Direct shoot regeneration from nodes of Phalaenopsis orchids

Abstract

Nodes with dormant buds from flower stalks of orchid Phalaenopsis sp. were plated on six culture media. The composition of the culture media affected the induction, regeneration, number and form of Phalaenopsis regenerants. We managed to obtain direct shoot regeneration without callus formation on all media except for medium F. Medium A, supplemented with 2 mg/l of 6-benzylaminopurine (BAP) and 0.5 mg/l of a–naphtalenacetic acid (NAA) was found to be the most appropriate of all the media used for rapid micropropagation of a large number of vegetative shoots (multiplication factor 8.35 per node) without roots 160 days after inoculation. We found medium B, supplemented with 4.41 mg/l BAP and 1 mg/l NAA less appropriate for vegetative shoot production (multiplication factor 2.08 per node) also because the regenerants ceased to elongate. Medium C, containing BAP (2 mg/l) and a lower nitrogen content showed the highest multiplication rate (0.54 per node) for generative regenerants formation. Vegetative regenerants with a generative shoot also formed. This type of regenerant could be of major commercial interest, since period until flowering would be much shortened. Dormant bud induction was poor on medium E (23% regeneration rate) and there was no regeneration on medium F. Regenerants with well-developed roots on medium D (no hormones) most resembled the adult plants, but the vegetative multiplication rate was lower (1.18 per node). Most vegetative regenerants were ready for acclimatization after 90 days of subcultivation on medium D, which also proved to be a successful subcultivation medium for regenerants formed on media A, B and C.