Efficient in vitro Plant Regeneration from Protocorm of Bletilla formosana (Hayata) Schltr

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 1-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-dichlorophenoxy (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 0.5~2.0 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.