Evaluation Of The Sensitivity To Ionising Gamma-Radiation Of A Cymbidium Hybrid

Gamma-rays are an important mutagenic agent that can induce new, useful genetic variations in plants. However, gamma-irradiation can also cause damage that negatively affects the use of such mutagens in plant breeding. The aim of the present study was to investigate the effects and damage caused by gamma-radiation in a Cymbidium hybrid, RB001. The relative growth rate of protocorm-like bodies (PLBs) was reduced by 50% at a gamma-ray dose of approximately 40 Gy. Malondialdehyde concentrations increased significantly with increasing radiation dose. However, almost no difference was observed between untreated control PLBs and PLBs treated with 200 Gy 8 weeks after gamma-irradiation. The activities of several antioxidant defence enzymes increased gradually with increasing theta-ray dose, 24 h after irradiation. These enzymes showed different responses between 1 and 4 weeks, but no difference 8 weeks after irradiation. The 'comet assay' and flow cytometry were performed. Clear differences in radiation-induced damage were observed between control and 200 Gy-treated PLBs at 24 h. However, PLBs had a tendency to recover from 4 weeks after irradiation, and the integrity of their DNA was similar in samples treated with 10-200 Gy. These results indicated that gamma-rays caused little DNA damage and the plants could recover. This demonstrated the feasibility of using physiological responses, the 'comet assay', and flow cytometry to detect DNA damage after gamma-irradiation.