Identification of EMS-induced sesame (Sesamum indicum L.) mutants with improved low-temperature tolerance during...

Sesame (Sesamum indicum L.) is a valuable oilseed crop in Morocco, but its cultivation is strictly constrained by sensitivity to low temperatures during early-season sowing. Traditionally sown in June, advancing the sowing date to April would allow farmers to capitalize on residual spring rainfall, significantly reduce irrigation dependency, and improve the crop productivity. However, this strategy exposes germinating seeds to sub-optimal soil temperatures (10-15 °C night minima). Mutation breeding via ethyl methanesulfonate (EMS) offers a powerful approach to generate novel genetic variability for abiotic stress tolerance. This study aimed to identify EMS-induced sesame mutants exhibiting superior germination and early seedling growth performance under progressive low-temperature stress conditions. Germination and seedling growth traits were assessed under controlled in vitro conditions. Low temperature stress induced highly significant genotypic variation (p<0.001) for all traits except for root and plumule length. At the coldest regime (24 °C/12 °C), mutants ML2-37 and ML2-72 maintained significantly higher germination percentages compared to the cold-sensitive mutant US1-2. The tolerant mutants exhibited faster germination rates, shorter mean germination times, superior root-shoot ratios, and higher seedling vigor indices. The mutants ML2-37 and ML2-72, demonstrating promising low-temperature tolerance during the critical germination phase, represent valuable genetic resources for developing early-sowing, climate-resilient sesame cultivars. However, since the present study was conducted exclusively under controlled laboratory conditions, the findings should be supported by an extensive field validation across multiple sites and seasons in order to confirm their agronomic performance and yield stability under real early-spring sowing conditions.