High frequency in vitro  regeneration from embryonic tip of Wucai ( Brassica campestris   L.)

An effective and efficient regeneration system is essential for the successful implementation of plant genetic transformation. Establishing a high-frequency regeneration system requires appropriate explants and a differentiation medium conducive to explant growth. In this study, the efficiency of three regeneration protocols were investigated for multiple shoot induction in Wucai ( Brassica campestris syn. B. rapa L.). Explants including embryonic tip (derived from mature seeds), hypocotyl, and cotyledonary node explants were tested, and various factors were optimized under in vitro conditions. Following optimization using the ‘Huiwu 20’ material, embryonic tips from mature seeds germinated for 60 hours achieved the highest regeneration frequency (87.10%) and produced the maximum number of shoots per explant (8.17). In contrast, cotyledonary node and hypocotyl explants from 4-day-old seedlings displayed lower regeneration frequencies (66.47% and 45.73%, respectively) and fewer shoots per explant (5.07 and 3.23, respectively). Healthy, rooted plantlets were successfully obtained from all types of explants. However, regenerated shoots (approximately 2 cm in height) derived from embryonic tip explants exhibited the most rapiddevelopment, requiring approximately 20 days. These findings highlight the potential of the embryonic tip regeneration system for an efficient and reproducible method for in vitro shoot regeneration, providing a foundation for genetic transformation in Wucai.