Impact of Gamma Irradiation Induced Variation in Cell Growth and Phytoecdysteroid Production in Sesuvium portulacastrum

Abiotic stress in the form of gamma irradiation has been shown a potent inducer of oxidative stress in plant cell cultures which produce higher amounts of commercially important secondary metabolites. In the present study, the impact of low doses of gamma irradiation on growth and accumulation of 20-hydroxyecdysone of Sesuvium portulacastrum was investigated. Shoot cultures were established on Murashige and Skoog medium supplemented with indole-3-acetic acid (0.5 mg L−1) and N 6-benzylaminopurine (2.0 mg L−1). Mutations were induced in tissue culture by treating multiple shoots at low doses of gamma irradiation in the range from 5 to 40 Gy. In vitro cell growth and 20-hydroxyecdysone were assessed during M1T1, M1T2, M1T3, and M1T4 generations. A gamma radiation dose of 20 Gy was calculated as 50% of the lethal value (LD50). The survival rates of multiple shoot cultures exposed to high doses were gradually reduced in the course of increased order of generations. High-gamma irradiation doses were harmful to growth and 20-hydroxyecdysone production. The accumulation of 20-hydroxyecdysone of 0.139 mg/plant dry weight was significantly two-fold higher than non-irradiated shoot cultures. The stressed shoots increased 13-fold 20-hydroxyecdysone at 20 Gy during the M1T4 generation compared to the yield of the M1T1 generation. The ex vitro plants produced 0.321 mg/plant dry weight of 20-hydroxyecdysone which was remarkably greater than the untreated control. The present study postulated that gamma radiation induced metabolic changes and easy-to-achieve putative mutant comprised with the high amount of 20-hydroxyecdysone.