Exploring mechanisms of drought-tolerance and adaptation of selected sesame mutant lines

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

First Study of Improved Nutritional Properties and Anti-Oxidant Activity in Novel Sesame Mutant Lines as Compared to Their Wild-Types

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

Moroccan sesame: Current situation, challenges, and recommended actions for its development

Sesame (Sesamum indicum L.) is one of the most recommended oil crops due to its nutritional and medicinal properties. It is a tropical and subtropical plant; however, it is also cultivated in arid and semi-arid regions, including Morocco. Nevertheless, the sesame crop in this country faces many constraints and challenges that restrict its production potential. The objective of this study is to present the situation of sesame production in Morocco during the last twenty years by describing and discussing the seed production, the harvested area, the value of imports, and the most important challenges. Also, some relevant strategies and measures to counteract these constraints and, thus, improve sesame production have been proposed and discussed. To make a fair diagnosis, a survey was carried out among 33 sesame producers in the Tadla area, in addition to the national and international databases that were consulted. The results showed that sesame area and production dropped markedly between 2000 and 2020. As a result, the import quantities and values have been significantly and gradually increased during the same period. The observed decline in both the area and the production may be due to several constraints including recurrent drought, restricted supply in irrigation water, poor cultural practices, low-yielding cultivars, and pests and diseases. Therefore, there is an urgent need for scientific research in terms of breeding to develop and release high-performing and adapted varieties and crop management to find and adopt the best cultural practices. Besides, sesame producers should organize themselves in associations or cooperatives to ensure an added value of their production and improve their profit margin and income. All these actions and measures would be able to promote and develop the sesame sector in Morocco to meet and satisfy the high domestic and global demand for this precious and valuable seed

Assessment of Novel Genetic Diversity Induced by Mutagenesis and Estimation of Genetic Parameters in Sesame M₄ Mutant Lines

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

Drought-tolerant sesame mutant lines assessed by physiological traits and stress indices under water deficit conditions

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

Evaluation of rapeseed (Brassica napus L.) genotypes for tolerance to PEG (polyethylene glycol) induced drought at germination and early seedling growth

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