CLONAL PROPAGATION OF PELARGONIUM X HORTORUM THROUGH TISSUE-CULTURE - EFFECTS OF SALT DILUTION AND GROWTH-REGULATOR CONCENTRATION

Different culture media were compared at the initiation and multiplication steps to develop a rapid production system for geranium (Pelargonium x hortorum) in vitro. Different salt dilutions of the Murashige and Skoog (MS) (1962) mineral medium were used in combination with different concentrations of 1-naphthaleneacetic acid (NAA) and 6-benzyladenine (BA) in order to optimize initiation of shoots of four geranium cultivars. The use of a MS basal medium with half-strength macrosalts supplemented with 0.11 muM NAA and 0.89 muM BA gave the best results in initiation. More than 40% of the apices initiated on this medium produced multiple shoots within a month. Subsequently, the effect of different concentrations of growth regulators was quantified by the mean of ''shoot doubling time'' evaluation. The shortest time recorded was 10.5 d for a theoretical production of 1 x 10(9) plantlets/apex/year. This is the first quantitative evaluation of geranium production in vitro. Geranium plantlets rooted easily on a half-strength MS medium without growth regulators. Acclimatization of geranium plantlets was characterized by high survival rates (94%) and the plants thus produced were phenotypically comparable to seed-derived plants.