Evaluation of Promising Pistachio Genotypes "Jookar1"‏‎ and "Jookar2" ‎for Drought Tolerance in Comparison with Common Native Iranian Rootstocks

Pistachio (Pistacia vera L.) is one of the most important agricultural products and export ‎items in Iran, which alone accounts for about one third of non-oil revenues in the agricultural ‎sector. Although pistachio is known as a plant adapted to environmental stresses, drought and ‎salinity are the most important factors in reducing production and one of the main problems ‎to achieve the real potential of this crop in Iran. The subject of the present project was to ‎evaluate the drought tolerance of two new genotypes ‎‎"Jookar1" and "Jookar2" as compared to two common native rootstocks "Badami Zarand" and ‎‎"Qazvini", which have tolerance to drought stress. In this regard, genotypes Jookar1 and ‎Jookar2 along with Badami Zarand and Qazvini were conducted in a factorial completely ‎randomized design (CRD) with five replications and five observations in each replication ‎in two ‎consecutive years (2018 and 2019). Evaluation of drought tolerance of rootstocks was done ‎at ‎three levels of normal (5-day irrigation cycle), mild stress (10-day irrigation cycle) and ‎severe stress (15-day irrigation cycle) using by morpho-physiological traits ‎related to water ‎stress. The results of irrigation treatments in the first and second year of the experiment ‎showed that there were significant differences between different levels of drought in all ‎morpho-physiological traits with the exception of stem water percentage and the number of ‎main root branches. Analysis of traits related to vegetative growth and physiological traits ‎related to plant water status showed that Jookar2 in mild stress and Badami Zarand and ‎Jookar1 in optimal and severe stress were selected as superior rootstocks. Although Jookar2 ‎showed significant sensitivity to drought in the early stages of growth in the first year of the ‎experiment and both vegetative growth and leaf area decreased significantly, this sensitivity ‎decreased in the second year of the experiment. Evaluation of morphological characteristics ‎of roots, crown and stem also confirmed the superiority of Jookar2 in mild drought stress ‎condition. However, no significant differences were observed between the four rootstocks ‎under normal and severe stress conditions. The clustering of the rootstocks based on all the ‎evaluated traits showed that in all three irrigation conditions, Badami Zarand and Jookar1 ‎were located in the same subgroup, which indicated the close genetic proximity of these two ‎rootstocks. Evaluation of three indices of uniformity, stability and viability in ‎greenhouse and orchard conditions screened Badami Zarand, Jookar1 and Qazvini as suitable ‎rootstocks. There was no damaged seedling in the orchard condition. The ‎findings showed that Jookar1 can be identified as a tolerant rootstock compared to Badami ‎Zarand and Qazvini which are considered as the best rootstocks in Iran and drought tolerance ‎of them has been confirmed in several researches. Jookar1 showed acceptable drought ‎tolerance and higher vegetative growth. Jookar2 was also significantly superior to the other ‎rootstocks in the mild drought stress, but its uniformity and viability were lower than the ‎other rootstocks after germination. In this study, Badami Zarand and Jookar1 were selected as ‎the best rootstocks that had desirable vegetative growth, drought tolerance, uniformity, ‎stability and viability.