Genetic analysis of visually scored orange kernel color in maize

Authors: CHANDLER, KRISTIN - Purdue University; Lipka, Alexander; OWENS, BRENDA - Purdue University; LI, HUIHUI - Chinese Academy Of Agricultural Sciences; Buckler, Edward - Ed; ROCHEFORD, TORBERT - Purdue University; Gore, Michael

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/16/2012
Publication Date: 11/26/2012
Citation: Chandler, K., Lipka, A.E., Owens, B.F., Li, H., Buckler IV, E.S., Rocheford, T., Gore, M.A. 2012. Genetic analysis of visually scored orange kernel color in maize. Crop Science. 53:189-200.

Interpretive Summary: Carotenoids are a group of pigments found in many plants, some of which exhibit provitamin A activity. Because provitamin A is converted to vitamin A when eaten by humans, increasing the amount of carotenoids in food sources through plant breeding, or biofortification, is a sustainable approach to reduce the prevalence of vitamin A deficiency (VAD). In many regions of Africa where VAD is common, white maize grain, which contains little to no carotenoids, is preferred to yellow maize grain, which contains carotenoids. Currently, there are efforts to introduce orange maize grain, which is positively correlated with total carotenoid content and uncommon to Africa. To gain a better understanding of the genetics underlying orange grain color, we conducted a genetic analysis in a maize population by visually scoring grain color ranging from light yellow to dark orange. Our analysis showed that six carotenoid biosynthetic genes are associated with orange grain color. Thus, our study suggests that selection for orange endosperm color in maize provitamin A biofortification breeding programs could be done visually or through molecular markers associated with carotenoid biosynthetic genes.

Technical Abstract: Increasing levels of provitamin A carotenoids in maize (Zea mays L.) grain through plant breeding, termed biofortification, is an economical and sustainable way to help humans suffering from vitamin A deficiency (VAD). Unfortunately, in parts of Africa where VAD is prevalent, there is frequently a consumer preference for maize grain with white endosperm, which has little or no carotenoids, and consumer avoidance of maize grain with yellow endosperm that has carotenoids. Consequently, there is an effort to introduce orange maize grain, uncommon in Africa, containing a high level of carotenoids. This study assessed whether chromosomal loci could be associated with visual scores for relative intensity of orange endosperm color. Linkage analysis across and within ten families of the maize Nested Association Mapping population identified five common quantitative trait loci (QTL), and six rare QTL for orange endosperm color. Most QTL coincide with carotenoid biosynthetic pathway genes. We discovered an association between multiple alleles of y1 and orange endosperm color. This novel finding shows that y1 is involved in more than only the conversion of white to yellow endosperm. Our results indicate that selection for orange endosperm color could be done visually or through markers associated with carotenoid biosynthetic genes. Such selection can also be easily combined with ongoing marker-assisted selection efforts to produce higher provitamin A levels in maize grain.