Genome-Wide Association Analysis for Fe and Zn Concentration in Sorghum Grains Identifies the Potential Candidate Genes for Sorghum Biofortification

Micronutrient deficiency especially iron and zinc is widely reported in Semi-Arid Tropics regions across globe. Genetic enhancement is one of the alternatives to reduce micronutrient malnutrition. We evaluated a set of 361 genotypes involving sorghum hybrid parents, improved cultivars and core collection germplasm accessions, and found large variability in grain Fe and Zn concentration. Genome-wide association study (GWAS) utilizing ~556k SNPs identified by following genotyping-by-sequencing (GBS) approach and the Fe/Zn concentration revealed marker-trait associations (MTAs) for Fe concentration on chromosomes 2, 4 and 8; and for Zn on chromosomes 1, 3 and 5. SNPs associated with days to flowering on chromosomes 3 and 6, and for plant height on chromosome 1 and 7 (coincided with the earlier studies). In-silico homology search of 91 candidate genes governing grain Fe and Zn concentration in rice, wheat, maize and barley identified 77 genes homologous with sorghum genome. Loci found associated with Fe and Zn are localized very close to the homologous genes (OsNAS, OsZIP, HvNAAT, OsVIT, OsNRAMP, HvDMAS, OsYSL, OsNAC, etc.) from other cereals that might be associated with similar function(s) in sorghum. So far, QTL and genes for Fe and Zn were not reported in sorghum; hence we discussed these results in relation to known homologous genes from other cereals present within and around the vicinity of these trait-associated SNPs. This suggested that loci present near these corresponding genes in sorghum are the potential candidates for increasing Fe and Zn concentration in sorghum through biofortification to combat micronutrient malnutrition.