Investigation of interaction effects of water and salinity stress on pistachio seedlings (Badami rootstock) Abstract Drought and salinity stresses are among the important environmental and biological stresses that reduce agricultural and horticultural productions all over the world, especially in arid and semi-arid regions. Pistachio nut is one of the most important exporting products of Iran and its tree is well known to have a moderate to high tolerance to saline water and soil. Recently in Iran, the cultivation of pistachio is faced with serious problems such as water scarcity and salinity and rising saline soils and the yield per hectare has dropped dramatically. Due to the fact that native cultivars of plants in each region show better adaptation reactions in critical conditions, this experiment was performed to eva‎luate the tolerance of pistachio Badami rootstock as a native cultivar of Ardakan region to salinity and drought stresses. In this research, a factorial experiment was conducted in a completely randomized design with three replications in greenhouse of Pistachio Research Station of Ardakan city located in Yazd province. The drought treatments were applied as 5 (I1), 10 (I2) and 15 (I3) days of irrigation interval. Four salinity levels of irrigation water included S1: fresh water with salinity of 0.5 dS/m, S2: qanat water with salinity of 4 dS/m, S3: mixture of well water and qanat with salinity of 7 dS/m and S4: the well water with salinity of 10 dS/m. At the end of the treatments period, in addition to the actual evapotranspiration of each treatment, morphological traits of seedlings including shoot fresh and dry weights, seedling height, stem diameter, fresh and dry root weights, root diameter, main root length, root to shoot ratio and leaf area were measured. The results showed that the main effect of irrigation interval on all measured traits except seedling height and root to shoot ratio and the main effect of irrigation water salinity on all traits except root to shoot ratio were significant at 1% level, while the interaction effects of irrigation interval and salinity were significant on evapotranspiration, root diameter, fresh and dry root weights and leaf area. The increasing irrigation water salinity from 0.5 to 10 dS/m, the average evapotranspiration decreased by 17% and increasing the irrigation interval from 5 to 15 days, the average evapotranspiration decreased by 49%. Increasing the irrigation interval caused a greater decrease in evapotranspiration than increasing the irrigation water salinity. Comparison of shoot and root dry weights at the lowest salinity level compared to the highest salinity level showed a decrease of 60 and 58%, respectively. Increasing the irrigation interval from 5 to 15 days also reduced the average dry shoot and root weights by 27 and 29%, respectively. With increasing irrigation interval from 5 to 15 days and increasing salinity from 0.5 to 10 dS/m, stem diameter decreased significantly by 15 and 40%, respectively, while the corresponding values for reducing root diameter were 9 and 45%, respectively. With increasing irrigation interval from 5 to 15 days and increasing salinity from 0.5 to 10 dS/m, leaf area decreased by 46 and 79%, respectively. In general, based on the results, the effect of salinity on reducing the shoot and root morphological traits of pistachio was more than the effect of drought. The results also showed that the slope of the relationship between evapotranspiration and shoot and root dry weights increased by increasing irrigation interval which shows that in lower irrigation amounts, water use efficiency for shoot and root dry matter productions have increased. The relative reduction coefficients of shoot and root yields due to deficit irrigation were 0.28 and 0.38, respectively, it can be stated that dry matter production in root was more sensitive to water shortage compared than shoot. The salinity threshold of soil solution for reducing shoot and root dry weights for two-year pistachio seedlings of Badami cultivar were 8.8 and 6.9 dS/m, respectively. The slope for decreasing shoot and root dry matter was 4% per unit increase in soil solution salinity. The results of this study can be used for water management in greenhouses and farms for growing pistachio seedlings of Badami cultivar.

3/3/2022 12:00:00 AM

624

WSE23

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