10th U6+ Consortium of African Universities International Conference

Potato (Solanum tuberosum L.) is one of the world's most important food crops, but its productivity is highly constrained by drought stress, particularly in Sub-Saharan Africa where rainfall patterns have become increasingly erratic due to climate change. Despite the growing demand for drought-resilient potato cultivars, limited information exists on the physiological responses of available potato varieties to varying levels of water deficit, hindering effective breeding and selection efforts. This study aimed to assess the physiological drought tolerance of seventeen potato varieties under controlled greenhouse conditions and identify traits and genotypes associated with improved adaptation to water stress. The experiment was conducted using a completely randomized design with four watering regimes at 100%, 75%, 50%, and 25% field capacity. Drought stress was induced at 35 days after planting, coinciding with the tuber initiation stage. Physiological parameters including chlorophyll content, relative water content (RWC), stomatal conductance, leaf temperature, and biomass accumulation were evaluated. The results revealed significant differences (P < 0.05) among varieties and watering regimes for all physiological traits measured. Increasing water deficit significantly reduced chlorophyll content, RWC, stomatal conductance, and biomass, while leaf temperature increased. Plants subjected to severe drought stress (25% field capacity) recorded reductions exceeding 40% in biomass and chlorophyll content compared with the well-watered control. However, several varieties maintained significantly higher RWC, chlorophyll content, and stomatal conductance under both 25% and 50% field capacity, indicating superior drought tolerance mechanisms. The study demonstrated substantial genetic variability in drought response among the evaluated potato varieties and identified physiological traits that can serve as reliable indicators for screening drought tolerance. It is recommended that the tolerant varieties identified be further evaluated under field conditions and incorporated into potato breeding programmes aimed at developing climate-resilient cultivars for water-limited environments.