Drought Recovery Responses in Grain Sorghum: Insights into Genotypic Variation and Adaptation

In Uganda, rain-fed crops frequently encounter cycles of drought stress followed by rewatering. Thus, with escalating fluctuations in water supply, drought recovery has become a critical focus for future sorghum drought phenotyping, genetics, and breeding research. However, there is currently a low knowledge of the drought recovery potential of prospective genotypes in Uganda’s National Sorghum Improvement Program. The present study aimed to assess the response of selected genotypes to rewatering after drought. Sixteen sorghum genotypes and two check varieties were evaluated under two contrasting moisture regimes: well-watered and drought stress-rewatering in a split-plot layout using a randomized complete block design (RCBD). Watering regimes were assigned to whole plots, while sorghum genotypes were assigned to subplots, with three replications. The results showed highly significant effects (p < 0.05) of drought stress on key agronomic traits, decreased dry weight, grain weight, and biomass yield by 39%, 43% and 37%, respectively, and delayed flowering by an average of 11 days. Key genotype-specific traits associated with drought recovery included rapid rehydration, compensatory growth, and maintenance of high relative chlorophyll content, all of which were essential for optimizing yields after stress. Leveraging drought tolerance indices, genotypes were ranked by their recovery potential and further classified into four distinct groups (A–D) based on their yield performance and stability under the two watering regimes. Genotypes in category A demonstrated high yield stability and strong recovery potential. Conversely, genotypes in category D exhibited the poorest recovery response. Overall, the information generated from this study will support future sorghum breeding efforts for drought resilience.