Radiosensitivitas dan Pertumbuhan In Vitro Protocorm Anggrek ‘Tien Soeharto’ (Cymbidium hartinahianum J.B. Comber & R.E. Nasution)
C. hartinahianum J.B. Comber & R.E. Nasution is an endemic orchid in North Sumatra. The habitat of C. hartinahianum is restricted in highland with low temperature. Most of its natural habitat has been shifted to other land use. Induced mutation using gamma-ray irradiation is an alternative method to obtain the orchid mutant with better vigor and tolerance to higher temperatures. This study aimed to evaluate C. hartinahianum protocorm’s radiosensitivity to gamma irradiation and evaluate irradiated protocorm growth in two different temperature culture rooms. The protocorms were exposed to 0, 5, 10, 15, and 20 Gy of gamma irradiation. A half number of irradiated protocorm were incubated at 16-18 oC and a half another at 22-27 oC culture room temperature to evaluate their radiosensitivity and growth. The result showed that the LD20 and LD50 of protocorm cultured in 16-18 oC were 26.98 Gy and 38.24, while the LD20 and LD50 of protocorm cultured in 22-27 oC were at 17.08 Gy and 27.29 Gy. Protocorm-like bodies (PLBs) proliferation and shoot morphogenesis were better in the tissue culture room at 22-27oC. This experiment suggested that the re-irradiation of PLBS could be performed at the LD20 or LD50 at 22-27 oC culture room (17.08 Gy and 27.29 Gy) to find a putative mutant of C. hartinahianum.
Keywords: gamma rays irradiation, in vitro mutation induction, multiplication, lethal-dose, protocorm like bodies (PLBs)