EFFECT OF AUXIN-CYTOKININ INTERACTION AND LIGHT CONDITIONS ON ORGANOGENESIS IN MATURE LEAF EXPLANTS OF PELARGONIUM RAPACEUM (L.) L¿HÉRIT

Pelargonium rapaceum (L.) L’Herit. belongs to the family Geraniaceae, and is classified in section Hoarea within the genus Pelargonium. In general, it propagates through seed and tuber division which produces a small number of stock plants. Alternative technology can be used for mass in vitro propagation which has the potential to benefit from large scale propagation of pathogen indexed plants including rapid multiplication. The objectives of this work were to create efficient plant regeneration procedures in P. rapaceum using mature leaf explants. Leaves were cultured on MS medium supplemented with different concentrations of auxin at 0, 0.1, 1 and 5 mg/L of NAA or IAA used in combination with cytokinin at 0, 0.1, 1 and 5 mg/L of BAP or TDZ. Explants were cultivated under a white fluorescent lamp for 16 h (20-30 µmol/s/m2) or dark conditions in a culture room at 24°C. Significant differences were observed in shoot organogenesis under the different concentrations of growth regulator and culture conditions. Morphogenesis occurred in response to the growth regulator combinations tested. The initial growth occurred after 1 to 2 weeks of culture. The 100% regeneration was found for explants cultured on medium supplemented with a combination of NAA with BAP, and IAA with TDZ. No shoot was observed in any medium containing TDZ. Shoots occurred with explants cultivated on MS medium containing NAA in combination with BAP, and IAA in combination with BAP. Light incubation was needed for explants cultivated on medium using combinations of IAA while the cultures on medium using combinations of NAA resulted in shoot regeneration under both culture conditions. However, the highest number of shoots was obtained from explants cultivated under darkness. Percentage of shoot regeneration and the number of shoots per explant were also observed and discussed.