Effects of Ethyl Methane Sulfonate on Some Phytochemical Traits, Stevioside and Rebaudiosid a Contents of Stevia (Stevia rebaudiana Bertoni) Plants Regenerated from Calli

In order to evaluate ethyl methane sulfonat (EMS) mutagenic substance on some of the phytochemical traits of stevia plants regenerated from calluses, two separate experiments were conducted with three replications. At the first experiment a factorial arrangement based on completely randomized design was used. leaf explants were transferred to MS culture media containing the growth regulator thidiazuron (TDZ) at 0.1 mg/L, and callus masses were exposed to various concentrations of EMS (0.1, 0.2 and 0.5%) for different periods (30, 60, and 120 minutes). Then, callus masses were subcultured in MS culture media. Based on the findings of the first experiment, the effects of the various concentrations of EMS, different exposure durations and the interaction effects of these factors were significant on the traits of regenerated calluses. The number of produced stems declined when EMS concentrations and exposure durations were increased. In the second experiment, completely randomized design, each plant regenerated from calli which treated with EMS was considered as a mutational event and a colony population with members of similar age was prepared for each unique plant. In each treatment, the regenerated plants with suitable growth forms were selected, and each individual seedling regenerated from callus was assigned a unique code. After two months, some phytochemical traits and the amount of glycoside sugars (stevioside and rebaudioside A) were measured. Results of ANOVA showed that EMS had significant effects on phytochemical traits and the amount of glycoside sugars at the 1% level. Among the studied mutant samples, the M6, M10, M11, M18 and M19 showed the most changes of most traits as compared to the control sample. Also, M8 mutant had the maximum steviosid and rebaudiosid A contents (.3 and .3% more than control, respectively).