Effects of Acute Gamma Irradiation on the Morphology of Stevia rebaudiana

Stevia is a short-day plant with constant day length less than 12 hours in Malaysia cause to generate flower early. The shorter vegetative period, resulting in low content of steviol glycosides compound. Cultivation of stevia in Malaysia is a challenge due to lack of suitable variety. The response to gamma irradiation varies among plant species and affected by the irradiation dose. The method applied was acute gamma irradiation with six doses (50, 100, 250, 300, 400 and 500 Gy) to investigate the effect of radiation. The LD50 value was at 182 Gy. The number of days for seed to germinate was varied in all treatments and none of the seedlings survived at 400 Gy and 500 Gy of irradiation. The plant height recorded the highest in treatment 50 Gy (142.0±1.98). Meanwhile, for other parameters such as the number of leaves, the number of branches, leaf width and leaf length were decreased as the dose increases. Overall, our findings suggest that low doses of radiation (below 325 Gy) is the suitable dose to study the improvement of stevia by acute gamma irradiation.