Stevia rebaudiana: a study in the volatiles profile from plants grown in the field in the greenhouse and micropropagated in vitro
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abstract
Stevia rebaudiana Bertoni leaves are natural sources of steviol glycosides, which are used commercially for
sweetening and flavouring foods and beverages. Steviol glycosides are natural sweeteners constituting an
alternative to synthetic compounds like cyclamates or aspartame. S. rebaudiana has been produced mainly for
its stevioside compounds but it contains other metabolites with potential therapeutic benefits such as alkaloids,
hydroxycinnamic acids, oligosaccharides or essential oils. The chemical profile of samples development by
micropropagation or in green house or in field conditions, should be characterized to ensure the quality of
the samples supplied by Stevia producers. Multiplication rate and fresh weight were determined for plants
micropropagated in two different culture media (medium A - Murashige and Skoog (MS) without hormones
and sucrose), (medium B - MS with 0.5 mg.L-1 of kinetin and 20 g.L-1of sucrose). Apart from spontaneous
rooting rate determination, induction of plant rooting by auxin shock, using indole-3-butyric acid (IBA) (2
mg.mL-1), was also evaluated. Acclimatization in greenhouse was performed with hydro atomization nozzles
working every 10 minutes. Plants on the field were fertilized by a nutrient solution with N, P2O5, K2O and
B. The essential oil yield was determined for plants in all conditions (in vitro, greenhouse, field) using a
Clevenger-type apparatus. Volatiles were isolated using a Likens-Nickerson apparatus and analyzed by GCMS.
The in vitro multiplication rate was 300% per month and the fresh weight after a 4 week subculture was
0.9 g. Spontaneous rooting rate was less than 4% after 4 months but induced rooting achieved 30% of plants
with developed root system after 1 week and 70% after 2 weeks. Acclimatization rate was 100% after 2 weeks.
The essential oil yield was <0.06% for all samples. Volatiles identification revealed identical composition in all
samples, with α-pinene (11-31%), bicyclogermacrene (5‑19%), trans-β-farnesene (7-15%), β-elemene (6-10%)
and β-caryophyllene (3-10%) as major compounds. Quantitative differences were noteworthy.
