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Steviol Glycoside Content Dynamics during the Growth Cycle of Stevia rebaudiana Bert

The number of people suffering cardiovascular diseases, diabetes, hypercholesterolemia and obesity has increased globally. For this reason, the demand for non-caloric sweeteners has increased while sugar consumption has decreased. In this context Stevia plays an important role. Besides being a natural sweetener, stevia leaf extracts have other interesting properties, including decreasing blood pressure, improving digestion and gastrointestinal function and protecting against dental caries.

The sweetener compounds in Stevia, steviol glycosides (SG), are mainly found in the leaves. The SG content depends on the plant’s growth stage and is usually highest just before flowering. In temperate areas, Stevia is a polyannual crop (5 - 7 years) with a vegetative period lasting from April-May until October, during which time the crop can be harvested two or three times. This research focused on the need for knowledge about Stevia’s response to temperate climates in Southern Europe.

Two field assays were established from June to October 2013 at two sites in Navarra (Spain). The biomass and content of the two major SG, stevioside (ST) and rebaudioside A (RA) were measured using High Performance Liquid Chromatography (HPLC) in 66 cloned plants at different developmental stages. Scatterplots of dry leaf biomass, leaf-to-stem ratio, ST and RA versus time after planting were performed and a polynomial surface for each site was fitted using local polynomial regression fitting with the loess function from the statistical software R.

The results indicated that leaf biomass increased with time at both sites, but peaked at different dates. The dynamic of ST percentage in leaves throughout plant development differed between the two sites. The dynamic of RA percentage in leaves throughout plant development also differed between the sites.

In conclusion, though the results from the two sites showed different SG leaf content dynamics during the plant growth, the optimum harvest date at both sites coincided with the bud-flowering stage at the beginning of September (around 96 days after planting), when a ST yield of 27 g·m-2 was reached. And the results show that stevia can be successfully cultivated in this region, good glycoside yields are obtained under the long daylight conditions, and there is a long vegetative growth period (from spring to late summer).


Article by Ana Belen Guerrero, et al, from Universidad Pública de Navarra, Campus de Arrosadia, Pamplona, Spain.

Full access: http://mrw.so/4Edr87
Photo credit: M. Martin Vicente on Visualhunt/CC BY.

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