁺ ion content and APX activity, the highest impacts belonged to the drought + salinity > salinity > drought stresses, respectively. For the first time, we have proven that K⁺ ion content has a positive correlation with the ascorbate peroxidase, polyphenol oxidase, catalase and guaiacol peroxidase enzymes activities under drought + salinity stress. Finally, based on the bi-plot and cluster analyses, we have selected the UCB-1 > Badami > Ghazvini > Kale-Ghouchi cultivars as the most tolerant pistachio rootstocks under drought + salinity stress, respectively. This article is protected by copyright. All rights reserved.