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Deficit irrigation systems have been considered as practical strategies to overcome shortage of irrigation water in arid and semiarid regions. To assess the response of grain sorghum [Sorghum bicolor (L.) Moench] to deficit irrigation and whether arbuscular mycorrhizal fungi (AMF) can moderate drought stress influence on grain yield, a 2-yr field experiment was conducted using split-split lay out on a randomized complete block (RCB) design. Irrigation (full and deficit) was assigned to the main plots. Subplots were allocated to two genotypes (Kimiya and Speedeh) and P sources viz: no fertilizer, sole chemical P fertilizer, seed inoculation with AMF and combined fertilizer (50% of the chemical P fertilizer + AMF) were assigned to the sub-subplots. Results indicated that deficit irrigation reduced grain yield of Kimia and Speedeh by 16 and 26%, respectively, while improving their irrigation water use efficiency (IWUE). Grain yield adjustment by sorghum to water stress was mainly through reducing the number of grains per panicle rather than grain mass. Application of all forms of P fertilizer improved grain yield of sorghum; however, under drought stress, plants were more responsive to combined fertilizer and used irrigation water more efficiently. The root colonization percentage was greater in Kimiya than Speedeh under full and deficit irrigation, however, both genotypes showed a lower degree of root colonization under drought conditions. Application of combined fertilizer could be considered as an alternative to chemical P fertilizer when irrigation water is limited.

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Core Ideas Deficit irrigation conditions decreased safflower seed and oil yield.Safflower cultivars demonstrated different reactions drought stress.Sina and Faraman cultivars had higher seed oil content across all irrigation treatments.Highest oil yield across all irrigation treatments was produced by Sina cultivarHarvest time deferment was associated with increased oil oxidation in all cultivars. Drought stress significantly declines crop yield. Efficient soil moisture management and its consequent effects on metabolic changes which happen in response to drought stress are important in dry regions agriculture. This research was performed to evaluate yield, yield components, and oil accumulation in safflower (Carthamus tinctorius L.) cultivars seed in response to water deficit conditions. A field experiment was conducted at the Research Farm of the College of Agriculture, Tabriz University during two growing seasons of 2014 and 2015. The treatments were arranged as split plots based on randomized complete block design with three replicates. Irrigation treatments (irrigation after 70, 100, 130, and 160 mm evaporation from class A pan) were assigned to the main plots and spring safflower cultivars (Faraman, Goldasht, Sina, and Soffeh) were allocated to the subplots. Safflower seeds were harvested in 5‐d intervals at seven stages during development and maturity period. The result showed that Sina cultivar had the highest seed yield per unit area. Maximum oil percentage of safflower seeds was obtained at 1 to 12 d after plant physiological maturity. Water stress caused seed oil percentage decline across all cultivars. Sina and Faraman cultivars had higher oil percentage across all irrigation treatments. The highest oil and seed yield per unit area under both full and limited irrigation conditions was produced by Sina cultivar. Drought stress decreased seed yield, yield components, and oil content across all safflower cultivars, however, the extent of the damage was limited due to cultivar genetic characteristics and ecological origin.