An experiment was conducted on in vitro culture of Stevia rebaudiana Bert, an important non-caloric sweetening herb to explore its potential for micro-propagation. Leaf, nodal and inter-nodal segments of the selected herb as explant were cultured on MS medium containing 2,4-D at 2, 3, 4 and 5 mg/L for callus induction. Inter-nodal segments initiated callus earlier than node and leaf. The highest amount of callus was found in MS medium with 3.0 mg/L 2,4-D and MS medium with 5.0 mg/L 2,4-D gave the poorest callu

Ahmed, R

Baten, MdA

Chowdhury, MSH

Khan, MMMH

Uddin, MB

Uddin, MS

English

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African Journal of Biotechnology Vol. 5 (13), pp. 1238-1240, 3 July 2006 Available online at http://www.academicjournals.org/AJB ISSN 1684–5315 © 2006 Academic Journals       Full Length Research Paper  In vitro propagation of Stevia rebaudiana Bert in Bangladesh  Mohammed Salim Uddin1, Mohammad Shaheed Hossain Chowdhury1, M. Muoztaba Mahfuzul Haque Khan1, Mohammad Belal Uddin1, Romel Ahmed1, Md. Azizul Baten2*  1Department of Forestry, Shah Jalal University of Science and Technology, Sylhet-3114, Bangladesh. 2Department of Statistics, Shah Jalal University of Science and Technology, Sylhet-3114, Bangladesh.  Accepted 28 March, 2006  An experiment was conducted on in vitro culture of Stevia rebaudiana Bert, an important non-caloric sweetening herb to explore its potential for micro-propagation. Leaf, nodal and inter-nodal segments of the selected herb as explant were cultured on MS medium containing 2,4-D at 2, 3, 4 and 5 mg/L for callus induction. Inter-nodal segments initiated callus earlier than node and leaf. The highest amount of callus was found in MS medium with 3.0 mg/L 2,4-D and MS medium with 5.0 mg/L 2,4-D gave the poorest callus.   Key words: In vitro propagation, 2,4-D, Stevia rebaudiana.   INTRODUCTION   Stevia rebaudiana Bert Belonging to the family Compositae, is one of the most valuable tropical medicinal plant. S rebaudiana is originally a South American wild plant (Katayma et al., 1976), but it could be found growing in semi-arid habitat ranging from grassland to scrub forest to mountain terrain. The plant has gained wide access to Pacific Rim countries, where in recent decades it is being cultivated domestically, used in its raw leaf form and is now commercially processed into sweetener. Seed germination of Stevia is often poor (Miyazaki and Wantenabe, 1974). Therefore, there are basically two options for multiplication; tissue culture and sstem cutting.  Stevia rebaudiana Bert is one of 154 members of the genus Stevia, which produces sweet steviol glycosides (Robinson, 1930; Soejarto et al., 1982). The first report of commercial cultivation in Paraguay was in 1964 (Katayama et al., 1976; Lewis, 1992). Sumida (1968) began a large effort aimed at establishing Stevia as a crop in Japan. Since then,  it  has been  introduced  as   a     *Corresponding authors E-mail: batenatsust.edu, baten_mathatyahoo.com. crop in a number of countries including Brazil, Korea, Mexico, United States, Indonesia, Tanzania and Canada (Lee et al., 1979; Goenadi, 1983; Shock, 1982; Saxena and Ming, 1988; Brandle and Rosa, 1992; Fors, 1995). In Brazil and Paraguay it grows wild. It is small shrubby perennial growing up to 65 cm tall, with sessile, oppositely arranged lanceolate to oblanceolate leaves, serrated above the middle. The property of the species that called attention to the plant was the intense sweet taste of the leaves and aqueous extracts. From the leaves of Stevia, stevioside, sweet crystalline diterpene glycosides are extracted. Pure extract stevioside is non-caloric and 30 times sweeter than sugar (Bhosle, 2004). Other attributes of this natural, high intensity sweetener include non-fermentable, non-discoloring, maintain heat-stability at 100°C and features a lengthy shelf life. The product can be added to tea and coffee, cooked or baked goods, processed foods and beverages. In the Pacific Rim countries like China, Korea and Japan Stevia is regularly used in preparation of food and pharmaceutical products. In Japan alone, an estimated 50 tons of stevioside is used annually with sales valued in order of $220 million Canadian (Brandle and Rosa, 1992). Currently S. rebaudiana production is centered in China with major market in Japan (Kinghorn and Soejarto,      Table 1. Composition of MS media (1 liter).  