In this study， the forage oat （Avena sativa L.） cultivar ‘Zhongtian No. 4’ was used as the experimental material to establish an optimized ethyl methanesulfonate （EMS） mutagenesis system. A series of pretreatments steps were employed， including husk removal and a 30-hour seed moisture conditioning period， followed by EMS mutagenesis treatments at different concentrations and durations， and a post-treatment involving exogenous gibberellin application. An M₂ mutant population was constructed. Agronomic traits were investigated at the milk stage to evaluate the mutagenic effects and to screen the high-yielding germplasm. The results indicated that soaking seeds in 98% concentrated sulfuric acid for 6 minutes effectively removed the husk barrier of forage oat seeds. Adjusting seed moisture content to 50% via a 4-hour soaking facilitated efficient penetration of EMS into the seed. The optimal EMS mutagenesis conditions for forage oat were determined to be 1.0% EMS treatment for 16 hours. Treatment of mutagenized seeds with 50 mg·L^-1 exogenous gibberellin significantly improved seedling growth. Compared with the control without added gibberellin， the germination rate increased by 8.5%， and the seedling length also recovered to the level of the non-mutagenized seedlings. This EMS mutagenesis technique systematically addressed key limiting factors in forage oat， including seed permeability barriers， inconsistent physiological states， and mutagen-induced damage. In the M₂ generation， the mutagenic efficiency for obtaining high-yield potential germplasm reached 1.92%， and 13 elite high-yield potential germplasms were successfully identified.

Forage oat  /  EMS  /  Mutagenesis system  /  Exogenous gibberellin  /  Moisture content  /  High-yield germplasm