Abstract
An efficient in vitro propagation method was established for Brasilidium forbesii (Hook.) Campacci using transverse and longitudinal thin cell layer (tTCL and lTCL, respectively) culture systems. Six-month-old protocorms from in vitro germinated seeds were used for this study. TCLs (1.0-mm thick) from protocorms were grown on Woody Plant Medium (WPM) supplemented with benzyladenine (BA) (0.5–4.0 µM).The lTCL technique was more efficient for inducing protocorm-like bodies (PLBs) and regenerating shoots than the tTCL technique. The frequency of PLB formation was influenced by BA concentration, and the lTCL explant grown on a medium containing 2.0 µM BA produced the highest percentage of new protocorms (77%) with a total of 22.7 PLBs per explant, after the first subculture on the same medium. Plantlet development was optimal on WPM medium containing 3.0 g L -1 activated charcoal, and indole-3-butyric acid was not necessary for rooting. Regenerated plants were successfully acclimatized in a greenhouse after 16 weeks using vermiculite as the substrate (100% survival).
Highlights
Brasilidium forbesii (Hook) Campacci is an endemic epiphytic orchid species found in the Atlantic Forest of Brazil
Globular protocormlike bodies (PLBs) and greenish-yellow protuberances were observed on the surface of the thin cell layer (TCL) explants after four weeks in the dark, followed by two weeks of culture in a 16-h photoperiod (Figure 1D), and these protuberances gradually increased in size and developed into shoots by the end of eight- to 12 weeks under a 16-h photoperiod condition (Figure 1E)
Of the two techniques tested, longitudinal thin cell layer (lTCL) was more effective than transverse thin cell layer (tTCL) for PLB formation, and subculturing using the same BA concentration increased the formation frequency and total number of PLBs
Summary
Oncidium forbesii Hook) is an endemic epiphytic orchid species found in the Atlantic Forest of Brazil. Orchids were once considered to be difficult-to-propagate plants in vitro, but thin cell layer (TCL) technology has helped develop methods for their tissue culture, making mass clonal propagation easier and more reproducible (TEIXEIRA DA SILVA, 2013). TCL culture systems are promising and efficient with regard to the total output of orchid plantlets compared to other conventional in vitro methods for rapid regeneration of orchids. These culture systems have not yet been completely exploited for propagating commercially important orchids (HOSSAIN et al, 2013). To obtain rapid plant regeneration with a high frequency, TCL culture methods were exploited for mass propagation of B. forbesii. The effects of benzyladenine (BA) on PLB induction, of indole3-butyric acid (IBA) and activated charcoal on plantlet development, and substrates on acclimatization of TCL explants were evaluated
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