PENINGKATAN KERAGAMAN Grammatophyllum scriptum (L.) Blume ASAL SULAWESI DENGAN IRADIASI SINAR GAMMA

Grammatophyllum scriptum (L.) Blume or tiger orchid is one of Bogor Botanic Gardens’ collections which was collected from Sulawesi. Elongated stem of this species frequently occurred during in vitro propagation. Therefore, gamma irradiation was used in order to obtain mutation of protocorm. The aim of this study was to reduce the length of segment stem using gamma irradiation in order to generate rosette leaf arrangement as a candidate of superior mutant produced. Four doses of gamma irradiation were used viz. 0 Gy, 15 Gy, 30 Gy, and 45 Gy. Seeds were germinated in various modification media such as, modification of Knudson’C medium (KC and KCA), modification of VW medium, and modification of Hyponex medium. The result showed that VW modification medium gave best media for seeds germination. Subsequently, the protocorms growing in this medium were irradiated to create mutant. Based on data analysis showed that Lethal Dose 50 (LD 50) of protocorm G. scriptum was found in 43.46 Gy and for LD 20 was found in 20.9 Gy. Diverse stem morphology occurred in 15–30 Gy dose irradiation, meanwhile 45 Gy irradiation caused entire protocorms fail to recovery and finally dead.