Callus induction and plant regeneration from leaves of peony

Tree peony (Paeonia suffruticosa Andr.) is a valued ornamental plant. This study reports on peony callus induction, shoot organogenesis and plant regeneration using young peony leaves as explants. Various media containing diverse plant growth regulators were assessed for their potency in peony propagation. After exposure of dark-adapted leaf discs to 30 mu mol m(-2) s(-1) of light, inoculation in Murashige and Skoog (MS) + 0.2 mg L-1 2,4-dichlorophenoxyacetic acid (2,4-D) + 0.2 mg L-1 a-naphthaleneacetic acid (NAA) + 3.0 mg L-1 thidiazuron (TDZ) medium resulted to the highest callus induction rate with values reaching up to 87.8%. We identified that MS + 0.2 mg L-1 NAA + 2.0 mg L-1 6-benzyladenine (6-BA) + 2.0 mg L-1 kinetin (KT), with a multiplication coefficient of 3.025, to be the optimal medium for further callus proliferation under light. Inoculation in MS + 2.0 mg L(-1)6-BA + 0.2 mg L-1 NAA + 0.3 mg L-1 TDZ medium allowed 22.22% of callus cultures to differentiate into adventitious shoots, whereas a similar rate of root formation was detected when 1/2 MS + 0.1 mg L-1 NAA + 0.05 mg L-1 IBA + 30 g L-1 sucrose medium was used. Our findings provide important information on peony regeneration and present a new method for peony tissue culture that will potentially facilitate mass propagation and genetic engineering of peony plants.