The Effect of Low Temperatures on Domestic and Wild Pistachio Rootstocks and Interspecific Hybrids Based on Physio-biochemical Indices

In recent decades, spring frost considered a serious threat in pistachio production (Pistacia vera). Considering that, Iran is one of the most important centers of pistachio production and has the highest variety of pistachios in the world, the identification of domestic and wild different rootstocks and their crosses to reach cold-tolerant rootstocks could be one of the effective solutions to face the challenge of spring frost. In this study, cold tolerance was assessed in fourteen rootstocks of pistachio domestic species (Badami Zarand, Sarakhs and Qazvini), interspecific hybrids (Qazvini×Khinjuk, Qazvini×Mutica, Qazvini × Baneh Baghi, Qazvini × Atlantica, Qazvini× Integerrima), non-domesticated species (Atlantica (P. atlantica), Integerrima, Khinjuk, Sarakhs, Mutica (P. atlantica sub. mutica) and Baneh Baghi (P. mutica × P. vera)) and UCB1 hybrid rootstock at low temperatures (4, 0 and -4 °C) for 2 hours. This experiment was conducted in a factorial completely randomized design with three replications on one-year-old seedlings in greenhouse conditions. The results showed that the rate of ion leakage, malondialdehyde and injury index percentage was significant (p <0.01) and their values were decreased in the cold-tolerant rootstocks than the cold-sensitive rootstocks. The interaction between treatments showed that the temperature of - 4 °C caused a significant reduction in ion leakage and malondialdehyde in the cold-tolerant rootstocks. Proline was increased in the cold-tolerant rootstocks compare to cold-sensitive rootstocks. The results of cation leakage percentage were significant in temperature and rootstocks (p <0.01). The results showed that the highest percentage of cation leakage related to potassium and there was a positive and significant correlation between calcium and magnesium and cell membrane stability. According to the results, the most sensitive rootstock was UCB1, Integerrima, Khinjuk and Baneh Baghi, respectively. Hybrids Qazvini , Baneh Baghi, Khinjuk and Integerrima rootstocks were significantly reduced under low-temperature stress. Mutica, Qazvini×Mutica, Sarakhs, Qazvini, Qazvini×Atlantica rootstocks, improved physiological and biochemical traits and maintained cell membrane integrity and finally showed greater tolerance to frost and freezing temperatures, which can be considered in the breeding program.