Effect of gamma rays on seed germination, survival rate and morphology of stevia rebaudiana hybrid

Abstract

The effects of gamma radiation are investigated by studying seed germination, survival rate and morphological characteristics of Stevia rebaudiana. Improvement of stevia plant through mutagenesis could be one of the ways to produce stevia with delay flowering. Currently, stevia varieties in Malaysia exhibit early flowering because they received day length less than 13 hours. In this study, seeds of stevia hybrid, H2, are exposed to gamma irradiation doses at 0, 100, 300, 500, 700, 900 and 1100 Gy. Our results show that the germination and survival rate, as well as morphological parameters of stevia decreased by increasing the irradiation dose. Moreover, irradiated seeds exposed to higher doses (>500 Gy) failed to germinate. Based on the survival percentage vs gamma doses, the calculated lethal dose was 323 Gy, which will allow obtaining promising stevia mutants. The plant height and number of leaves in irradiated plant obtained were highest in treatment 100 Gy, 13.50±7.48 cm and 16.00±7.66 respectively. Meanwhile, the length of leaves recorded was highest in treatment 300 Gy (3.00±0.89 cm). Analysis on the chemical content and molecular level of the irradiated plant for future work are useful to verify the changes due to the radiation. Gamma irradiation is a promising alternative to obtain a greater stevia variability for advanced mutant lines.