Water scarcity is a critical factor that restricts crop production, and projections indicate that its severity will escalate in the future due to the impacts of global warming. The objective of this research was to assess the role of MnSO4 in improving water deficit tolerance in two sesame cultivars, Dashtestan2 and Naz Takshakheh. A factorial pot study was conducted based on randomized complete block design with three replications at the Research Greenhouse of the Faculty of Agriculture, University of Ilam in 2019. MnSO4•7H2O was utilized via seed priming, foliar application, or a combination of both methods. Three different water level regimes were established: 75% field capacity (FC) representing well-watered conditions, 50% FC indicating mild water stress, and 25% FC denoting severe water stress. The results of experiment indicated that cultivar Dashtestan2 produced a greater seed yield compared to the Naz Takshakheh cultivar, under both well-watered and water-deficient conditions. Foliar application was more effective than seed priming in promoting proline accumulation and enhancing the activities of catalase and ascorbate peroxidase enzymes. Plants treated with both seed priming and foliar application with MnSO4•7H2O demonstrated enhanced antioxidant enzyme activity and higher seed yield. Based on the results, the application of manganese sulfate through seed priming, foliar application, and a combination of both techniques led to a notable increase in seed yield for both sesame cultivars facing water deficit stress. The Dashtestan2 cultivar showed especially significant improvements in seed yield, which can be attributed to increased activity of antioxidant enzymes and osmotic regulators. Among the various methods for applying manganese sulfate, the combination of seed priming and foliar spraying demonstrated superior effectiveness in enhancing tolerance to water deficit stress.
