Glasshouse Evaluation of Drought Susceptibility in Four Commercial Potato Cultivars in Southern Africa

Potato (Solanum tuberosum L.) is a cool-season crop highly sensitive to abiotic stresses, with drought emerging as one of the most significant yield-limiting factors for yield. A glasshouse trial was conducted to evaluate the drought response of four commercially grown potato cultivars in southern Africa - BP1, Up-to-Date, Hertha and Mondial - under four water regimes: control (80% field water capacity), mild (60% field water capacity), severe (40% field water capacity), and extreme stress (30% field water capacity). Morpho-physiological traits, biomass, and yield components were measured, alongside stress tolerance indices (Stress Tolerance Trait Index, Stress Tolerance Index, Yield Index, Relative Stress Index, and Tolerance Index). The experiment was carried out with a completely randomised design, replicated four times per variety. The results indicated that reduced water availability had a significant impact on all measured traits. The most severe reductions occurred under the 30% FWC treatment. Among the four cultivars, BP1 exhibited the highest drought tolerance (Stress Tolerance Trait Index = 72.03%), followed by Mondial, Hertha, and Up-to-Date. These findings provide critical insights into varietal performance under water stress and support the selection of drought-resilient potato genotypes for cultivation in southern Africa.