Natural variation further increases resilience of sorghum bred for chronically drought-prone environments

Moisture stress is one of the major constraints for crop production in African Sahel. Here, we explore the potential to use natural genetic variation to build on the inherent drought tolerance of an elite sorghum cultivar (Teshale) bred for Ethiopian conditions including chronic drought, evaluating a backcross nested-association mapping population using 12 diverse founder lines crossed with Teshale under three drought-prone environments in Ethiopia. All twelve populations averaged higher head exsertion and lower leaf senescence than the recurrent parent in the two highest-stress environments, reflecting new drought resilience mechanisms from the donors. 154 QTLs were detected for eight drought responsive traits – the validity of these were supported in that 113 (73.4%) overlapped with QTLs previously detected for the same traits, concentrated in regions previously associated with 'stay-green' traits. Allele effects show that some favorable alleles are already present in the Ethiopian cultivar, however the exotic donors offer rich scope for increasing drought resilience. Using model-selected SNPs associated with eight traits in this study and three in a companion study, phenotypic prediction accuracies for grain yield were equivalent to genome-wide SNPs and were significantly better than random SNPs, indicating that these studied traits are predictive of sorghum grain yield.