Background: Stevia (Stevia rebaudiana), a sweet herb and anti-diabetic medicinal plant, could be replaced by artificial sweeteners and even table sugar. It grows in South America. Methods and findings: Somatic embryogenesis of leaf and bud explants was studied in two experiments in a completely randomized design with 5 replications. At first experiment, different concentrations of 6-benzyladenine (BA), α-naphthaleneacetic acid (NAA) and 2,4-Dichlorophenoxyacetic acid (2,4- D) on Murashige and Skoog (MS) culture medium were tested. According to the results the highest percentage of embryogenesis callus obtained in T2 (MS medium supplemented with 1 mg/l BA+2 mg/l NAA) and T6 (0.01 mg/l BA+1 mg/l 2,4-D) (10.87%) and the lowest one (1.25%) observed in T11 (0.5 mg/l NAA+0.5 mg/l 2,4-D). As well as the highest embryogenesis percentage was obtained in MS medium supplemented with 0.01 mg/l BA and 1 mg/l 2,4-D. In second experiment, the effect of casein hydrolyzate in 5 concentrations (0, 50, 100, 150 and 200 mg/l) and coconut milk in two levels (0 and 55 mL) on stevia embryogenesis was investigated. According to the result 78.82% of bud and 25.09% of leaf explants were induced embryo in MS medium. Coconut milk and casein hydrolysate did not show significant difference on callus induction. Resulted embryos were transferred to MS medium containing 0.1 mg/l GA3 for organogenesis, and some of the embryos were grown to complete plant. Conclusion: In this study the most embryo induction was obtained by using MS medium without casein hydrolysate and the lowest one obtained by 50 mg/l casein hydrolysate. It proposed that type and concentration of different PGRs for embryogenic callus induction and somatic embryogenesis of Stevia investigated.
Maryam Dehestani-Ardakani, Kazem Kamali, Soghra Rezaie