Introduction: Sesame (Sesamum indicum L.) is an annual plant and an ancient plant that has been cultivated in Asia and Africa for about 7500 years. Sesame seeds contains 40-60% oil and for this reason, it is cultivated as an oil plant in many countries. Drought is a serious problem for crop production in arid and semi-arid regions of the world. One of the most important research programs in drought management in different plants is the identification and grouping of sensitive, drought-tolerant genotypes. Mehran region in Ilam province is one of the sesame growing regions in the country. Therefore, the purpose of this study was to cultivate sesame cultivars in Mehran under drought non- stress and stress  conditions in order to identify superior cultivars in terms of yield and tolerance to drought stress.
Materials and Methods: 14 sesame cultivars were planted in the form of a split-plot design based on a randomized complete block with three replications in the Agricultural Research Farm of Ilam University in Mehran. The main factor of irrigation levels included irrigation after 100 mm of evaporation from the class a pan (conventional irrigation) and irrigation after 200 mm of evaporation from the class a pan, and the secondary factor was the studied sesame genotypes. Traits were measured based on 10 plants harvested from two central lines and taking into account the marginal effect. The measured traits were economic yield and number of capsules per plant, number of sub-branches, number of leaves, capsule length, capsule width, capsule weight and plant height. In order to determine resistant and sensitive cultivars to stress, various indices related to stress resistance were calculated.
Results and Discussion: The studied genotypes showed a significant difference in terms of the traits measured in the conditions of no stress and drought stress. The results of the table show that the effect of irrigation for the characteristics of capsule fresh weight, seed weight and capsule width showed a significant difference at the level of 1% and for capsule dry weight and plant height showed a significant difference at the level of 5%. Which indicates that the studied traits change under stress conditions. Other traits did not have significant differences. In the evaluation of tolerance to drought stress in different genotypes of sesame, plant height, biological yield and grain yield per surface unit decreased significantly with increasing drought stress intensity. According to the correlation of performance under stress (YS) and no stress (YP) conditions with drought tolerance indices, GMP, STI and MP indices have a correlation coefficient of 0.93, 0.905 and 0.853, respectively. Performance as the best indicators of drought tolerance in stress conditions and MP, GMP, STI and TOL indicators with correlation coefficient of 0.984, 0.935, 0.925 and 0.735 respectively with performance as the best indicator. The tolerances were under stress-free conditions. These indices can be used to identify genotypes tolerant to water stress with high yield. Based on this, Holeil variety is introduced as the most tolerant variety to drought stress.
Conclusion:  In water conditions, the cultivar Yellow white had the highest yield and the cultivar Nashkofa had the lowest yield. Under stress conditions, Holeil variety had the highest yield and Nazmultib had the lowest yield. GMP, STI and MP indices had the highest correlation with performance in water and stress conditions and therefore were chosen as the best indices. Based on this, Holeil variety is introduced as the most tolerant variety to drought stress.