Genetic diversity and drought adaptation in an Ethiopian sorghum landrace collections: Phenotypic traits and breeding implications for sub-Saharan drylands

Sorghum ( Sorghum bicolor L.) is a key drought-adapted staple in sub-Saharan Africa, yet the drought tolerance of diverse landraces remains underexplored. This study revealed significant genetic variation among Ethiopian landraces under contrasting water regimes, identifying promising high-yielding genotypes for breeding. The experiment was conducted during the 2020 and 2021 growing seasons across two Ethiopian agroecological zones—irrigated dry lowland (Melkassa) and naturally drought-prone dry lowland (Miesso)—using a diverse panel of 358 Ethiopian sorghum landraces. Spatial and multi-environment modeling improved the accuracy and reliability of best linear unbiased predictions (BLUPs), enabling robust genotype evaluation across environments. Drought stress decreased growth duration, grain yield, and related traits, lowering genetic variance and heritability and reducing selection efficiency. Irrigated conditions led to a 44.6% higher mean yield and a 14% higher thousand seed weight. Ten sorghum landraces consistently displayed superior yield performance across drought stress and non-stress environments, while five sorghum landraces G18, G132, G141, G338 and G296 exhibited low tolerance index (TOL) values, indicating good stress resilience. Hierarchical clustering divided sorghum landraces into seven geographically linked groups, emphasizing the value of regional diversity for enhancing genetic variation and stress resilience in breeding programs. Grain yield was positively correlated with head weight, thousand seed weight, and head width, suggesting these traits are useful indirect selection criteria. The current study showed significant genetic variation among Ethiopian sorghum landraces under irrigated and drought-stress conditions for strategic conservation and breeding in similar agro-ecologies. The results highlight valuable genetic diversity within Ethiopian sorghum landraces for breeding climate-resilient cultivars in drought-prone agro-ecologies.