Natural Variation and Genome‐Wide Association Study of Antioxidants in a Diverse Sorghum Collection

Abstract

Consumption of polyphenol‐rich food is associated with decreased risk of oxidative stress‐related chronic diseases. Sorghum, a major food and feed cereal crop, has many polyphenol‐containing accessions with high antioxidant activity in the grain. However, many of these polyphenol‐containing accessions are not high‐yielding or food‐grade varieties. The natural variation in sorghum grain polyphenols can be used to develop high‐yielding, health‐promoting specialty food types through marker‐assisted breeding. To identify new antioxidant‐rich germplasm, we quantified antioxidant activity, total polyphenols, and condensed tannins in whole kernel flour in 266 accessions from the genetically and phenotypically diverse Sorghum Association Panel. Antioxidant activity, total polyphenols, and condensed tannins were in the ranges of 9.6–325.1 μmol of trolox equivalents (TE)/g, 0.8–18.8 g of gallic acid equivalents/kg, and 0–65.5 g of catechin equivalents/kg, respectively. Twenty‐three accessions were rich sources of antioxidant activity, with PI534144 (SC84; 325.1 μmol of TE/g) and PI534117 (SC991; 237.0 μmol of TE/g) possessing the highest values. To identify quantitative trait loci associated with sorghum grain antioxidant traits, we conducted a genome‐wide association study with 404,628 single nucleotide polymorphism markers. Many significant associations were identified, including two homologs of Arabidopsis (Arabidopsis thaliana) transparent testa (TT) genes TT10 and TT4. This study provides information that can help breeders incorporate health‐promoting traits into elite breeding lines.