Objective  Seed sterilization and rooting culture are important steps in plant tissue culture. At present, there is considerable variation in the concentration of sodium hypochlorite (NaClO) and seed sterilization time of Brassica napus, as well as the type and concentration of hormone in the rooting media. The purpose of this study was to optimize the method of seed sterilization with NaClO and the formula of rooting medium for B. napus regeneration.

  Method  The optimum concentration of NaClO for seed sterilization was screened by comparing the growth status (such as germination rate, healthy shoot rate and rate of colonies) of seeds treated with different concentrations (0.1%–30.0%) of NaClO, and the appropriate sterilization time was optimized based on the growth status of seeds treated with the optimal concentration of NaClO for 10—30 min. Moreover, the optimum formula of rooting media was screened by comparing the rooting regeneration of seedlings in the media containing 0.1–2.0 mg·L⁻¹ naphthylacetic acid (NAA) / indolebutyric acid (IBA).

  Result  The optimum concentration of NaClO for seed sterilization was 2.0% or 3.0%, and the best time for seed sterilization with 3.0% NaClO was 15 min, causing the 97.4% of germination rate and 85.9% of healthy shoot rate with least rate of colonies. Moreover, this method of seed sterilization is applicable to other 9 plants, especially for B. napus, B. pekinensis and Arabidopsis thaliana. The root regenerated best in the rooting medium containing 0.1 mg·L⁻¹ NAA, in which 92.5% of root regenerated from the cutting point on the 7^th day with the most lateral roots.

  Conclusion  This study optimized the method of seed sterilization and the formula of rooting medium, which laid a foundation for efficient plant tissue culture of B. napus.