The effect of different factors on somatic embryogenesis of stevia plant (Stevia rebaudiana Bertoni.)

Stevia plant(Stevia rebaudiana Bertoni.) is an important plant species due to its high content of recoverable natural sweeteners. Considering the industrial and medical importance of plant, the current study was performed with the aim of optimizing somatic embryogenic of this plant. Embryogenic callus induction and embryogenesis were investigated using different concentrations of Benzyl Adenine (BA), Naphthalene Acetic Acid (NAA) and 2,4-Dihydrophenoxy acetic acid (2,4-D) in leaf and bud explants in MS culture medium in a factorial experiment based on completely randomized design (CRD) with five replications. The highest callus induction was obtained in culture media contained 0.01 mg/l (BA + 0.5 mg/l 2, 4-D and the highest embryo induction was obtained in 0.01 mg/l BA + 1 mgl-1 2, 4-D treatment. Also the effect of Casein hydrolysate on the embryogenesis of the Stevia plant were investigated in five concentrations (0, 50, 100, 150 and 200 mgl-1) and coconut milk in two levels (0 and 55 ml) by both explants of leaf and bud in a factorial experiment based on CRD with six replications.  In concentrations of 0 and 50 mg/l of Casein hydrolysate respectively obtained the highest (20.2%) and lowest (7.84%) embryos. The percentages of embryogenesis in MS medium without coconut milk was 78.82% for bud explants and 25.09% for leaf explants, and finally, embryos were transferred to medium containing 0.1 mgl-1 of GA3 for organogenesis, and 18.03% of the embryos were grown to complete seedling.