THE ROLE OF NEW SYNTHETIC CYTOKININS IN THE IMPROVEMENT OF MASS PROPAGATION OF PHALAENOPSIS VIA PROTOCORMS REGENERATION

Most of the commercially cultivated Phalaenopsis (pot plant and cut flower) are produced from seeds; the multiplication rate is very high but the produced plants are heterogeneous, unstable and the variability in phenotypes, plant growth and flowering delay is very important; it is then very difficult to establish a profitable industrial propagation program. In order to resolve the problems connected to the sexual reproduction, several techniques have been developed for the in vitro vegetative propagation of Phalaenopsis; this includes meristem culture (Intuwong and Sagawa, 1974), leaf tissue culture (Tanaka et al., 1975), root tips (Tanaka et al., 1976), culture of flower stalk buds (Arditti et al., 1977), internodal segments of flower stalks (Lin, 1986), shoot tips of flower stalk buds (Ichihashi, 1992). Unfortunately any of these techniques can be applied to a commercial system of micropropagation because of the too low multiplication rate and mother plant destruction.

This paper presents a vegetative micropropagation method to produce Phalaenopsis on a commercial scale through the somatic embryogenesis procedure.

In the present study we describe a practical somatic embryogenesis method, through protocorms of regeneration, to mass propagate the Phalaenopsis. We also determined the optimal culture conditions to regenerate plants.

We examined various factors that affect the initiation, the multiplication and the evolution of protocorms; some of the most important factors for the formation of protocorms are the choice of the explant, the growth regulators and their concentration and the basal culture medium.

Internodal flower stalk segments with an axillary bud were removed from the mother plant cultured in greenhouse. The nodal-cuttings were disinfected, rinsed with sterile water and cultured on the Vacin-Went medium (V-W; Vacin and Went, 1949) modified and supplemented with -naphthaleneacetic acid (NAA) and 6-benzylaminopurine (BAP) with NAA/BAP<1 (V-W_m: cuttings medium).

After 1 to 3 months of culture, the axillary buds developed into flower stalks or vegetative shoots depending of their position on the flower stalk.

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