The effect of salicylic acid on the yield of vegetative organs and active ingredients of stevia (Stevia rebaudiana Bertoni) under drought stress

This study was performed to investigate the effect of drought stress and salicylic acid on quantitative and qualitative yield and biochemical and physiological properties of stevia. An experiment was carried out based on a split plot design and randomized complete blocks with 3 replications in a research farm in Sarableh, Ilam during 2020-2021. Drought stress in 3 levels (control or 100% of field capacity, 75% of field capacity, and 50% of field capacity) and salicylic acid treatment in 2 levels (non-consumption and foliar application with a concentration of 1 mM) were applied. Plant height, number of periphery shoots, dry weight of stems and leaves, total dry matter yield, extractable sugars, and protein, proline, total chlorophyll, stevioside, glycoside, rebaudioside, and phenolic compound contents were assayed in the study. Findings showed that the highest total dry matter yield were obtained in irrigation control and salicylic acid consumption (77.2 g per plant), showing 34% increase compared to the lowest total dry matter yield obtained under 50% of field capacity irrigation and no salicylic acid consumption 34%. Also, in all drought stress treatments, applying salicylic acid improved total dry matter yield. In the treatment with no drought stress, the lowest sugar contents per plant were observed and in the treatment with salicylic acid the glucoside contents were more than the control. In general, drought stress reduced the amount of sugar and other growth traits of stevia plants. Applying salicylic acid in addition to improving the quantitative and qualitative traits of the stevia, improved the plant’s yield under various levels of drought stress, which is very important