Parisa Ghahramani - Department of Agronomy, Faculty of Agriculture, Urmia University, Urmia, Iran
Soleiman Mohammadi - Seed and Plant Improvement Research Department, West Azarbaijan Agricultural and Natural Resources Research Center, AREEO, Urmia, Iran
Hashem Hadi - Department of Agronomy, Faculty of Agriculture, Urmia University, Urmia, Iran

In order to investigate the effect of water treatment and nitrogen fertilizer application on remobilization and grain yield of bread wheat cultivars, an experiment was carried out as split-split plot design based on randomized complete blocks with three replications. Three levels of irrigation (full irrigation, withholding irrigation at heading, withholding irrigation at anthesis) were assigned to main plots, different times of nitrogen fertilizer application (application of ۱۲۰ kg/ha nitrogen in four different times: ۲۰ kg at sowing + ۱۰۰ kg/ha at tillering, ۲۰ kg at sowing + ۱۰۰ kg/ha at bolting, ۲۰ kg at sowing + ۵۰ kg at tillering + ۵۰ kg at bolting, ۲۰ kg at sowing + ۵۰ kg at tillering + ۵۰ kg at heading) were randomized in sub-plots and five bread wheat cultivars (Zarrin, Pishgam, Urum, Zare, Mihan) were assigned to sub-sub-plots. Withholding irrigation at different developmental stages of wheat increased remobilization percentage of all cultivars. However, application of nitrogen at the heading stage reduced remobilization. The highest and lowest remobilization were recorded for Urum and Zarrin with ۶۲.۱۳% and ۲۰.۳۳%, respectively. Grain yield was significantly reduced with the reduction of water availability. Mean grain yield of all cultivars was ۷.۵۰۰ ton/ha under full irrigation, which reduced to ۶.۵۰۰ ton/ha when irrigation was withheld. Nitrogen fertilizer applicationimproved the grain yield of wheat cultivars. The highest grain yield was obtained for Mihan by ۹.۳۹ ton/ha under full irrigation and nitrogen application at sowing + tillering + heading. The higher grain yield of tolerant cultivars under water deficit treatments was attributed to remobilization of unstructured carbohydrates from shoot to grain. It seems that selection of cultivars with higher translocation of dry matter and contribution of pre-anthesis assimilates in grain filling under water stress, can be a suitable strategy to produce high yielding cultivars under water deficit stress condition.

Fertilizer, Grain Yield, Remobilization, Water treatment, Wheat