Genome-wide association and genomic prediction models of tocochromanols in fresh sweet corn kernels

Authors: BASEGGIO, MATHEUS - Cornell University; MURRAY, MATTHEW - University Of Wisconsin; MAGALLANES-LUNDBACK, MARIA - Michigan State University; KACZMAR, NICHOLAS - Cornell University; CHAMNESS, JAMES - Cornell University; Buckler, Edward - Ed; SMITH, MARGARET - Cornell University; DELLAPENNA, DEAN - Michigan State University; TRACY, WILLIAM - University Of Wisconsin; GORE, MICHAEL - Cornell University

Submitted to: The Plant Genome
Publication Type: Review Article
Publication Acceptance Date: 8/6/2018
Publication Date: 11/21/2018
Citation: Baseggio, M., Murray, M., Magallanes-Lundback, M., Kaczmar, N., Chamness, J., Buckler IV, E.S., Smith, M.E., Dellapenna, D., Tracy, W.F., Gore, M.A. 2018. Genome-wide association and genomic prediction models of tocochromanols in fresh sweet corn kernels. The Plant Genome. 12:180038. https://doi.org/10.3835/plantgenome2018.06.0038.
DOI: https://doi.org/10.3835/plantgenome2018.06.0038

Interpretive Summary: Sweet corn is a popular vegetable in the United States, but contributes little vitamin E and antioxidants to the diet of the consumer. Vitamin E is made up of lipid-soluble molecules known as tocochromanols, and increasing the level of tocochromanols in sweet corn could improve human health and nutrition. This study identified the genes associated with the variation of levels of tocochromanols (antioxidants) and Vitamin E in fresh kernels. We found one gene that accounts for the highest level of Vitamin E activity and two genes that control the content and composition of antioxidants. We also observed that super sweet corn lines have, on average, greater amounts of antioxidants due to the higher frequency of favorable genes in these lines. Genomic prediction models with moderate to high predictive abilities enabled us to identify the best performing lines for higher vitamin content and the genes identified are now available for using in genomics-assisted selection breeding programs. Through this quantitative genetic analysis, we have established a key step for increasing tocochromanols in fresh sweet corn kernels, thus paving the way for the breeding of more nutritious sweet corn that can benefit human consumers.

Technical Abstract: Sweet corn (Zea mays L.), a highly consumed fresh vegetable in the United States, varies for tocochromanol (tocopherol and tocotrienol) levels but makes only a limited contribution to daily intake of vitamin E and antioxidants. We performed a genome-wide association study of six tocochromanol compounds and 14 derivative traits across a sweet corn inbred line association panel to identify genes associated with natural variation for tocochromanols and vitamin E in fresh kernels. Concordant with prior studies in mature maize kernels, an association was detected between '-tocopherol methyltransferase (vte4) and a-tocopherol content, along with tocopherol cyclase (vte1) and homogentisate geranylgeranyltransferase (hggt1) for tocotrienol variation. Additionally, two kernel starch synthesis genes, shrunken2 (sh2) and sugary1 (su1), were associated with tocotrienols, with the strongest evidence for sh2, in combination with fixed, strong vte1 and hggt1 alleles, accounting for the greater amount of tocotrienols in su1sh2 and sh2 lines. In prediction models with genome-wide markers, predictive abilities were higher for tocotrienols than tocopherols, and these models were superior to those that used marker sets targeting a priori genes involved in the biosynthesis and/or genetic control of tocochromanols. Through this quantitative genetic analysis, we have established a key step for increasing tocochromanols in fresh kernels of sweet corn for human health and nutrition.