Effect of deficit irrigation regimes on photosynthetic, morpho-physiological and yield traits of safflower (Carthamus tinctorious L.) in Ahvaz climate condition

Deficit irrigation is a water management strategy that reduces water use to the drought sensitive growth stages. In order to study of different deficit irrigation regimes on photosynthetic, morpho-physiological and yield traits of two safflower cultivars, a field experiment was carried out in a split plot arrangement in randomized complete block design with three replications in the research farm of Shahid Chamran University of Ahvaz in 2017-2018. Main plots consisted of four irrigation regimes including; Control (irrigation treatments: 80%, 80%, 80%, and 80% of field capacity), mild deficit irrigation (irrigation treatments: 60%, 80%, 80%, and 40% of field capacity),  moderate deficit irrigation (irrigation treatments: 60%, 60%, 60%, and 60% of field capacity) and severe deficit irrigation (irrigation treatments: 40%, 60%, 60%, and 60% of field capacity), and sub plots consisted of two safflower cultivars including; Padideh and Goldasht. Deficit irrigation treatments were applied at stem elongation, branching, flowering, and grain-filling stages. There was a significant difference between cultivars in terms of most traits and irrigation regimes differently caused a significant reduction in stomatal conductance, photosynthetic rate, number of head per plant, number of grain per head, number of grain per plant, 1000 grain weight, head diameter, height of first secondary branch, plant height, number of secondary branch per plant, biomass yield, harvest index, and grain and oil yield. The grain yield of the both cultivars significantly reduced under mild, moderate and severe water-deficit stresses by 26, 39 and 63%, respectively, relative to the control. The reductions were 31, 43 and 63%, respectively, compared to the control in oil yield. Goldasht showed higher oil yied due to it’s higher grain yield compared to Padideh. Totally, moderate deficit regime as a suitable strategy  of water management to reduce water use and Goldasht cultivar cultivation is defined in this area.