Establishment of highly efficient plant regeneration of Paeonia ostii ‘Fengdan’ through optimization of callus, adventitious shoot, and rooting induction

Tree peony is a famous ornamental plant, while the low propagation rate is the main hurdles hindering the industry development. Till now, the highly efficient regeneration system for tree peony is not established. In this study, using Paeonia ostii ‘Fengdan’ mature embryos, the effects of variations in inoculation method, initiating culture, adventitious shoot induction, rooting media, plant growth regulators (PGRs), and a non-conventional PGR (plant extracts) on regeneration from explants were evaluated. In embryo cultures, embryonic callus induction rate of 1/4 embryos was the highest among those of embryos with other three technical treatments (whole embryos, 1/2 embryos, and pieces of embryos). The woody plant medium (WPM) containing 1.0 mg • L − 1 6-BA, 0.5 mg • L − 1 GA3, 30.0 g • L − 1 sucrose, and 3.0 g • L − 1 phytagel significantly improved shoot induction and multiplication. 3.0 mg • L − 1 plant extracts promoted hypocotyl germination, rooting, and root growth, in direct embryo culture, and a combination of 3.0 mg • L − 1 plant extracts + 2.0 mg • L − 1 IBA + 1.5 mg • L − 1 IAA produced optimal rooting induction rate for multiple shoots in direct embryo culture and indirect somatic embryogenesis. For the three in vitro micropropagation methods, the highest shoot proliferation coefficient (5.4 ± 0.2) was obtained with indirect somatic embryogenesis. Fortunately, the propagation ability of shoots remains high, even when culture propagation was continued for more than two years. Thus, a reliable system for plant regeneration from mature embryos derived from P. ostii ‘Fengdan’ callus and two direct embryo culture systems have been established. The novel regeneration system could facilitate uniform seedling production.