EFFECTS OF ETHYL METHANESULFONATE ON MORPHOLOGICAL AND PHYSIOLOGICAL TRAITS OF PLANTS REGENERATED FROM STEVIA (STEVIA REBAUDIANA BERTONI) CALLI

Abstract

Calli induced from leaf explants cultured on medium containing 0.1 mg/L thidiazuron (TDZ) were exposed to various concentrations of EMS ( 0.1, 0.2, and 0.5%) at different time courses (30, 60, and 120 minutes). The effects of the various concentrations of EMS and different exposure times and the interactions of these factors on the traits of regenerated calli were significant. The number of produced shoots declined with increases in EMS concentrations and in exposure durations. EMS also had significant effects on the morphological and physiological traits of the regenerated plants. Among the 12 studied traits, the M 10 , M 11 , and M 6 mutant lines exhibited the highest variation in terms of morphological and physiological characteristics compared to the control. Among the studied mutants, M 10 had the maximum shoot dry weight, root fresh weight, and chlorophyll a and carotenoid contents up to 102, 30, 358, and 658% higher, respectively compared to those of the control. These mutant lines can be further used for improvement of physiological characteristics as well as for higher quantities and quality of terpene glycosides, such as rebaudioside-A, which does not have a bitter aftertaste.