Abstract
Tree peony (Paeonia sect. Moutan) is an economically important multipurpose woody plant in terms of its medical, ornamental and oil values, but its breeding and industrial development are severely limited due to inefficient traditional propagation methods and existing in vitro regeneration systems. Meristematic nodules (MNs) are an attractive alternative to solve this problem. This study first presented a protocol for in vitro regeneration of P. ostii ‘Feng Dan’ via MN culture with four consecutive steps, including embryogenic callus (EC) formation, MN induction and leaf cluster differentiation, shoot elongation, rooting and acclimatization. The highest EC induction rate (81.25%) was achieved when cotyledons were cultured on modified Murashige and Skoog (mMS) medium with 4.04 µM N-(2-chloro-4-pyridyl)-N-phenylurea (CPPU) + 5.37 µM α-naphthylacetic acid (NAA) for 30 days. The optimal MN induction rate (100%) and leaf cluster differentiation rate (45.83%) were obtained when ECs were cultured on modified woody plant medium (mWPM) supplemented with 2.02 µM CPPU + 2.27 µM thidiazuron (TDZ) for a subculture time of 10 days. The combination of 1.29 µM 6-benzyladenine (BA) + 0.58 µM gibberellin (GA3) yielded the best shoot elongation (13.40 shoots per nodule), rooting rate (43.33%) and consequently survival rate (45.83%). The study will be beneficial to the mass propagation, breeding and genetic improvement of tree peony.
Highlights
The Meristematic nodules (MNs) was initiated indirectly form calli derived from cotyledons of P. ostii ‘Feng Dan’, which was consistent with previous descriptions in P. lemoinei ‘Golden Era’ (Qin et al 2012) and P. rockii
Our results revealed that not all the nodules were able to induce shoots, the best efficiency of MNs induction and subsequent differentiation required different plant growth regulators (PGRs) combinations according to variance analysis
An efficient in vitro regenerative system was developed for the first time via MN culture in P. ostii ‘Feng Dan’
Summary
P. ostii is main option for oil tree peony because of the high yield and adaptability. The low efficiency and long cycle of conventional propagation methods, such as grafting and division, severely constrain its breeding and are insufficient to address the increasing commercial demands. An efficient and stable in vitro regeneration system is urgently needed. No regeneration system published to date can meet the needs for the propagation and genetic manipulation of tree peonies due to various obstacles, such as vitrification, low multiplication, poor rooting and difficult acclimatization in micropropagation (Beruto et al 2004; Wen et al 2020), rare differentiation in callus culture (Zhu et al 2018), and high deformity rates and low germination in somatic embryogenesis (Du et al 2020a, b); innovative breakthroughs are needed to overcome this problem
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