Effect Brassinosteroid application on safflower cultivars tolerance to water stress in Ardabil

Safflower is cultivated for a long time in the past. This plant tolerates drought and salinity stress. Water limitation restricted the crop production in many parts of the world, especially in arid and semi-arid regions. The aim of this study was to select proper varieties of safflower in water limited conditions of cold regions and increase plant tolerance to this stress. Introducing of physiological traits associated with the water stress tolerance in safflower can be useful in selecting the appropriate cultivars in water scarce regions. Since the safflower is one of the important oil seeds, so this plant selected in this study.
In order to investigate the effect of water deficit stress on some physiological traits of safflower, an experiment carried out in Agricultural Research Station of University of Mohaghegh Ardabili in 2014, as split plot factorial based on randomized complete block design with three replications. The main factor was three irrigation schedules as irrigation after 80, 120 and 150 mm evaporation of the class A pan, and subplots, were three cultivars of safflower (Goldasht, Spiny Sina and Faraman) and two levels of Brassinosteroid (control and 10 -7 M).
Based on results there was no significant interaction between irrigation and cultivar in photochemical efficiency of PSII (fv/fm). Interaction of cultivars and irrigatin schedules was significant on chlorophyll a, b and total chlorophyll, FO and Fm, relative water content and water saturation deficit, proline, soluble sugars and leaf protein. At severe stress (irrigation after 160 mm evaporation), Faraman cultivar had the highest soluble sugars, relative water content, chlorophyll a and total chlorophyll. Spiny Sina cultivar had the highest chlorophyll water saturation deficit and Goldasht had the highest content of proline and fo. In the sever stress ( 160 mm evaporation) fm of Goldasht and Faraman was placed in one statistical group and both had more fm than Sinaspiny and in leaf soluble protein, spinySina and Faraman with equal statistical group were superior to Goldasht. Simple effects of drought stress, cultivar and Brassinosteroid were significant in all studied traits. The main effects of water deficit showed that increasing water stress leads to elevated levels of proline, soluble sugars, water saturation deficit and the fo and fm. In contrast, the chlorophyll a, b, total chlorophyll content, relative water content, Fv/Fm, and soluble protein were reduced. Applying Brassinosteroid, resulted in a significant increase of chlorophyll a, b, total chlorophyll content, relative water content, fm, proline and soluble protein, but there were a decrease in soluble sugar, water saturation deficit, Fo and Fm.
It is concluded that in cold regions like Ardabil Faraman cultivar will have better growth in dry conditions than Goldasht and the spiny Sina is not suitable for the cultivation in the Ardebil region. Also, Brassinosteroid improved water content and caused more growth under water deficit stress