This study aimed to investigate the effects of drought stress at the flowering stage on the physiological and molecular responses of the genes involved in the brassinosteroid pathway of two chickpea cultivars (ILC1799: drought tolerant, and ILC3279: drought sensitive). The drought resulted in significant reductions in chlorophyll a, chlorophyll b, total chlorophyll and carotenoid content in both cultivars, and had significantly lesser effects on the tolerant cultivar, Samin, compared to that of ILC3279. However, the relative water content, the osmotic potential and the cell membrane stability were less affected by drought in both cultivars. The proline content and peroxidase activity increased significantly under drought stress in both cultivars, with a higher amount in Samin (ILC1799). Members of the BES1 family positively mediate brassinosteroid signaling and play an important role in regulating plant stress responses. The expression of these genes was analyzed in chickpea cultivars under drought. Further, a genome-wide analysis of BES1 genes in the chickpea genome was conducted. Six CaBES1 genes were identified in total, and their phylogenetic tree, gene structures, and conserved motifs were determined. CaBES1 gene expression patterns were analyzed using a transcription database and quantitative real-time PCR analysis. The results revealed that the expression of CaBES1 genes are different in response to various plant stresses. The expression levels of CaBES1.1, CaBES1.2, CaNAC72 and CaRD26 genes were measured by using qRT-PCR. The relative expression of CaBES1.2 in the drought conditions was significantly downregulated. In contrast to CaBES1.1 and CaBES1.2, the expression of CaRD26 and CaNAC72 showed a significant increase under drought stress. The expression of CaRD26 and CaNAC72 genes was significantly higher in the Samin cultivar compared to that of ILC3279 cultivars.
