Stress Tolerance in Sugar Beet under Various Drought Stress Cycles

Background: Drought stress is one of the most common and important environmental factors affecting crop growth and production. Sugar Beet (Beta vulgaris L.) is a temperate halophyte crop, but it is sensitive to water scarcity, which can reduce its growth and yield. Methods: To study the performance of tropical sugar beet under water deficit conditions, a pot experiment was conducted in January to May 2021, using a completely randomized design with three replicates. First and second cycles of drought stress were imposed on seven-week-old sugar beet plants (LS-6 tropical variety). The first phase of stress involved with 5, 10, 15 and 20 days of irrigation withholding to 8 treatments, followed by 15 days of normal watering. Then, half of the treatments were subjected to a second cycle of drought by imposing 3 days of stress. Drought effects were studied in terms of growth, physiological, biochemical and yield characteristics. Result: Water deficit hampered plant growth by reducing leaf area and leaf area index. A marked decrease in relative water content and chlorophyll stability index was also observed. Proline and total soluble carbohydrate content increased compared to the control, while starch content was decreased. However, after 15 days of watering under the second duration of stress, all parameters recovered against control, with a slight effect compared to single-stressed treatments. Yield reduction was observed under severe stress 20 days water withholding, whereas the drought effect was not significant on the harvest index.