Category Chemicals Amount NH4NO3 1.65 g KNO3 1.90 g CaCl2.2H2O 0.44 g MgSO4.7H2O 0.37 g    Macro salts KH2PO4 0.17 g  FeSO4.7H2O   27.80 mg Na2EDTA2H2O 33.60 mg KI 0.83 mg H3BO4 6.20 mg MnSO4.4H2O 22.30 mg ZnSO4.7H2O 8.60 mg Na2MoO4.H2O 0.25 mg CuSO4.5 H2O 0.025 mg      Micro salts  CoCl2.6 H2O 0.025 mg  Myoinositol                           100.00 mg Nicotinic acid  0.05 mg Pyridoxine HCl 0.05 mg Thiamine HCl 0.05 mg Glycine 0.02 mg    Organic supplements  Sucrose 30.00 g    1985). No negative clinical reports have appeared in any of these countries where Stevia is readily available. For more than a decade, stevioside has approved and is widely used in Brazil. It is used as a table top sweetener, in soft drinks, baked goods, pickles, fruit juices, tobacco products, confectionary goods, jams and jellies, candies, yogurts, pastries, chewing gum and sherbets. Stevioside is of special interest to diabetic persons with hyperglycemia and the diet conscious.  The present investigation was undertaken to find out suitable sources of explants and suitable concentration of 2,4-D for callus induction in micro propagation of S. rebaudiana.   MATERIALS AND METHODS  Plant materials  The explants (leaf, nodal and inter-nodal segments) were collected from several days old in vitro generated Stevia rebaudiana at the Biotechnology Laboratory of Bangladesh Sugarcane Research Institute, Ishurdi of Pabna district. The explants were cut into small pieces (about 0.1 m long) and then were treated with 1% savlon for 5-6 min with constant shaking and washed thoroughly with distilled water. Then the explants were surface sterilized with a 0.1% mercuric chloride solution containing two-three drops of tween-80 for 5 min under aseptic condition and then washed  four  times  with  Uddin et al.       1239    sterilized distilled water. The explants were then inoculated aseptically into MS (Murashige and Skooge, 1962) medium with different concentrations and combinations of growth regulators (Table 1).    Preparation of stock solution  After mixing all salts and organic components the pH was adjusted to 5.7 by adding 1 M NaOH. Then 5.6 g agar was mixed to the media (by using microwave oven) for making it semi-solid. Total amount of media was then subdivided into four conical flasks each containing 250 ml. Then the hormone, 2,4-D, was added at 2, 3, 4 and 5 mg/L. Each 250 ml media was then poured into 18 test tubes. Thus a total of 72 test tubes were filled with media. In the same way other 36 test tubes were prepared and finally 108 test tubes were used in the experiment. The test tubes were autoclaved 121°C temperature and 15 psi for 20 min.   Callus induction medium  MS basal media supplemented with 2,4-D at varying concentrations (2-5 mg/l) were prepared for callus induction. After mixing all stock solutions and 3% sugar, pH of the medium was adjusted to 5.5-5.8. The agar (0.6%) was dissolved and media were dispersed in the test tubes and capped with cotton plugs. Test tubes containing media were autoclaved at 121°C at 15 psi for 20 min.    Culture environment  Unless mentioned specially, all cultures were grown in an air-conditioned culture room illuminated by 40 w white florescent tube light with intensity varied from 2000-3000 lux. The temperature of the culture room was maintained around 25°C. The photoperiod was maintained as 16 h light and 8 h darkness. Visual observation of culture was made every week and data were recorded after 2 weeks of inoculation.   RESULTS AND DISCUSSION  Among the explants used for the culture inter-nodal segments were found to be able to produce profuse callus. The results of callus production and multiplication are presented in Tables 2 and 3. Inter-nodal segments initiated callus earlier than leaf and nodal explants. The highest amount of callus was found in the MS medium with 3.0 mg/L 2,4-D. Length of day under which Stevia is cultivated has an effect on stevioside concentration, which is supported by Kinghorn and Soejarto (1985). The authors observed that in subtropical regions of the world, stevioside concentration is high in Stevia plant when it is cultivated under long days.  