Establishment of a complete in vitro micropropagation and plant regeneration system for Paeonia suffruticosa ‘Hongxialanman’ by inducing dormancy-like bud formation

Tree peony (Paeonia sect. Moutan) is an economically important woody crop that is difficult to propagate. At present, tissue culture is not used for industrial-scale propagation and breeding of tree peony because of its low survival rate after transplantation and underdeveloped regeneration system. The present study established a complete micropropagation and plant regeneration system for tree peony by inducing dormancy-like bud formation. Axillary buds and petioles were used as explants. The highest shoot proliferation coefficient (3.5 shoots/explant) was obtained on solid Murashige and Skoog (MS) medium (double-strength Ca²⁺) containing 1.5 mg/L 6-benzylaminopurine (6-BA), 0.05 mg/L 1-naphthaleneacetic acid (NAA), and 150 mL/L coconut water. The maximum rates of callus induction (94.4 %) and adventitious bud regeneration (63.2 %) from petiole explants were on solid MS medium containing 1.0 mg/L thidiazuron (TDZ), 0.1 mg/L NAA, 150 mL/L coconut water. The highest rate of adventitious root induction (92.5 %)‌ was obtained after culturing shoots in the dark for 7 days‌ on solid ‌½ MS medium (double-strength Ca²⁺)‌ containing ‌3.0 mg/L indole-3-butyric acid‌ (IBA), ‌0.5 mg/L NAA‌, and ‌0.5 g/L triacontanol (TA). Rooted plantlets formed dormancy-like buds when cultured on ½ MS medium‌. The survival rate after transplanting reached 92.8 % when the plantlets were transplanted into substrate containing a composite microbial inoculant (CMI). This study not only marks the first complete in vitro micropropagation and plant regeneration system for tree peony, but also provides crucial technical support for industrial-scale seedling propagation and modern breeding.