Optimization of post-ripening treatments for efficient germination of early-harvested winter wheat seeds under speed breeding.

Speed breeding (SB) can substantially shorten crop generation cycles; however, premature harvest often results in low germination percentages due to insufficient physiological maturity. In this study, the winter wheat cultivar 'Yannong 301' was used to optimize post-harvest treatments for early-harvested seeds. Single-factor experiments showed that 20-25 days after anthesis (DAA) represented a critical window during which germination percentage surged from 34.63% to 64.67% (P< 0.01). The optimal drying temperature was 40 °C in the drying temperature experiment. In the drying duration experiment using seeds harvested at 30 DAA, germination percentage reached 80.00% after 5 d of drying at 40 °C. Additionally, in the moist pre-treatment experiment using seeds harvested at 30 DAA, a 4-d treatment increased germination percentage to 95.94%. Orthogonal experiment further revealed that grain-filling duration after anthesis was the most important factor affecting germination percentage, with 23 days after anthesis (DAA) as the earliest suitable harvest time. The final optimized protocol was: harvest at 23 DAA + drying at 40 °C for 2 d + moist pre-treatment at 4 °C for 2 d + 1% H2O2 soaking for 1 d, achieving 97.06% germination within 35 d from anthesis to the end of the germination test. This protocol represents a practical optimum under the tested conditions. Validation across 10 winter wheat cultivars showed that germination percentages ranged from 80.57% to 95.69%, significantly outperforming untreated controls. The protocol also achieved a line-based seedling emergence rate of 97.5% (195/200) in a single seed descent (SSD) population, indicating its potential to support efficient single-seed descent advancement. This study identified grain-filling duration after anthesis as the key limiting factor for seed germination of winter wheat under SB, and established an efficient post-ripening treatment workflow that achieved high germination percentage and stable performance, providing critical technical support for large-scale breeding population construction and efficient multi-generation cycling.