Controlling phytoplasma-causing disease through combination of tissue culture
technique and radiation treatment represented a short method for high level
management. To investigate the effect of gamma rays to produce healthy plantlets, the
hibiscus witches' broom phytoplasma was transmitted by grafting into healthy
hibiscus plants, the in vitro-infected hibiscus explants were exposed to gamma
radiation at different doses - 5 gray (Gy), 10Gy, 15Gy, 20Gy and 25 Gy- emitted
from cobalt 60 (60Co) for 30 minute. All applied doses resulted in phytoplasma-free
hibiscus plantlets with different survival activity. The presence of phytoplasma 16Sr
DNA was examined using PCR detection before and after treatments. The different
treatments of radiation resulted in different survival rates and phytotoxic effects
including leaf yellowing and lack of growth. The 5Gy dose was proved to be best
effective dose for controlling the phytoplasma without affecting the in vitro growth
and survival rate, while the higher doses leaded to strongly reducing the survived
hibiscus explants with increasing the inability to re-shoot.