4. Soft and hard endosperm.
Most indigenous races of maize contain soft endosperm, with the following exceptions: southeastern orange flint, Caribean yellow flint, flint races of Colombia and of Central America, northeastern little flint, and some isolated races such as Guarani white flint, Andean, Uchuquillo and Aizuma. To this one should add the various popcorn races. A study was started to determine the genetic nature of the difference of translucent from opaque kernels. So far all crosses of translucent x translucent and of opaque x opaque have bred true. The segregation between the two types, however, does not always give a monofactorial segregation, and even when the segregation was clearly monofactorial, factor interaction and dosage effects were very pronounced. Ratios vary from 3 translucent : 1 opaque to 1 translucent : 1 opaque, though segregates occur where the opaque condition appears to be dominant. Serious complications are caused by the action of genes for deep orange endosperm color, or by other closely linked genes. It may be remembered that these same color factors or genes closely linked also cause an increase in the amount of pseudostarchy kernels in orange sugary strains.
Mario P. Mezzacappa