Genome-wide association study of vitamin E in sweet corn kernels

Vitamin E, consisting of tocopherols and tocotrienols, serves as a lipid-soluble antioxidant in sweet corn kernels, providing nutrients to both plants and humans. Though the key genes involved in the vitamin E biosynthesis pathway have been identified in plants, the genetic architecture of vitamin E content in sweet corn kernels remains largely unclear. In the present study, an association panel of 204 inbred lines of sweet corn was constructed. Seven compounds of vitamin E were quantified in sweet corn kernels at 28 days after pollination. A total of 119 loci for vitamin E were identified using a genome-wide association study based on genotyping by sequencing, and a genetic network of vitamin E was constructed. Candidate genes identified were involved mainly in RNA regulation and protein metabolism. The known gene ZmVTE4, encoding γ-tocopherol methyltransferase, was significantly associated with four traits (α-tocopherol, α-tocotrienol, the α/γ-tocopherol ratio, and the α/γ-tocotrienol ratio). The effects of two causative markers on ZmVTE4 were validated by haplotype analysis. Finally, two elite cultivars (Yuetian 9 and Yuetian 22) with a 4.5-fold increase in the sum of α- and γ-tocopherols were developed by marker-assisted selection, demonstrating the successful biofortification of sweet corn. Three genes (DAHPS, ADT2, and cmu2) involved in chorismate and tyrosine synthesis were significantly associated with the α/γ-tocotrienol ratio. These results shed light on the genetic architecture of vitamin E and may accelerate the nutritional improvement of sweet corn.