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In order to select drought-tolerant hybrids, 18 new sunflower hybrids along with the ZARIN cultivar were evaluated in a randomized complete block design in non-stressed and drought-stressed conditions in two experimental field stations (Gorgan and Gonbad) during the 2021-2022 cropping season. Based on yield (seed yield and oil yield) in non-stress (Yp) and drought stress (Ys), various stress tolerance indices such as stress tolerance index (STI), mean productivity (MP), geometric mean productivity (GMP), harmonic mean (HM), Stress susceptibility index (SSI) and tolerance index (TOL) were calculated. The results of the combined analysis indicated that the environmental effect justified the largest percentage of all data variations. Correlation analysis between drought tolerance indices with non-stressed and drought-stressed yields showed that HM, MP, GMP, and STI indices and especially STI index were recognized as the most suitable indices for selecting drought tolerant genotypes in sunflower. The correlation between oil yield under non-stressed and drought-stressed was significant at the 5% probability level. Three-dimensional diagrams based on STI index and yield in non-stress and drought stress conditions showed that H16, H10, H2, H4, and H1 hybrids had good performance in both non-stress and drought stress conditions and were selected as the most tolerant genotypes to drought stress. Therefore, these hybrids can be used for further testing, including adaptation tests in warm wet areas. [ABSTRACT FROM AUTHOR]

Despite the high potential of sesame production in the country, its yield and water use efficiency is low. Therefore, identifying genotypes with high grain yield, especially under drought stress conditions, is essential for developing this crop. For this purpose, field experiments were conducted to investigate the qualitative and quantitative response of 21 sesame genotypes to drought stress conditions at Seed and Plant Improvement Institute, Karaj, located in the semi-arid region of Iran, during the 2017 and 2018 growing seasons. The experiment was a split-plot based on a randomized complete block design with three replications. The irrigation treatments consisting of normal irrigation and drought stress were assigned to the main plots and the sesame genotypes (20 imported genotypes with one Iranian cultivar as a control) were allocated to the sub-plots. Dongeuy, Local 123, Hail 2 and Anthalya 1 genotypes were found as early maturing, Gynum 11, Kubarez 55, Uusu 1, Songhak, Hoechon 2, Dunae, Pachequero, Haibuk and Sunhua 1 genotypes as the medium maturing, Lao hong zhi ma, Bian gan, Bukbak, Margo, Amaliada, Jungkyung and Black chil sung genotypes as the late maturing and Oltan genotype as the very late maturing group. The Margo genotype showed the highest LAI (3.2), and Sunhua 1 genotype showed the lowest value (1.0). The results also revealed that drought stress decreased the number of capsules per plant, the number of seeds per capsule and 1000-seed weight by 35, 44 and 35%, respectively. On the other hand, drought stress caused a reduction in grain and dry matter yield in all genotypes. The Dongeuy genotype with 50% reduction and Songhak genotype with 26% reduction in grain yield showed the highest and lowest sufferings from drought stress, respectively. The Margo genotype produced the highest grain yield in both irrigation treatments (1531 and 1107 kg ha-1 under normal irrigation and drought stress treatments, respectively). In conclusion, the Songhak genotype was considered as one of the superior genotypes due to its shorter growing period, less grain yield loss under drought stress, and high oil yield. [ABSTRACT FROM AUTHOR]