Physiological Responses of Some Rootstocks and Interspecific Hybrids of Pistachio to Cold Stress under Greenhouse Conditions

Cold is an environmental factor limiting the growth and yield of agricultural crops. To find cold-tolerant pistachio rootstocks, a factorial experiment was conducted at Pistachio Research Center (PRC), Rafsanjan, Iran during 2017-2018. The factors included six rootstocks (Badami Zarand, Ghazvini, Sarakhs, Integerrima × Badami Zarand, Integerrima × Ghazvini and Integerrima × Sarakhs) and four thermal treatments (4, 0, -2, and -4°C) with three iterations. Seedlings in 6-8 leaf stage were placed in thermal treatments for two hours. Ionic leakage, pH of leaked solution, chlorophyll fluorescence, photosynthesis efficiency index, chlorophyll (a, b, total) and carotenoid contents were the traits assessed in this study. Based on the results, a decrease in temperature made an increase in ionic leakage rate, conversely making decreases in pH of the leaked solution, photosynthetic pigments contents, Fv/Fm and PI index. In addition, the highest photosynthetic pigments, pH of leaked solution, Fv/Fm and PI index were observed in Ghazvini and Integerrima × Ghazvini rootstocks. Meanwhile, the highest ionic leakage was observed in Integerrima × Badami Zarand. In aggregate, Ghazvini and Integerrima × Ghazvini were identified as the most cold-tolerant rootstocks, while Integerrima × Badami Zarand was the most cold-sensitive rootstock.