The result of the experiment and other earlier research report clearly support the possibility of propagating S. rebaudiana by adopting in vitro techniques. The climatic requirements of this tropical elite medicinal plant indicate that it can be introduced in the hilly areas of Sylhet and Chittagong. The unique selling points of Stevia sweetener are very strong in Bangladesh due to the presence of diabetic and other metabolic disease including obesity.  1240      Afr. J. Biotechnol    Table 2. Production of Stevia rebaudiana callus in different concentrations of hormones.                       +, Poor callus; ++, medium callus; and +++, profuse callus.   Table 3. Periods, colors and amounts of Stevia rebaudiana callus formation at different hormone concentrations.  Hormone(2,4-D) Days of callus initiation Color of callus Amount of callus Remarks 2 mg/L 10 Mainly brownish Medium  3 mg/L 11.5 Brownish to light green Highest Best callus 4 mg/L 11 Brownish Poor  5 mg/L 12 Brownish to blackish Poorest Very poor, often blackish color    Here Stevia in vitro propagation has been demonstrated with its overall potentiality and suitability. In vitro propagation can become an important alternative to conventional propagation and breeding procedures for wide range of plant species.   REFERENCES  Bhosle S (2004). Commercial cultivation of Stevia rebaudiana, Agrobios Newsletter. 3 (2):  43-45. Brandle JE, Rosa N (1992). Heritability for yield, leaf- stem ratio and stevioside content estimated from a landrace cultivar of Stevia rebaudiana. Canadian Journal of Plant Science. 72: 1263-1266. Fors A (1995). A new character in the sweetener scenario. Sugar J, 58:30. Goenadi DH (1983). Water tension and fertilization of Stevia rebaudiana on Oxic. Katayma O, Sumida T, Hayashi H, Mitsuhashi H (1976). The Practical pplication of stevia and R&D data (English translation). ISU Company, Japan. p. 747. Kinghorn AD, Soejarto DD (1985). Current status of stevioside as a sweetening agent for human use. In Wagner, Hikino H, Fransworth NR. (eds).Economic and medical plant research. Academic Press, London. Lee JI, Kang KK, (1979). Stdies on new sweetening resource plant Stevia rebaudiana in Korea.  Lewis WH (1992). Early uses of Stevia rebaudiana leaves as sweetener in Paraguay. Econ. Bot, 46: 336-337. Miyazaki Y, Wantenabe H (1974). Studies on the cultivation of stevia; on the propagation of plant (Eng. Abstr.). Jap. J. Trop. Agric. 17: 154-157. Murashige T, Skoog F (1962). A revised medium for rapid growth and bioassay with tobacco tissue cultures. Physiol. Plant 15: 473-479   Robinson BL (1930). Contributions from the Grey Herbarium of Harvard University. The Grey Herbarium of Harvard University, Cambridge.  SaxenaNC, Ming IS (1988). Preliminary harvesting characteristics of Stevia. Phys. Prop. Agic. Mat. Prod. 3: 299- 303. Shock CC (1982). Experimental cultivation of Rebaudia’s stevia in California. University of California Agronomy Progress Report No. 122. Soejarto DD, Kinghorn AD, Fransworth NR (1982). Potential sweetening agents of plant origin. J. Nat. Prod. 45: 590-599. Sumida T (1968). Reports on stevia introduced from Brazil as a new sweetness resource in Japan (English summary). J. Cent. Agric. Exp. Stn. 31: 1-71.    Test tube 2,4-D Explant 1 2 3 4 5 6 7 8 9 Leaf + + +++ + ++ + + + ++ Inter-node Failed + ++ ++ + + ++ ++ ++ 2 mg/L Node Failed + + ++ + + + + + Leaf + + + ++ + ++ ++ + + Inter-node +++ +++ +++ +++ +++ +++ +++ +++ +++ 3 mg/L Node Failed + + ++ ++ + + + + Leaf + + + ++ + + + + + Inter-node + ++ + + ++ ++ + + ++ 4 mg/L Node + + + + ++ + + + + Leaf + ++ ++ + + + + + + Inter-node + + + + + + + + + 5 mg/L Node + + + + + + + + + 

In vitro propagation of Stevia rebaudiana Bert in Bangladesh

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In vitro propagation of Stevia rebaudiana Bert in Bangladesh

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