Grain yellowness is an effective predictor of carotenoid content in global sorphum populations

Authors: MCDOWELL, RACHEL - Colorado State University; BANDA, LINLY - Colorado State University; Bean, Scott; MORRIS, GEOFFREY - Colorado State University; RHODES, DAVINA - Colorado State University

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/4/2024
Publication Date: 10/24/2024
Citation: Mcdowell, R., Banda, L., Bean, S.R., Morris, G.P., Rhodes, D.H. 2024. Grain yellowness is an effective predictor of carotenoid content in global sorphum populations. Scientific Reports. 14. Article 25132. https://doi.org/10.1038/s41598-024-75451-9.
DOI: https://doi.org/10.1038/s41598-024-75451-9

Interpretive Summary: Carotenoids are pigments found in yellow, red, and orange fruits and vegetables and some types are provitamin A compounds. Vitamin A deficiency affects millions of people worldwide, contributing to decreased immune defenses and increased incidence of blindness and death in children under the age of five. Sorghum grain contains carotenoids, but the concentrations are low compared to fruits and vegetables. Biofortification of sorghum through marker-assisted breeding could significantly contribute to alleviating the incidence of vitamin A deficiency in regions where sorghum is a staple crop. Using grain color as a predictor of carotenoid concentration is potentially a faster and cheaper method than analytical methods. Thus, this research characterized the color of sorghum grain in the USDA gene bank to determine if color could be used to predict carotenoid content and composition in sorghum. The use of quick and inexpensive screening of sorghum grain collections would benefit the development of sorghum lines with increased carotenoid content.

Technical Abstract: Identification of high carotenoid germplasm is crucial to assist breeders in provitamin-A biofortification of sorghum (Sorghum bicolor [L.] Moench). High-performance liquid chromatography is the gold standard for carotenoid quantification, however, it is not feasible for large scale phenotyping due to its high cost and low throughput. In this study, we tested the feasibility of using grain color as a high-throughput method of carotenoid biofortification breeding. We hypothesized that visual, color-based selection can be an effective strategy to identify high-carotenoid accessions. Yellow grain had significantly higher carotenoid content than red, brown, and white grain. The degree of yellowness could distinguish the presence or absence of carotenoids, but could not distinguish carotenoid concentrations within yellow-only accessions. The degree of luminosity of the grain, however, was able to better predict carotenoid concentrations within yellow-only accessions. Genome-wide association studies identified significant marker-trait associations for qualitative and quantitative grain color traits and carotenoid concentrations near carotenoid pathway genes—ZEP, PDS, CYP97A, NCED, CCD, and LycE—three of which were common between grain color and carotenoid traits. These findings suggest that using grain color as a method for screening germplasm may be an effective high-throughput selection tool for prebreeding and early-stage breeding in carotenoid biofortification.