Responses of stevia (Stevia rebaudiana Bertoni) to salinity conditions

Abstract

The sweet herb or ka'a he'ẽ in the Guarani language (Stevia rebaudiana Bertoni) is a native plant of Paraguay, which produces a natural sweetener, 300 times sweeter than sucrose. The consumption of stevia has spread to numerous countries due to its beneficial properties for health. To meet the global demand for stevia, the production must be optimized through the use of improved varieties cultivated in different environmental conditions. This is an important fact, given the challenges related to climate change, such as salinity, opting for varieties that adapt to these conditions generates a positive impact on the dissemination of the crop. This research was aimed to determine the response of the Eirete variety of S. rebaudiana to saline stress conditions by evaluating selected biochemical and growth parameters. Vitroplants propagated in Murashige and Skoog culture medium (MS) supplemented with 0, 25, 50, 75, or 100 mM NaCl were used in the study to identify the concentration that reduced growth by 50% (GR50) and with 0, 50, 100, 150, and 200 mM NaCl to determine the concentration that caused the death of 50% of the individuals (LD50). After the evaluation of biochemical and growth parameters carried out at the dose corresponding to GR50, a significant decrease in the height, fresh and dry weight of the aerial parts, and fresh weight of the roots was found. Substantial increases in the proline concentration and the root/shoot ratio were also observed. There was no significant alteration of the dry weight of the roots and the content of soluble sugars or chlorophylls. Based on these results, it can be concluded that the development of vitroplants of S. rebaudiana var. Eirete is reduced by increasing concentrations of NaCl in the culture medium; however, our results suggest that stevia plants can be cultivated in moderate saline conditions.