Micrografting of Protea cynaroides

The inability to induce rooting of in vitro-established Protea cynaroides microshoots has prevented the production of complete plantlets. A successful shoot-tip micrografting technique was developed using in vitro-germinated P. cynaroides seedlings as rootstocks and axenic microshoots established from pot plants as microscions. Thirty-day old seedlings, germinated on growth-regulator-free, half-strength Murashige and Skoog medium, were decapitated and a vertical incision made from the top end. The bottom ends of microshoots established on modified Murashige and Skoog medium were cut into a wedge (‘V’) shape, and placed into the incision. The micrografted explants were cultured in a growth chamber with the temperature adjusted to 25 ± 2°C, with a 12-h photoperiod. Best results were obtained by placing the microscions directly onto the rootstock without any pre-treatments. Dipping the explants in anti-oxidant solution or placing a layer of medium around the graft area led to the blackening of the microscion