Genetic variability assessment of post-flowering drought stress tolerance in selected sorghum (Sorghum bicolor L. Moench) genotypes

Abstract

Drought is a severe abiotic stress that significantly limits crop production in sub-Saharan Africa. Different sorghum (Sorghum bicolor L. Moench) genotypes respond differently to pre-flowering and post-flowering drought stresses. In Ethiopia, post-flowering has significant influence on yield reduction. The aim of this study was to assess the response of 216 sorghum accessions under post-flowering drought stress and non-stress conditions. The experiment was conducted at Melkassa Agricultural Research Center and Werer Agricultural Research Center in Ethiopia, using a row-column design with two replications under stress and non-stress conditions. The results from both sites indicated a significant difference among accessions in both water-stress and well-water regimes, suggesting that the tested accessions were diverse. While the phenotypic variance was higher than the genetic variance for all characters under study, the narrow range of difference indicated that most of the characters were less influenced by the environment. Stress tolerance index, mean productivity, geometric mean productivity, harmonic mean productivity, and yield index were identified as appropriate indices to select drought-tolerant sorghum accessions. The data from both sites on drought tolerance indices showed that drought stress in sorghum can significantly reduce grain yield. Selection by these indices can help identify a genotype with desirable yield in both stress and non-stress conditions. Based on significant associated indices, cluster analysis showed that the accessions tended to group into four clusters: tolerant, semi-tolerant, semi-sensitive, and sensitive. Among all accessions, Acc#222888, Acc#28546, and Acc#216739 were identified as the most drought-tolerant in both research sites, and they might be a potential source of genetic material for drought tolerance. The study highlights the importance of evaluating sorghum genotypes for post-flowering drought resistance under different irrigation conditions to identify potential sources of genetic material for breeding programs aimed at developing drought-tolerant sorghum varieties.