An Assessment of Plant Growth Regulators on Asymbiotic Cevelopment and Germination of Immature Embryos of Beclardia macrostachya (Orchidaceae)

Beclardia macrostachya is one of the rarest orchids in Mauritius. In vitro techniques are being used for mass propagation of this orchid for subsequent restoration programs. Successful asymbiotic germination of Beclardia macrostachya was obtained through embryo rescue under in vitro conditions. Modified half MS medium supplemented with 10% coconut milk was used as basal culture medium and the effect of plant growth regulators at different concentrations on embryo development was assessed through qualitative and quantitative parameters. Diameter of embryos, length of protocorm-like bodies (PLBs) and length of developing shoots were calculated using digital photography. Maximal growth was obtained in treatments without any plant growth regulators and with 0.5 mg/L N6-Benzylaminopurine (BAP). Higher levels of Thidiazuron/TDZ (0.3 mg/L) and BAP (1.0 mg/L) though they stimulated embryo development faster, yielded higher level of necrosis later. The results also suggest that plant growth regulator treatments that stimulate fastest embryo development from immature embryos/ovules need not be reliable for further development to PLB and plantlet regeneration.