Fast direct regeneration of plants from nodal explants of Stevia rebaudiana Bert.

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.