Elicitor induced stevioside production, in vitro shoot growth, and biomass accumulation in micropropagated Stevia rebaudiana
Akgun, Ismail Hakki
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For the purpose of enhancing the secondary metabolite content in micropropagated Stevia rebaudiana plants without inhibiting plant growth, node explants were cultured on woody plant medium (WPM) containing alginate (ALG), casein hydrolysate (CH), pectin (PEC), yeast extract (YE), methyl jasmonate (MeJA), salicylic acid (SA), or chitosan (CHI). The highest shoot number; shoot length, node number, and leaf number; leaf length; and stem diameter were observed on WPM containing 1.0 g/L YE; 100 A mu M CHI; 0.5 g/L CH; and 1.0 g/L ALG, respectively. The root regeneration frequency reached 100 % on WPM supplemented with 0.5, 1.0, or 2.0 g/L PEC, 1.0 g/L YE, or 50 A mu M CHI and the control. The highest root number was obtained on WPM containing 0.5 g/L PEC, while the longest root length was observed on WPM containing 1.0 g/L YE. The highest biomass accumulation was observed with treatment of 100 A mu M CHI. According to the high-performance liquid chromatography results, except for the treatments with 200 A mu M CHI, 100 or 200 A mu M MeJA, and 200 A mu M SA, the remaining elicitor treatments increased stevioside production compared to the control. The production of stevioside increased from 1.56 mg/g dry weight (DW) to 14.69 and 14.54 mg/g DW in the in vitro plantlets exposed to 0.5 g/L ALG and 2.0 g/L YE, respectively. Rebaudioside A was observed on only 0.5 g/L ALG-treated plants as 0.55 mg/g DW. The stevioside content of field-grown plants was identified as 15.06 mg/g DW. The present findings provide important information regarding the effect of elicitors on plant growth and secondary metabolite production of in vitro micropropagated S. rebaudiana.