Gamma Irradiation Effect on the Callus Growth and Shoot Regeneration of Pogostemon cablin Benth.

Abstract. Patchouli is an essential producer of patchouli oil in the perfume industry, and its production needs to be increased to meet market demand. In vitro mutagenesis using gamma irradiation has the potential to produce superior patchouli plants. This study aimed to evaluate the effect of gamma irradiation on callus growth and shoot formation on patchouli callus. Calli were gamma-irradiated at doses of 0, 15, 30, 45, 60, and 75 Gy, then cultured on Murashige and Skoog (MS) medium with the addition of 0.1 mg.L-1 NAA and 0.3 mg.L-1 BA for four weeks. The results showed that gamma irradiation inhibited callus growth and shoot formation. Gamma irradiation increased the percentage of explant browning and decreased explant survival, explant formation of shoots, the total number of shoots, number of shoots/explants, fresh weight of callus and shoots, growth index, and growth rate. The higher the dose of gamma irradiation, the smaller the percentage of explant survival and the lower the ability to form shoots with an average number of shoots formed less. The percentage of explants that survived on callus without irradiation and at a low dose of 15 Gy reached 100%, with an average number of shoots formed between 4.34-5.63 shoots/explant. Meanwhile, the percentage of explants that survived at high doses of 60-75 Gy was 76-82%, with an average number of shoots formed about two shoots/explant. The lethal dose (LD20) for explant survival was 67.98 Gy.