We generally think of corn genetic differences as expressed in grain yield and grain characteristics. However, genetics unique to each hybrid influences its reaction to environmental as well as appearance through out the season. Nuclear genes in each cell plus the independent genetics of some cell organelle such as mitochondria and chloroplasts are being expressed in the reactions to environments as well.
Basic gene function must be effective in all living corn plants except in those few with major mutations. Corn breeders attempt to select individuals that have the characteristics, and thus, the genetics, preferred by the ultimate use of the hybrid. Unseen gene products carry out most physiological functions without our intentional interference. Thousands of genes are regulated and activated for the growth and function of all corn plants without our direct genetic intervention. We do, however, attempt to select those relatively few genes that affect the products most desired by the user of corn. Each of these traits are inherited by relatively few genes.
We can select for flowering timing, relative ear and plant height, grain quality characteristics from the variability present within a breeding population. Resistance to each potential corn disease usually only involves 3-4 genes available in some genetic source within corn. Grain quality characteristics are mostly affected by only a few genes. The challenge is to select for these relatively simple inherited characteristics within the background of those other physiological and morphological functions influence by those thousands of other genes. Furthermore, the expression of those genes must be relative to the varied environments faced by the growing crops.
Added to this breeding difficulty, we must stabilize the genetics by selfing to make inbreds and then match inbreds to make a hybrid combination for repeatable performance in the field. It is no surprise to find appearance differences among hybrids within a variety display plot. Each hybrid exhibited desirable product performance to be commercialized. Each got there by slightly different genetic pathways and because of the necessity of having homozygous parents, each plant within a hybrid will appear identical to each other but different from the other hybrids. Characters such as shape of canopy, length of leaves, and color and shape of tassel are inherited and uniform within a single cross hybrid as the result of uniform homozygosity of the hybrid parents.
Homozygosity of hybrid parents results in uniform and identical genetics for each plant of the hybrid. This applies to each morphological character when the plants are grown in a uniform environment. This applies to corn seedlings as well. PSR has utilized this concept for 33 years assisting seed companies in assuring seed genetic purity of each lot of new seed production. Genetics affect all function and appearance of corn at all development stages.
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.