Evaluation of yield and some traits of two safflower (Carthamus tinctorius L.) cultivars under different irrigation regimes

Introduction Abiotic stresses are most important limiting factors to crop productivity that can reduce the yield of plants up to 70 percent. Drought is the most important stress and decreases the yield of plants in world. Safflower (Carthamus tinctorius L.) is a multipurpose oilseed crop grown mainly for its high quality edible oil, bird seed, coloring and flavoring food, in textile dyes, as livestock forage, as a vegetable, in herbal teas, and for medicinal purposes. It is resistant to cold, drought, and salinity stress. Therefore, it can be grown successfully on dry land and in surrounding regions which have insufficient precipitation. The aim of this experiment, was evaluated of yield and yield components of two safflower under optimal irrigation and drought stress conditions.   Materials and methods The current experiment was carried out at the Research Farm of the Faculty of Agriculture, Zanjan University, Zanjan, Iran (36410N, 48290E) in spring 2010 and 2011 years. The experiment was laid out in split factorial experiment was conducted based on randomized complete block design with four replications. Experimental treatments included optimal irrigation (-0.5 MPa) and drought stress (-2 MPa) and were two spring safflower cultivars (Goldasht and Zendehrood). Each plot consisted of four rows, each measuring 6 m long, distance of each rows and plants was 50 and 10 cm, respectively. After thorough establishment of plants, at the 3 fold 4 leaves stage, irrigation treatments (-0.5 MPa and -2 MPa) was applied. In order to apply irrigation treatments, irrigation was stopped until the soil water potential reached -0.5 and -2 MPa for optimal and  drought stress respectively, then re-irrigation was performed. At the physiological maturity stage, plants in an area of 1 m2 to measuring of number main capitul, number seed in main capitul and weight of thousand seeds, and area of 2 m2 for biological yield and grain yield were harvested, then all aboveground dry matter were determined.   Results and discussion The effect of irrigation treatments, cultivar and year not significant on diameter capitul, number of main and lateral capitul in plant. The year has significant effect on all traits such as Capitul diameter.  The irrigation treats has not significant effect on capitul diameter, number main and lateral capitul, number seed in main lateral capitul and oil percent. The highest of thousand weight seed (35.5 g), grain yield (214.42 kg/ha), biological yield (9600.1 kg/ha), harvest index (25.6 %) and oil yield (634.6 kg/ha) obtained in optimal irrigation, and in other traits, was not difference between optimal irrigation and drought stress. The number main and lateral capitul, number seed in main lateral capitul, biological yield, oil percent and oil yield was different between cultivars. The maximum of number of seed in capitul, biological yield, oil percent and oil yield were obtained in zendehrood cultivar, and in other traits there was not difference between Zendehrood and Goldasht. Grain yield and oil yield reduced under drought stress amount 51 and 65 percent, respectively. Oil percentage in optimal irrigation was 8 percent more than drought stress condition. Grain yield, oil percentage and oil yield of Goldasht cultivar 7, 8 and 26 percent were higher than Zendehrood cultivar, respectively.   Conclusions According this result, yield and related traits of yield extremely affected by climate conditions each of year. Thus, success in agriculture under field condition, extreme dependent to feature of climate. The Goldasht cultivar has higher of grain yield (7.5 %), oil percent (20.44 %) and Oil yield (26.19 %) than Zendehrood cultivar. In normal and drought stress conditions, the results of current experiment showed that Goldasht cultivar was superior to Zendehrood cultivar, and is more tolerant to drought stress, therefore suggested that cultivate Goldasht cultivar in deficit conditions.