Sorghum Germplasm Profiling to Assist Breeding and Gene Identification for Biofortification of Grain Mineral and Protein Concentrations.

Sorghum (Sorghum bicolor) is the world’s fifth most important grain crop, and is a widely consumed staple in subtropical semi-arid regions of Africa and Asia.  Biofortification of sorghum by increasing mineral micronutrient (especially iron and zinc) and protein concentration is of widespread interest.  Here, we report profiling of a panel of 95 sorghum accessions of wide diversity for concentration of eight minerals (Cu, Fe, K, Mg, Mn, P, S, and Zn), crude protein, and digestibility.  Accessions were chosen from a prior large-scale screen for protein concentration (2882 accessions).  The extreme high (10 accessions) and low (19 accessions) protein lines were selected, and 66 accessions that are also in an association mapping panel.  We observed a normal distribution of grain size, digestibility, and mineral concentrations, in most cases with a range of >2-fold.  Several minerals showed strong positive correlations with protein concentration, suggesting that mineral and protein density in grain can be improved together.  Several minerals were positively correlated, (i.e. Fe and Zn), suggesting that improving accumulation of one of these minerals might also result in increases in others.  None of the mineral or protein concentrations were correlated with digestibility.  Therefore, sorghum breeders can likely select for improved digestibility independently of mineral or crude protein concentration.  Sufficient diversity is present in sorghum germplasm to breed for increased seed mineral and protein.  Association mapping may allow identification of specific genes that can be used in transgenic approaches to develop lines with higher accumulation of nutrients in grain.