Effect of brassinosteroid foliar application on yield improvement, yield components and some biochemical characteristics of wheat (Sirvan number) under drought stress

In this research, the effect of foliar spraying of brassinosteroid (0, 0.077 and 0.384 mg/liter) on grain yield and some physiological characteristics of wheat (Sirvan cultivar) under drought stress conditions (100% control) and 50% F.C.) was investigated in a factorial arrangement based on a randomized complete design with four replications at the research greenhouse of the Agriculture faculty, Shahid Bahonar University of Kerman on 2016. The results showed that drought stress caused a significant reduction in the biomass, yield and yield components of wheat and the decrease of these traits compared to the control was 31.7%, 29.6% and 20.3% respectively. On the other hand, brassinosteroid foliar spraying caused a significant increment of biomass, yield and yield components by approximately 22.7%, 22.4% and 12.5%, respectively, compared to the plants which were treated with distilled water under stress conditions. Drought stress had a significant effect on increasing of antioxidant enzymes activity (peroxidase, ascorbate peroxidase, catalase and superoxide dismutase) and the concentration of malondialdehyde, hydrogen peroxide, as well as the accumulation of carbohydrates and proline in wheat leaves. Spraying of brassinosteroid in both stress and non-stress conditions increased the activity of antioxidant enzymes and osmolytes accumulation (protein, carbohydrate and proline) and conversely reduced the amount of hydrogen peroxide and malondialdehyde, and this effect was more noticeable under drought stress condition. It seems that the effect of brassinosteroid application on modulating drought stress and improving wheat yield can be related to enhancement of osmotic regulation (through the accumulation of osmolytes) and increasing the activity of the antioxidant defense system mechanism in wheat.