Dynamics of yield components and stevioside production in Stevia rebaudiana grown under different planting times, plant stands and harvest regime

Stevia rebaudiana (Bertoni) Bertoni is well known because of its accumulation of the sweet-tasting ent-kaurene diterpeneoid glycoside, which tastes about 300 times as sweet as sucrose. Although stevioside is one of the most abundant and best analyzed, more than 30 additional steviol glycosides so far have been identified and described. Stevioside concentration in the leaves is known to vary widely, depending on the growing conditions and agricultural practices. The present study aimed to examine the feasibility of growing Stevia as an open-field crop in Israel. In order to determine the agricultural practices required for optimizing Stevia biomass production and stevioside yield, effects of planting and harvest times upon plant development, biomass yield components, and stevioside content were examined. The optimal planting season, manifested in intensive plant development and maximal plant biomass yield, was at the beginning of spring, i.e., mid-March to early April. A minimal stand of 10 plants/m2 was found more favorable than lower stands of 6, 8, or 10 plants/m2′'. The optimal harvesting time, with the highest stevioside yield of about 30 g/m2 was at the beginning of September, prior to flowering initiation. Moreover, harvesting at this time yielded increased leaf biomass, highly suitable for commercial stevioside extraction. Thus, Stevia rebaudiana offers substantial potential for introduction as a commercial agricultural crop for stevioside production in Israel.