A modified technique for in vitro propagation of papaya (Carica papaya L.)

Carica papaya L. is an important crop in many subtropical and tropical countries. Many problem areas still exist with the commercial in vitro propagation of papaya. These include leaf senescence, stunted plants produced as a result of cytokinin toxicity, reduced rooting ability and poor root quality. A technique using activated charcoal at 3 g l(-1) as an intermediary culture step before rooting, improved the overall condition and maturity of the microplants thus reducing the cytokinin-toxicity effects resulting from long term use of this phytohormone. Rooting was achieved by soaking the bases of the plantlets in a 5 mg l(-1) IBA solution for one hour and transferring them to a sucrose-free vermiculite medium. This method improved on a double inoculation method previously used where plants were inoculated into an IBA containing medium and then transferred to an IBA-free medium three days later. To reduce ethylene buildup within flasks, the lids were modified to contain small openings plugged with cotton wool. These were removed during initial acclimatisation before transfer to the greenhouse.