Response of three sorghum (Sorghum bicolor L. Moench) varieties to soil moisture stress at different developmental stages

Abstract

Three varieties (Segaolane, Mahube and Phofu) of sorghum (Sorghum bicolor L. Moench) that were selected in Botswana, were water-stressed at the vegetative, booting and flowering stages in a pot experiment under glasshouse conditions. Stomatal conductance was reduced by water stress but at the vegetative stage all varieties were able to recover to their pre-stress conductance levels. Total leaf area, effective (green) leaf area, specific leaf weight and specific leaf area all decreased with stress while root/shoot ratio increased. Grain yields were significantly (p < 0.05) lowered by stress, especially when this was applied at the booting stage. Although varietal differences in yield were not significant, based on overall performance the older Segaolane appears superior to the more recently developed varieties Phofu and Mahube, in conditions of hydrological unpredictability and intermittent water stress.