Effects of water stress on growth, yield, quality and physiological responses of two stevia (Stevia rebaudiana Bertoni) varieties in Rabat region, Morocco

Since no information is available about theresponse of stevia (Stevia rebaudianaBertoni) to water stress under Moroccan conditions. This study was aimed at evaluating the effects of water stress on growth, yield, quality and physiological responses of two stevia varieties (Canada and Candy). Three water regimes were applied: R100 (100% of field capacity (FC)), R80 (80% of FC) and R50 (50% of FC) as determined by pot weight. Water stress significantly reduced stomatal conductance (Gs), photosynthetic rate (A) and transpiration rate (E) by 72.50%, 78.54% and 74.45 % at R50, respectively as compared to R100. With the continuing of water stress time, plant allocated less plant height leading to reductions of 20.27% at R50 as compared to R100. All of the above responses led to reduced dry leaf yield. Bycontrast, the stevioside, rebaudioside A and total steviol glycoside contents were increased in R50 stevia leaves than R100 (23.58%, 13.50% and 11.73%, respectively). The cv Candy displayed a higher dry leaf yield (34.33g/plant) and leaf physiological responses compared to cv Canada, which experienced a great decrease. By contrast, the cv Canada recorded a higher total steviol glycoside content (19.63%) than the cv Candy (12.63%). The interaction effects indicate that cv Candy, for R100, displayed a greater dry leaf and SG yields, while these parameters were greatly reduced under R80 and R50. By contrast, the cv Canada always showed a lower dry leaf and steviol glycoside yields and a greater total steviol glycoside contents, that enable it to have a betteradaptation to water stress conditions. The variation of cv Canada and cv Candy responses to water stress suggested the higher adaptation of cv Canada to water stress compared to cv Candy