Effect of abiotic stress on growth parameters and steviol glycoside content in Stevia rebaudiana (Bertoni) raised in vitro

Stevia rebaudiana (Bertoni) is a producer of diterpenoid steviol glycoside (SGs), which is highly sweet compound, non-toxic, non-mutagenic and has negligible effect on blood glucose. Therefore, the aim of present work was to study the effect of four chemicals (NaCl, Na2CO3, Proline and Polyethylene glycol) on growth parameters and SGs production in S. rebaudiana shoots cultured in vitro. For this, in vitro raised nodal explants of Stevia were cultured on MS medium supplemented with 2.0 mgl(-1)of kinetin and different concentrations of NaCl (0.05-0.20%), Na2CO3(0.025-0.10%), Proline (2.5-10mM) and Polyethylene glycol (2.5-10%) for four weeks, and incubated at 24 +/- 1 degrees C and 22.4 mu molm(-2)s(-1)light intensity provided by white fluorescent tubes with a photoperiod of 16 h. Among all the chemicals tested, NaCland Proline showed good growth of shoots but Na2CO3 and PEG showed poor growth in comparison to control. A significant reduction in shoot growth (i. e., shoot length, number of shoots per node and multiplication fold) was noticed with different concentrations of chemicals tested (P <= 0.05). Maximum shoot length (5.83 +/- 0.01 cm) was observed with 7.5 mM of Proline concentration followed by 0.05% NaCl (5.45 +/- 0.08 cm), 0.025% Na2CO3(4.05 +/- 0.06 cm) and 2.5% PEG (2.52 +/- 0.06 cm). Stress showed better results pertaining to SGs production in stress treated in vitro plants than control. Maximum (2.60%) amount of total SGs (Stevioside and Rebaudioside A) were found with shoots treated with 0.025% Na2CO3 followed by 5.0 mM Proline (1.65%), 0.10% NaCl (1.25%) and 5% PEG (1.15%), which were 3.3, 2, 1.6 and 1.5times higher than control (0.79%) respectively. It can be concluded that, in spite of causing some growth reduction, application of chemical stress can enhance the production of SGs up to three fold compared to control plants. (C) 2016 Elsevier GmbH. All rights reserved.