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 gamma-tocopherol methyltransferase, was significantly associated with four traits (alpha-tocopherol, alpha-tocotrienol, the alpha/gamma-tocopherol ratio, and the alpha/gamma-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 alpha- and gamma-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 alpha/gamma-tocotrienol ratio. These results shed light on the genetic architecture of vitamin E and may accelerate the nutritional improvement of sweet corn. 2019 Crop Science Society of China and Institute of Crop Science, CAAS. Production and hosting by Elsevier B.V. on behalf of KeAi Communications Co., Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).