32,000 plus genes!

​At least 32000 genes in the ten chromosomes plus the independent DNA of mitochondria and chloroplasts in corn plants.  We know the function of relatively few of these genes. We have selected genetics based upon field performance for the traits that we desire for the most part but we don’t know the actual genes involved in establishing grain yield and standability. Certain physiological processes such as photosynthesis can be studies, discerning the enzymes that can be traced back to a genetic code. Based on mutations we can determine the genes involved in endosperm starch formation. Resistance to some diseases can be linked to specific genes.
 
But how about the genetics that determines number of stomata, allowing for passage of CO2 into the leaves, or loss of water.  Do genetics influence the photosynthesis in stomata guard cells determining when they open or close?  Chloroplast and mitochondria DNA influences the membrane structure of these organelles.  Replication of chloroplasts and mitochondria must involve the interactions of genetics of these organelles with that of the host cells.  Movement of minerals into cells and photosynthetic products out is partially determined by cell wall structures as influenced by genetics.  Size and number of vascular bundles must be important to movement of water from roots to leaves and ears as well as carbohydrates from leaves to roots and ears.
 
Genetics influence corn stalk rind thickness, duration of life in pith cells and carbohydrate storage capacity.  Root branching, formation of root hairs and ability to absorb water and minerals from the soil are affected by products of the corn plant’s DNA.  Kernel number and size also limited by genetics. It is no wonder that corn has a lot of genes.
 
Many of these genes had to have been established in those Teosinte plants that humans tapped several thousand years ago.  Natural occurrence of mutations and human selection of traits expressing adaptation to their environments and desires provide us with large genetic variability.  Despite modern molecular techniques to study corn DNA, the complexity of interactions within the corn plants, we are still stuck with our somewhat crude method of field testing in several environments for the best hybrids.  We do this with the knowledge that many unknown genes are influencing the final performance and the hope that there remain new genetic combinations that will lead to better performance in the future.