Abstract
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.
Highlights
Sesame (Sesamum indicum L.) is known as “the queen of oilseeds” due to the high oil content and nutritional quality that characterize its seed [1]
Under severe drought (−1.2 MPa), seed germination was completely inhibited in genotypes “US06”, “US2-6”, “US2-1”, “US1-2”, “ML13”, and “ML2-68” (Figure 1B)
Our results showed that germination rate (GR) decreases significantly with water deficit, which is in agreement with the results of El Harfi et al [20] and Bakhshandeh et al [38] in sesame
Summary
Sesame (Sesamum indicum L.) is known as “the queen of oilseeds” due to the high oil content and nutritional quality that characterize its seed [1]. In arid and semiarid areas, drought often occurs conjointly with heat or high temperatures and impairs sesame production significantly [2,3]. Severe or prolonged drought adversely influences sesame productivity by reducing the number of capsules per plant, the yield, and the quality of the oil [11,12,13]. There is a need to improve crop tolerance to drought by breeding and selecting appropriate germplasm to be used for the development of adapted cultivars that could enable sustainable and competitive sesame cultivation in arid and semiarid environments. Just a few studies have been carried out on sesame tolerance to drought during germination and early seedling growth stages by using and investigating different genotypes [8,11,12,19,20]. To our knowledge, only one study has been performed on sesame mutants that were obtained through gamma-ray treatment [8]
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