Effect of different irrigation regimes in different growth stages on yield, yield components and some physiological traits of wheat cultivars in Aran va Bidghol province

Introduction Drought stress, as the most important abiotic stress, plays an important role in reducing crop production. Wheat is the most important crop in Iran. In arid and semi-arid regions, it is very important to obtain cultivars that have more tolerance to water limitation and water deficit irrigation. By achieving such cultivars and determining their tolerance to low irrigation, it is possible to prevent the loss of water resources to a large extent and at the same time obtain a suitable yield in the conditions of water limitation. Although genetic improvements in grain yield under favorable and stress conditions have been clearly seen over the past few decades, the search for genetic differences and more effective selection criteria, especially under stress conditions, should be continued. Investigating the effects of different irrigation regimes in different phonological stages on wheat grain yield and introducing the best irrigation regime for this crop in the dry weather conditions of Aran Va Bidgol region are the main aims of this research. Materials and methods In order to evaluate the effect of drought stress on yield, yield components and some physiological traits of three bread wheat cultivars, the experiment was conducted during 2013-2014, in Aran va Bidgol province. A split factorial experiment based on randomized complete block design with three replications was used. The main plots considered irrigation regimes (irrigation after 60, 95 and 130 mm cumulative evaporation from class A evaporation pan), and sub-plots considered two growth stage (from elongation to heading and from heading to ripening) and three wheat cultivars (Sepahan, Roshan Back-Cross and Kavir) as factorial. Sowing was done by hand with a density of 400 seeds per square meter. Weeds were controlled by mechanical method. In the stages of elongation, heading, pollination and grain filling, the amount of water consumed in each irrigation was estimated for the main plots and was introduced to the plots during irrigation. The SPSS software was used to analyze the data. If the effect of the experimental factor was significant, the LSD test was used at the 5% probability level to compare the means. Results and discussion Results showed that delay in irrigation from 60 to 130 mm cumulative pan evaporation significantly reduced plant height, number tiller, yield and yield components, harvest index, relative water content, leaf chlorophyll content and increased the wax of coticule and water use efficiency. Irrigation after 90 and 130 mm cumulative evaporation from class A evaporation pan decreased grain yield 12 and 41.8 percent compared controlled, respectively. The reduction of water consumption in mild and severe stress treatments compared to the control treatment was 20 and 43%, respectively. Applying drought stress from the heading to ripening, led to a greater decrease in grain yield and harvest index compared to applying stress from the elongation stage to heading. The Kavir, Sepahan and Back-cross Roshan cultivars had the highest to the lowest grain yield, with 3941, 3868 and 3757 kg. ha-1, respectively. The Kavir cultivar had low plant height, high the wax of coticule (both control and stress conditions), resume high relative water content (both control and stress conditions), high leaf chlorophyll content, harvest index and water use efficiency, caused to higher grain yield. Conclusion It was concluded that by irrigation the Kavir wheat cultivar after 95 mm cumulative pan evaporation from elongation to heading, water could be saved by 20% with 12% loss in grain yield under these conditions.