An efficient mass propagation method for Bletilla. formosana (Hayata) Schltr. was successfully established through direct shoot organogenesis. Multiple shoots were induced from protocorm explants on half strength Murashige and Skoog (1/2-MS) basal medium containing 2 mg/L N-phenyl-N'-1,2,3-thiadiazol-5-yl urea (TDZ) and 0.5 mg/L l-naphthaleneacetic acid (NAA) with the highest shoot formation rate of 100% and a maximum average shoot number of 5.2. The application of either NAA or 2,4-clichlorophenoxy (2,4-D) significantly induced root induction from shoots, and 2 mg/L NAA provided the highest root formation rate of 100% and a maximum number of roots (4.4 per shoot). Supplementation with kinetin and benzylaminopurine (BAP) of 0.5 similar to 2.0 mg/L in 1/2 -MS basal medium significantly promoted plantlet growth. To optimize the in vitro development of plantlets, 1/2-MS basal medium with modified 1/4-strength nitrogen content, and 20 g/L sucrose was used. Well-developed plantlets were successfully acclimatized in a greenhouse with over a 90% survival rate. This effective protocol of in vitro plant regeneration through direct shoot organogenesis can be utilized for the mass propagation and germplasm conservation of B. formosana.
