World Applied Sciences Journal 25 (8): 1231-1238, 2013 ISSN 1818-4952 © IDOSI Publications, 2013 DOI: 10.5829/idosi.wasj.2013.25.08.13378 Corresponding Author: Nadia Gad, Department of Plant Nutrition, National Research Centre Dokki, Egypt . 1231 Effect of Cobalt Supplement on Stevia Rebaudiana Bert. Growth and Yield Nadia Gad and Hala Kandil Department of Plant Nutrition, National Research Centre Dokki, Egypt Submitted: Sep 13, 2013; Accepted: Oct 21, 2013; Published: Oct 30, 2013 Abstract: A field experiment was conducted at Research and Production Station, National Research Centre, El-Nubaria Site, Beheara Governorate, Delta Egypt under drip irrigation system during the successive season, 2011. Experiment was carried out to evaluate the response of stevia herb yield and sweeteners content to cobalt supplement. Stevia seedlings were irrigated with cobalt once at concentrations: 0.0, 2.5, 5.0, 7.5, 10.0, 12.5, 15.0 and 17.5 ppm. The obtained results are summarized in the following: Cobalt has a significant promotive effect on all growth and yield parameters as well as nutritional and chemical content compared with control. Cobalt significantly increase stevia leaves content of sweetners such as glycosids, steviosides and rebaudiosides compared with untreated plants. Cobalt at 12.5 ppm recorded the greatest figures. Cobalt at 12.5 ppm increased glycoside to 34.11 and 37.0%, steviosides to 27.6 and 31.6%, rebaudiosides to 44.5 and 45.1% respectively in two cuts. Increasing cobalt in plant media more than 12.5 ppm the promotive effect decreased. Key words: Cobalt Stevia Rebaudiosides Sweetners Glycosides Steviosides INTRODUCTION but, on the contrary, it is healthful, as shown by long Stevia (Stevia rebaudiana Bertoni) is a sweet herb (3) It can be employed directly in its natural state, (medical plant) native of Paraguay. It has been widely (Pulverized leaves). (4) It is much cheaper than saccharine. cultivated in the world for the sweet diterpene glycosides Stevia is an endemic herb non-caloric nature. Stevia that is mainly contained in its leaves. leaves and their compounds are used in many therapeutic Roy et al. [1] reported that the leaves of stevia are applications such as diabetes, obesity and plague free from carbohydrates and calories and hence, it can be retardant, hypoglycemic, indigestion, dental health, yeast used safely by diabetic patients. It has now been infection, oral health, skin toning and healing burns and recognized that stevia has many uses for human beings wounds. Stevia is also used a sweetening agent in especially when it acts as a sugar substitute for those products like biscuit, Jams, chocolates and ice-cream [7]. persons with blood sugar problems. Taking the sweetening powder of the stevia sugar into The fresh leaves itself 30 - 45 times [2]. Stevioside is consideration: these 400 kg stevia sugar are equivalent to a glycoside and it has sweetening power 100-400 temes about 80000 sweetening units. Note that one Fadden of than sucrose [3,4]. Stevioside concentrations usually "sugar can" produces about 5.000 sweetening units and range from 3 - 10 % of leaf dry weight; rebaudloside- A one Fadden of "sugar beet" produces about 3.500 (400 times sweeter than sugar) is less concentrated sweetening units. A sweetening unit is equivalent to the ranging from 1 - 3 % [5]. Brandle [6] stated that the sweetness of one kilogram of sucrose. The stevia plant principal importance of stevia is due to the possibility of was introduced to agriculture of Egypt in order to produce substituting advantages over saccharine: (1) It is not toxic a natural sweetener than can cover some of the lack of experience. (2) It is a sweetening agent of great power.