Phenotypic BLUP and Drought Tolerance Indices of Stay Green Introgressed Sorghum Lines Grown under Two Different Water Management Conditions in Ethiopia

Post-flowering drought stress is one of the main abiotic factors affecting sorghum production and threatening food security globally, including in Ethiopia. Therefore, it is crucial to develop high-yielding and drought-tolerant sorghum varieties that are adapted to drought environments in the country. The objectives of this study were to analyze the yield potential of the stay green QTLs introgressed sorghum lines and their parents, and to identify useful drought tolerant indices. A field evaluation was conducted using a 5x5 triple lattice design under non-stress (Ns) and drought stress (Ds) growing conditions at the Kobo testing site during the post-rainy cropping season of 2012. The results showed that genotypic differences were highly significant for grain yield (Y), staygreen (SG), total chlorophyll per unit area (TCM), chlorophyll contents at flowering (CF) and maturity (CM) traits in Ns and Ds growth conditions, as well as for all drought tolerance indices. Some stay green introgressed sorghum lines showed increased Y and traits linked to chlorophyll related traits compared to the recurrent parents and stay green donor parent in Ds. The drought tolerance indices of mean productivity, geometric mean productivity, harmonic mean, yield index, and stress tolerance index were positively and significantly associated with NsY and DsY, allowing for the selection of high yielding and drought tolerant genotypes in drought-prone growing environments. Based on their drought tolerance indices, yield potential, and chlorophyll-related traits, five stay green QTLs introgressed sorghum lines (Meko x B-35-8, Meko x B-35-25-15, Meko x B-35-13, Teshale x B-35-12, and Gambella x B-35-01) could be given priority for valorization in sorghum improvement programs. Further research on marker-assisted introgression is required in order to incorporate multiple stay green QTLs into the genome of the high yielding sorghum varieties. This could aid in determining which stay-green QTL allele combinations are most likely to work together synergistically in drought-stressed environments.