Increasing consumer demand for natural ingredients in foods and beverages justifies investigations into more economic sources of natural colorants. In this study, 398 genetically diverse pigmented accessions of maize were analyzed using HPLC to characterize the diversity of anthocyanin composition and concentration in maize germplasm. One hundred and sixty-seven accessions were identified that could produce anthocyanins in the kernel pericarp or aleurone and were classified into compositional categories. Anthocyanin content was highest in pericarp-pigmented accessions with flavanol-anthocyanin condensed forms, similar to the Andean Maı́z Morado landraces. A selected subset of accessions exhibited high broad-sense heritability estimates for anthocyanin production, indicating this trait can be manipulated through breeding. This study represents the most comprehensive screening of pigmented maize lines to date and will provide information to plant breeders looking to develop anthocyanin-rich maize hybrids as an economic source of natural colorants in foods and beverages.

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The reduced acylation phenotype describes the inability of certain accessions of maize (Zea mays [L.]) to produce significant amounts of acylated anthocyanins, which are typically the most abundant pigments. Acylated anthocyanins are important for their association with stability and are therefore important for the various industries using anthocyanins as natural colorants to replace synthetic dyes. Many anthocyanin acyltransferases have been characterized in other species; however, no anthocyanin acyltransferases have been characterized in maize. Therefore, a mapping population was developed from a cross between mutant stock 707G and wild-type acylation line B73 to identify the locus associated with the reduced acylation trait. High-performance liquid chromatography was used to assay the pigment content and composition of 129 F2 lines generated in the mapping population. Recessive alleles of Colorless1, Colored1, and the reduced acylation mutant all decreased anthocyanin content while Intensifier1 increased anthocyanin content in aleurone tissue. The association of increased proportions of acylation with increased anthocyanin content indicates acylation may be important for increasing the stability of anthocyanins in vivo. Genotyping-by-sequencing was used to create SNP markers to map the reduced acylation locus. In the QTL analysis, a segment of Chromosome 1 containing transferase family protein GRMZM2G387394 was found to be significant. A UniformMu Mu transposon knockout of GRMZM2G387394 demonstrated this gene has anthocyanidin malonyltransferase activity and will therefore be named Anthocyanin Acyltransferase1 (AAT1). AAT1 is the first anthocyanin acyltransferase characterized in a monocot species and will increase our knowledge of all acyltransferase family members.

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