Toward marker-assisted breeding for bioaccessible provitamin A in sorghum: genetic and environmental basis of carotenoid bioaccessibility

Abstract Vitamin A deficiency is a critical global health issue, particularly in regions reliant on sorghum, a staple cereal with low provitamin A carotenoid (PVAC) content. Enhancing bioaccessible PVAC in sorghum grain is essential for effective biofortification, yet the genetic basis and environmental influences on carotenoid bioaccessibility are not well characterized. We used an in vitro digestion assay, genomic mapping, and multi-environment trials on diverse sorghum germplasm and a biparental family to quantify genetic and environmental influences on carotenoid bioaccessibility. We discovered substantial genetic variation for bioaccessible carotenoid traits, with heritability that varied by trait and year; notably, the ratio of 𝛼-branch to β-branch carotenoids showed the highest and most stable heritability across environments and generations. Bioaccessibility quantitative trait loci (QTL) colocalized with carotenoid content QTL, and phytates, phenolics, and mineral content showed environment-dependent associations with reduced bioaccessibility. Markers linked to these QTL explained up to 67% of the variation in 𝛼- to β-branch carotenoid ratios across diverse germplasm and environments, supporting marker-assisted selection strategies that target metabolic flux toward β-branch carotenoids to improve bioaccessible provitamin A in sorghum, offering a promising approach to reduce vitamin A deficiency in vulnerable populations.