Refining steviol glycoside production in Stevia rebaudiana via elicitors under sodium stress
摘要
Stevia rebaudiana Bertoni, a natural sweetener plant, could be a potential wholesome replacement for the harmful artificial sweeteners available in market. It also has a significant commercial potential due to the presence of plant specialized metabolites or secondary metabolites like stevioside (stev) and rebaudioside A (reb A). In this study, a novel technique was devised to optimize the secondary metabolite content in Stevia by integrated application of salinity (NaCl), putrescine (PUT) and sodium nitroprusside (SNP). Stevia plants were grown at two different salinity levels (15 mM and 30 mM) under polyhouse conditions. PUT and SNP were applied as exogenous foliar treatments at two different concentrations each i.e., PUT (1 mM and 2 mM) and SNP (150 µM and 200 µM). Our results demonstrated that salinity stress significantly impaired the growth and development of Stevia rebaudiana Bertoni, evidenced by reduced stev, reb A, plant height, number of leaves, leaf area, chlorophyll content, relative water content, and K+ concentration. The exogenous application of PUT and SNP neutralized the adverse consequences of salinity stress and enhanced the concentration of these parameters significantly. Optimum concentrations of these parameters (except steviol glycosides) were noticed for 1 mM PUT and 150 µM SNP under 15 mM salinity stress. The highest amount of stevioside (15.44%) was obtained for 200 µM SNP spray under 30 mM salt stress condition, which was nearly three times higher than the control (5.66%) whereas optimum reb A (8.20%) was found in plants treated with 2 mM PUT under 30 mM NaCl stress, representing a substantial increase compared to the control (1.46%). These results indicate the potential of SNP and PUT as efficient elicitors for enhancing steviol glycoside production under salt stress.