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Sesame (Sesamum indicum L.) is an important oilseed crop, but its productivity and quality are often compromised by drought stress. Developing drought-resistant sesame varieties is thus crucial for its sustainable cultivation. In this study, we conducted a comprehensive investigation of morphoanatomical and physiochemical mechanisms underlying drought tolerance in selected sesame mutants. The drought-tolerant mutants ‘ML2-37’ and ‘ML2-72’ were compared to the susceptible mutant ‘US1-2’ and the parental cultivar ‘ML13’ under controlled greenhouse conditions. Our results showed that the tolerant mutants exhibited superior performance in response to drought stress. We identified specific adaptation mechanisms, including accumulation of proline, glycine, and cuticular wax, which contribute to maintaining optimal water status. Additionally, the tolerant mutants showed a significant reduction in the number and diameter of the xylem vessels, even under severe stress. These results open up good perspectives for the development of drought-resistant sesame varieties, thus offering a promising solution to improve agricultural productivity in regions affected by increasing water scarcity in the actual context of climate change. The selection indices proposed in this study provide practical tools to identify and develop sesame germplasm and cultivars adapted to drought stress conditions. This work constitutes a significant contribution to research on drought tolerance in sesame and offers promising prospects for sustainable agriculture in the context of global climate change.

Sesame (Sesamum indicum L.) is an ancient oilseed, aromatic, and medicinal crop widely used for its high-quality oil and seeds. The available genetic diversity in Morocco is too limited; thus, a mutagenesis breeding program was adopted. This study was carried out to evaluate the novel variability induced and observed in 11 M4 mutant lines and to estimate some valuable genetic parameters. The experiment was conducted in two different environments using a randomized complete block design with three replications. Phenological, morphological, and agronomic traits were recorded. To estimate the effect of genotype, environment, and their interaction, ANOVA and planned contrast analyses were performed. To examine relatedness among genotypes, cluster analysis was performed. Significant differences among mutants and between parent cultivars and their respective mutant lines were observed. Genetic parameters such as genotypic (GCV) and phenotypic (PCV) coefficients of variation, broad-sense heritability (H2 b.s), genetic advance (GA), and genetic advance over the mean (GAM) were high in most traits. Highly productive mutants, ‘US2-1’ and ‘US1-2’, were observed, exhibiting the highest number of capsules per plant and seed yield ever reported. Additionally, there are other promising mutants with early flowering, early maturity, and a reduced height of the first capsule. This suggests that mutagenesis can be successfully applied to develop high-yielding sesame varieties along with other improved phenological and agromorphological traits. All these mutant lines can be used as promising germplasm to develop competitive sesame cultivars to meet the increasing demand for sesame oil and seeds in the actual context of climate change.