Introduction
Sesame (Sesamum indicum L.) is an oilseed crop widely cultivated in dry and semi-arid regions. It is also among the most healthy and quality edible oil sources worldwide. With a short vegetation period, it has relatively high drought tolerance and potential for decreasing the present gap between consuming and producing the edible oil since it comprises 17–20% protein and 40–50% oil. With minimal input requirements, sesame is well-suited for crop rotation. However, research on optimal irrigation management, particularly the timing of irrigation cut-off, remains limited for existing cultivars and newly introduced lines in the Bushehr regions, a major sesame production hub. This study hypothesizes that optimizing water availability during non-critical growth stages can improve irrigation water productivity while maintaining seed and oil yields.
 Materials and Methods
The experiment was carried out during the 2022 and 2023 growing seasons at the Agricultural and Natural Resources Research Center in Borazjan, Bushehr, Iran. The region has a hot and arid climate with an average annual precipitation of 250 mm, primarily occurring in autumn and winter. The study examined two irrigation regimes: full irrigation (80 mm evaporation) and low irrigation (160 mm evaporation), and three irrigation cut-off timing: at the beginning of flowering, the beginning of capsule formation, and mid-capsule formation, and two sesame genotypes.  Dashtestan 2 cultivar and promising line 7, were evaluated for yield components, seed oil content, oil yield, and irrigation water productivity. A split-split-plot design was used, with irrigation regime as the main plot, irrigation cut-off timing as the sub-plot, and genotype as the sub-sub-plot, arranged in a randomized complete block design with three replications. SAS software (version 9.4) was used to analyze variance on the data. Because Bartlett’s test showed homogeneity of variance in most of the studied traits, data were subjected to combined analysis of variance. Differences between the main effects of treatments were compared using the protected LSD at the 0.05 probability level when the F-test was significant. The slicing method was used to separate the significant interaction effects
 Results and Discussion
As anticipated, reduced water availability under the low irrigation regime significantly decreased seed yield components in both genotypes. However, line 7 outperformed Dashtestan 2 in key yield traits, including the number of capsules per plant and seeds per capsule, particularly under full irrigation, while showing greater resilience to reduced irrigation and earlier irrigation termination. Conversely, Dashtestan 2 exhibited a higher thousand-seed weight. Line 7 showed higher average seed yield across irrigation treatments, and did not require irrigation beyond the early capsule formation to reach its maximum yield, enabling a water saving of at least 600 m ³ha^-1 without significant yield reduction. While both genotypes exhibited similar maximum irrigation water productivity, Dashtestan 2’s efficiency gains resulted from lower water use, whereas line 7 combined water savings with a satisfactory yield (733 kg ha^-1) when irrigation was cut-off at the capsule-formation stage. Although Dashtestan 2 exhibited a slightly higher seed oil content (up to 1.5%), line 7 produced up to 24% more oil yield.
 Conclusion
Replacing older sesame cultivars with improved lines, combined with optimized irrigation management, can enhance water productivity, reduce water consumption, and minimize yield losses.