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Aujourd’hui, les événements extrêmes provoqués par le changement climatique, conjugués à l’augmentation de la population mondiale, menacent sérieusement la sécurité alimentaire à travers le monde. La sécheresse est particulièrement préjudiciable à la production agricole, notamment aux cultures oléagineuses. Ce stress hydrique est devenu structurel au Maroc et accentue le problème de souveraineté alimentaire en huiles alimentaires. Il existe cependant une volonté politique de promouvoir et de développer les oléagineux pour améliorer les revenus des agriculteurs et assurer la souveraineté alimentaire en huiles de graines en augmentant la production nationale. Dans ce contexte, l'INRA, en tant qu'établissement public de recherche, s'engage à jouer un rôle à travers une stratégie de recherche adaptative et prospective incluant notamment l'approche génétique. Avec le changement climatique au Maroc, les agriculteurs doivent cultiver des variétés de colza, de tournesol et de sésame tolérantes à la sécheresse et aux températures élevées, ainsi que d'autres cultures alternatives plus résilientes à ces stress abiotiques. La diversification et le développement de cultures d’oléagineux adaptées et résilientes ainsi que l’adoption d’un large éventail de cultivars tolérants sont d’une importance capitale pour lutter contre le changement climatique et améliorer la souveraineté alimentaire en matière d’huiles comestibles. Ce chapitre se veut une synthèse de la stratégie de l'INRA pour la valorisation et la résilience des cultures oléagineuses dans le contexte actuel de changement climatique, avec une présentation et une discussion des réalisations marquantes pouvant jouer un rôle dans le développement de cette filière au Maroc. L'accent sera mis sur les mutants prometteurs du colza et du sésame récemment développés par mutagenèse chimique à l'INRA-Maroc. Les implications de ces réalisations ainsi que les perspectives de recherche sur les mécanismes de tolérance à la sécheresse et l'utilisation de nouvelles technologies pour des mutations ciblées sont également discutées.

Rapeseed (Brassica napus L.) is an important oilseed crop well adapted to Mediterranean area. However, increasing drought, due to climate change, impairs its growth and development, mainly when this stress occurs early during germination. This study carried out in vitro conditions aimed to investigate the effect of water deficit on seed germination and seedling growth traits in 12 genotypes to select the most drought-tolerant ones. Drought conditions were created using polyethylene glycol 6000 to induce three osmotic potential levels, namely −0.7 MPa for moderate stress, −0.9 MPa for intermediate stress, and −1.1 MPa for severe stress. Germination percentage (GP), germination rate (GR), mean germination time (MGT), root length (RL), shoot length (SL), root-to-shoot ratio (RSR), seedling vigor index (SVI), shoot elongation rate (SER), and root elongation rate (RER) were measured/calculated. ANOVA and PCA were performed to analyze the data gathered. Results showed a significant effect of genotype, drought, and drought × genotype interaction on all studied parameters. Under severe drought conditions, overall values of GP, GR, RL, SL, SER, RER, and SVI decreased by 87.15 %, 53.29 %, 9.33 %, 4.73 %, 78 %, 82 %, and 96 %, respectively, while those of MGT and RSR increased by 56 % and 76 %, respectively, when compared to unstressed conditions. However, the genotypes studied reacted differently to the three levels of water stress. Based on PCA results, RL, RER, and GP proved to be the most discriminating of drought-tolerant genotypes. Overall, higher drought tolerance was associated with higher values in RL, SL, and SVI. Accordingly, the variety ‘Nap10’ and, to a lesser extent, ‘Baraka’ and ‘Nap9’ exhibited higher drought tolerance than the rest of genotypes, which makes them potential cultivars for dry areas. However, further studies in real field conditions are needed to confirm their tolerance to drought occurring at germination as well as during other stages, mainly flowering.

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.

Climate change and water scarcity are the most important factors that affect crop production in dry areas. Sesame (Sesamum indicum L.) is a very ancient oilseed crop cultivated in arid and semi-arid regions and therefore its productivity is limited under drought conditions, which makes the selection and development of drought-tolerant cultivars imperative. This study aims to evaluate the responses to drought stress of eleven M4 sesame mutants, in addition to their two wild-type parents, cultivated in two contrasting environments. Drought stress was applied, under field conditions, by reducing the amount of irrigation water supplied by half, compared to the control. Physiological traits and various drought indices were measured/calculated. All data were subjected to analysis of variance and unweighted pair group method with arithmetic mean (UPGMA) to classify genotypes as drought sensitive or drought tolerant. Significant variations among genotypes were observed in their reactions to water regimes and environments. Overall, under water stress, proline content and stomatal resistance significantly increased, while chlorophyll content, seed yield, and relative water content significantly decreased in stressed plants. Drought indices revealed substantial differences among genotypes, with tolerant ones showing the best scores. Furthermore, correlation analysis demonstrated significant associations between physiological traits and drought indices. In light of all the traits/indices investigated, the mutant ‘US1-2’ was found to be very drought-sensitive, although it performed best under full-irrigation conditions. In contrast, the mutant lines ‘ML2-37’ and ‘ML2-37’ proved to be highly drought-tolerant and, therefore, they can be handled as an elite germplasm for the development of resilient cultivars adapted to arid and semi-arid regions where irrigation water is a limiting factor. This work constitutes a significant contribution to research on sesame drought tolerance and offers promising prospects for this crop 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.

Sesame seed represents a reservoir of nutritional components with many medicinal properties. With the current trend to increase both seed yield and nutritional quality, the cultivation of new high-quality sesame varieties is a necessity to improve human health and promote the economic efficiency of this crop. However, research efforts for the development of cultivars of high nutritional quality are too scarce. In this study, we evaluated the nutritional value and antioxidant activity of seeds of selected M3 sesame mutants, in comparison with their two wild-type cultivars. The measurements included ash, proteins, crude fibers, sugars, total phenolic content (TPC), total flavonoid content (TFC), total anthocyanin content (TAC), lignans and free radical scavenging activity (FRSA). The results show higher FRSA, TPC, TAC and lignans in the mutant “US2-6”, compared to the wild type “US06”. Besides this, seeds of the mutant “US1-DL” are rich in ash and sugars, while high protein and fiber contents were found in the mutants “ML2-5” and “US2-7”, respectively. This work highlights the possibility of improving the nutritional value of sesame germplasm through mutagenesis. The valuable germplasm obtained will be used in the sesame breeding program to develop cultivars with high nutritional quality and antioxidant activity, which could contribute to the prevention of diseases related to free radicals and nutritional deficiencies.

In the context of climate change and water scarcity, there is a need to develop and use drought-tolerant sesame cultivars. This study was conducted to evaluate the response of 13 sesame genotypes, including 11 mutants and their wild-types, to drought during germination and early seedling growth. Moderate and severe drought stress was simulated by applying polyethylene glycol (PEG) at two osmotic potentials, −0.6 MPa and −1.2 MPa, respectively, on seeds of two successive mutant generations, M2 and M3. The parameters measured or calculated were germination percentage (GP), germination rate (GR), mean germination time (MGT), root length (RL), shoot length (SL), root to shoot ratio (RSR), and the seedling vigor index (SVI). Results showed the significant effect of genotype, drought, and drought × genotype interaction on all parameters investigated. Under severe drought, seeds of seven genotypes, including wild types, were not able to germinate. There was a drastic decline of all parameters for the rest, except MGT and RSR, which markedly increased. Interestingly, two mutants, “ML2-5” and “ML2-10”, were identified as the most tolerant to severe drought and the most stable over both generations. The present work is the first report of sesame germplasm with such a high level of tolerance to drought during germination and early seedling growth stages.