The effect of epibrassinolide on growth and seed yield of bean under optimal irrigation and drought stress conditions

In order to evaluate the increment possibility of bean seed yield by the application of brassinosteroid, a split factorial experiment was conducted based on randomized complete block design with three replications at the research farm of Agriculture Faculty, the University of Zanjan during the 2016-2017 cropping season. In this experiment, irrigation levels included optimal irrigation and drought stress were applied to main plots and bean cultivars including Kusha cultivar and COS16 genotype, and four levels of brassinosteroid including of no-application (control), two, four and six μM were allocated to subplots as factorial. Drought stress was applied at the flowering stage, and bean plants were sprayed with brassinosteroid (epibrassinolide) simultaneously with drought stress. The results showed that drought stress decreased leaf area index, yield components, seed yield, biological yield and harvest index and the application of epibrassinolide minimized the negative effects of drought stress and increased in the above traits. The highest seed yield was obtained by application of two μM of epibrassinolide with an average of 2068.2 kg.ha-1. Also, among the studied cultivars, the Kusha cultivar under optimal irrigation with an average of 3025.45 kg.ha-1 showed a higher seed yield compared to COS16 genotype. Therefore, the use of epibrassinolide can be suggested as a solution to increase drought stress resistance and enhance seed yield of bean under optimal irrigation and drought stress conditions.