Evaluation of the activity of antioxidant enzymes and the amount of hydrogen peroxide in obtained using hybrid seedlings rootstock from intraspecific and interspecific crosses (P. vera × P. integerrima) under drought stress

Iran has the world's agricultural industry is a valuable product pistachios (Pistacia vera L) and the products economically one of the most important horticultural crops in Iran. Various stresses particularly drought, pistachio cultivation has always faced a lot of difficulties and obstacles to the extent that in some provinces faced with significant challenges. Breeding processes including control crossings to increase resistance, can be safe and permanent solution for reducing the deleterious effects of drought stress on plants to be considered. Therefore, considering the importance of pistachio product in the country as a strategic product and as well as Iran's location in dry and semi-arid conditions, research in order to develop drought-tolerant hybrid is essential.

In this study, in order to investigate the effect of drought stress on the level of activity of some antioxidant enzymes and some growth characteristics pistachio seedlings and identification of tolerant rootstocks, this experiment was designed. The experiment was conducted as factorial based on a Completely Randomized Design with four replications in the research greenhouse of Gorgan University of Agricultural Sciences and Natural Resources during 2018-2019. The treatments were consisted of five pistachio rootstocks Ahmad Aghaei, Akbari, Sorkheh Hosseini, Garmeh, Fandoghi and five interspecific hybrids (Ahmad Aghaei × Integerrima, Akbari × Integerrima, Sorkheh Hosseini × Integerrima, Garmeh × Integerrima and Fandoghi × Integerrima) and three levels of drought including control (100 % field capacity), mild stress (65% of field capacity) and Severe stress (30% of field capacity) were applied on 3 months old the seedlings for 84 days.

According to the results, the effects of rootstock and drought and as well as their interaction on most of the studied traits were significant (P ≤0.01). However, no significant effect (P≥ 0.05) was observed on stem length in relation to rootstock and drought interaction. The results showed that with increasing levels of drought, the activity of catalase, peroxidase, ascorbate peroxidase, superoxide dismutase, guaiacol peroxidase, hydrogen peroxide in leaves and roots and also, the amount of leaf fall in the studied pistachio seedlings increased and the number of leaves, stem length and diameter decreased.increased in the studied seeds. The highest amount of enzyme activity was observed in severe drought treatment and the lowest amount was observed in control treatment. On the other hand, in relation to leaf number, length and stem diameter, the highest and lowest values were observed at the control level and severe stress, respectively. Based on the results, different physiological responses were observed between the seedlings in their response to water stress. Drought tolerant rootstocks Hydrogen peroxide content and lower leaf fall percentage and higher enzymatic and growth activity than drought-sensitive rootstocks. The highest Fandoghi rootstocks and the hybrid rootstocks of Sorkheh Hosseini × Integerrima, Ahmad Aghaei × Integerrima and Akbari × Integerrima showed the least increase in the amount of Hydrogen peroxide leaves and roots and leaf fall between the rootstocks. In connection with these traits the seedlings rootstocks of Ahmad Aghaei, Sorkheh Hosseini, Garmeh × Integerrima, Akbari, Garmeh and Fandoghi × Integerrima were ranked next in terms of drought tolerance, respectively.

Based on the results of the present study it seams roots stock of Sorkhe Hosseini × Integerrima, Ahmad Aghaei × Integerrima and Akbari × Integerrima could be as potential seedlings in deal with drought tolerant. These hybrids possibly owns as gene pool for breeding high-yielding cultivars in arid regions.