Effect of Brassinosteroid Application on Yield and Its Components of Wheat Genotypes Under Water Deficit Conditions

Drought is the major abiotic factor limiting crop production over the world. The present study aimed to evaluate the effects of brassinosteroid on yield and its components of seven wheat genotypes under water deficit conditions. A split-split plot design based on a randomized complete block design with three replications in the research filed of Seed and Plant Improvement Institute in Karaj at 2017-2018 and 2018-2019 cropping seasons. The main plots were two levels of water deficit (normal irrigation and irrigation cut off from flowering stage), subplots were four concentrations of brassinosteroid (0, 0.25, 0.625 and 1 mg.l-1) and sub-sub plots were allocated to six wheat genotypes (3737, 4228, 3506, 4056, 2853, Mehrgan and Parsi). The result revealed that irrigation cut off in flowering stage caused reduction in the mean values of the characters.  Also, results demonstrated that the brassinosteroid partially offset the adverse impacts of water deficit, which, application of 0.625 mg.l-1 was more effective than the other levels.  The highest grain yield (1.63 kg m-2) was obtained in 4228 genotype under normal conditions and application of 0.625 mg.l-1 of brassinosteroid, whereas the lowest (0.33 kg m-2) was observed in Parsi under water deficit and whiteout brassinosteroid.  Based on principal components analysis the three first components explained 92 of total variance among the genotypes.  According to the results of present study brassinosteroid partially offset the adverse impacts of water deficit and caused increasing in wheat yield.  Also, the results suggested that 4228 genotype can be a candidate for future wheat breeding programs to produce water deficit tolerant varieties with proper yield.