Evaluation the Effect of Brassinosteroid on The Improvement of Oil Quality and Yield of Rapeseed Genotypes under Late-Season Drought Stress

Drought stress is one of the most important factors in reducing yield and seed quality of rapeseed. The present study chiefly tries to evaluate the effect of application of brassinosteroid on seed yield, oil content, oil yield, and fatty acids profile of rapeseed genotypes under late-season water deficit stresseen considered. A factorial split-plot test has been conducted in a randomized complete blocks design for two cultivation years (2017-2019) in Karaj, Iran. Experimental treatments include two levels of brassinosteroid (i.e., 0 (control) and 0.1μmol) and two levels of irrigation (full irrigation (control) and withholding irrigation from flowering stage) as factorial in the main plots, and rapeseed genotypes (Nafis, Ahmadi, Okapi, Nima, and Niloufar) as subplots. The levels of oleic acid and linoleic acid in the conditions of application of brassinosteroids have been 0.7% and 11% in full irrigation conditions and 1.1% and 6.4% in withholding irrigation conditions, respectively, compared to the control on the other hand, the use of brassinosteroids in withholding irrigation conditions reduce palmitic acid by 14% compared to the control. Okapi genotype has had the highest and lowest erucic acid and grain yield in irrigation conditions, respectively. Under drought stress conditions, the highest seed yield (3112.3 kg/ha) and the lowest amount of erucic acid (0.26%) belonged to Niloufar genotype. The use of brassinosteroids in both irrigation treatments improve the quality of fatty acids and Niloufar cultivar is recommended in both irrigation conditions