Micropropagation of Corymbia ptychocarpa

Corymbia ptychocarpa (F. Muell.) K.D. Hill & L.A.S. Johnson (swamp bloodwood), a member of Myrtaceae, is native to northwestern Australia. Swamp bloodwood was introduced into China for ornamental landscape use because of its unique leaves and beautiful terminal inflorescences. An efficient micropropagation protocol is needed for the mass propagation of swamp bloodwood. Disinfested shoot tips with one axillary bud (1–1.5 cm) were cultured on modified Murashige and Skoog (mMS) medium containing with 0.2, 0.3, 0.4, 0.5, or 0.6 mg·L^-1 6-Benzylaminopurine (BAP) and 0.1 or 0.2 mg·L^-1 1-Naphthaleneacetic acid (NAA). Thirty days after culture, the highest induction rate, 93.3%, was observed on the mMS medium plus 0.5 mg·L^-1 BAP and 0.1 mg·L^-1 NAA. The induced shoots were cultured on mMS medium supplemented with 1, 1.5, or 2 mg·L^-1 BAP and 0.1 or 0.2 mg·L^-1 NAA. A total of 5.2 shoots per explant were induced on mMS medium plus 1.5 mg·L^-1 BAP and 0.2 mg·L^-1 NAA. Shoots (~2 cm) were subcultured on ½ strength mMS medium containing 1.0, 1.5, or 2.0 mg·L^-1 Indole-3-butytric acid (IBA) or 0.1 mg·L^-1 NAA to form roots. The highest induction rate, 96.3%, was observed on the ½ strength mMS medium with 1.5 mg·L^-1 IBA. The rooted plantlets were then acclimatized and transplanted into a mix of coconut chaff and red soil (3:1, v/v), and the final survival rate was 81.2%. This micropropagation procedure would be suitable for commercial production of swamp bloodwood.