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Stevia is a plant attracting attention due to its capability to synthesize a group of chemical compounds with sweet taste, i.e. steviol glycosides. Steviol glycosides are successfully applied as a natural sweetener, and some of them have also therapeutic properties. This paper presents available information on the use of stevia plant tissue cultures with the focus on their potential application in food industry. Detailed analysis was done concerning the research employing in vitro culture techniques and the use of them in biosynthesis of secondary metabolites of high importance for the food industry. Both established achievements and most recent publications on stevia were used for assessment of practical applications of the aforementioned techniques and prospects for their development.
In the preceding research, stevia has been typically cloned in vitro using two media, on which the shoots were formed (3–6 weeks), and on the other they were rooted (3–5 weeks). This study aimed at finding the possibility for rapid stevia propagation from large nodal explants using the MS basal medium [Murashige and Skoog 1962], with low auxin concentrations (0.5, 1 and 2 mg.dm–3). The plants were obtained as soon as after three weeks. The best results were obtained from media with various concentrations of the indole-3-acetic acid (IAA) and the highest concentration of phenylacetic acid (PAA). Plants were formed by 83.9–86.0% of explants, they had high weight (234–253 mg), two shoots measuring 2.07–2.37 cm and 5.8–8.3 roots measuring 1.00–1.24 cm. Mean plant weight was the lowest on media with indole-3-butyric acid (IBA) (185–192 mg). Both explant buds formed single shoots, but their development was typically uneven. The differences in the length and weight of shoots were the lowest on media with IAA and at lower PAA concentrations. Plants from the media with IAA and the control medium were distinguished by higher number of nodes. The percentage share of shoots in the total plant weight was the highest on media with PAA (62.1–62.7%), and the lowest at higher concentrations of α-naphthaleneacetic acid (NAA) (47.9 and 48.9%). Parts of explants immersed in media developed callus, and the highest amounts of this tissue were found in the media with NAA. 92.3% of plants survived the acclimatization. The applied procedure may be used for rapid in vitro cloning of selected stevia genotypes. The use of one medium enables reduction of seedling production costs. Moreover, cyclical cloning and extending the production scale is possible.
Today, more and more increasing interest in low-calorie sugar substitutes. The food industry uses synthetic sweeteners such as saccharin, aspartame, sucralose, however, greater emphasis is placed on natural sweeteners. An example of such a substance can be steviol glycosides extracted from the stevia, derived subtropical and tropical regions of North and South America. The content of sweet on stevia is varied and depends on the method of propagation and cultivation. Dry leaves of stevia is 30 times sweeter than sugar, however, isolated from one steviol glycosides 300 times.
There has been a growing interest over the last years in techniques using alternative and pharmaceutical plants due to their wide potential applications. These species are characterised by valuable and multidirectional usable features, due to which their practical application is superior to their physiognomic features. These plants may provide a raw material for production of medicines, cosmetics or may be used for animal feeds. Moreover they may be used as ornamental, melliferous and energy plants. Owing to their generally low soil requirements they are used in the reclamation of degraded land. Among the species characterized by multidirectional use are Silphium perfoliatum, Helichrysum arenarium and Stevia rebaudiana. These plants are characterized by a high content of active compounds and a number of pro-health characteristics. Because raw materials for production of medicines and cosmetics should be standardized, cultures maintained under controlled conditions are a good source of seedlings.
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