The colors of corn grain are basically purple, red, yellow and white. Each pigment is produced through a series of metabolic processes. Purple and red pigments are due to production of anthocyanin whereas yellow is a carotenoid and white is absent of all of these. Anthocyanin is a flavonoid compound that is produced in an aleurone cells of the endosperm. Carotenoids, the yellow color, is produced in the starchy cells in the center of the endosperm.
A few genes of more than 20 involved in anthocyanin pigment production have major effects on anthocyanin as they are responsible for production of enzymes needed for the one of the steps in producing the pigment. If the dominant gene Pr1 is present, a purple aleurone is the result. If the recessive version of this gene (pr1), a red colored aleurone will be present. However, another gene (C1), active in the kernel aleurone cells, functions as a promotor gene encoding for a protein that allows the production of the anthocyanin molecules. A mutant of the C1 gene does not allow to produce the anthocyanin production and thus no purple or red color. Another gene (R1), also is needed for the anthocyanin production and the recessive version (r1), blocks the pigment formation.
Carotenes, affected by the Y1 gene are produced in the starchy cells of the endosperm. Carotenes are responsible for the yellow color of the endosperm. The homozygous recessive version of (y1) gives a white starchy endosperm
Colorless aleurone combined with the recessive y1 will result in all white kernels. Genetics of the endosperm is not simple because it includes two sets of genes from the seed parent and one from the pollen parent. White kernels require recessive c1c1c1 in the aleurone cells of the endosperm and y1y1y1 in the starchy cells of the endosperm. Yellow flint and yellow dent corn has recessive c1c1c1 and Y1Y1Y1 genes. It amazes me that people had already sorted out these types, without knowing genetics, before the Europeans arrived in the new world to see corn for the first time.
About Corn Journal
The purpose of this blog is to share perspectives of the biology of corn, its seed and diseases in a mix of technical and not so technical terms with all who are interested in this major crop. With more technical references to any of the topics easily available on the web with a search of key words, the blog will rarely cite references but will attempt to be accurate. Comments are welcome but will be screened before publishing. Comments and questions directed to the author by emails are encouraged.