Standard Sugary Kernel Types: The most common form of sweet corn, commonly referred to as the standard sugary (su) corn, is thought to have originated from a mutation in the Peruvian race Chullpi. Most certainly it was grown and used by Native American Indians in pro-Colombian times. In sweet corn, the sugary gene (su) prevents or retards the normal conversion of sugar into starch during endosperm development, and the kernel accumulates a water-soluble polysaccharide called 'phytoglycogen' .The higher content of water-soluble polysaccharide adds a texture quality factor in addition to sweetness. Sweet corn is eaten in the immature milk stage and is gaining importance as a popular vegetable in urban markets.

Now-a-days the standard sugary corns are being modified with other endosperm genes and gene combinations that control sweetness to develop new cultivars. At least 13 endosperm mutants, in combination with sugary, have been studied for improving sweet corn. Except for sugary, the genes used in breeding act differently to produce the taste and texture deemed desirable for sweet corn. Therefore, the growers must consider genetic type of the varieties when making selections for planting. The genetic type is not readily identifiable by cultivar name alone.

Augmented Sugary Kernel Types: In these sweet corns, the sugars are modified (increased) by the action of other genes (modifiers), either partially or completely. Major modifier genes of kernel sweetness are shrunken-2 (sh2) and sugary enhancer (se). The shrunken 2 (sh-2) sweet corn, also called supersweet, has two main advantages over the other types: 1) it is at least two to three times sweeter, and 2) the conversion of sugar to starch is negligible, thus this corn type will remain sweet up to 10 days after harvest if cooled properly followed by refrigeration. Sh-2 varieties assume tremendous market potentiality. However, problem of germination is always associated with such varieties due to lack of starch in the seed endosperm. Germination is particularly problematic when sown as kharif crop in Indian conditions. Thus such varieties should preferably be grown during rabi season to meet their demand in local market. Such corn may also be grown to catch international seed market of sh-2 corn. However, it is recommended to use such corn in combination with su corn, so that the problem of germination may be attained with little compromise with sweetness. In these partial modi¬fications, the sugary (su) kernels are modified by the segregation of major modifier genes such that about 25 percent of the kernels are double¬mutant endosperm types possessing the enhanced benefits of the modifier. The addition of the sugary enhancer (se) gene along with one of the major modifier genes like sh2 will further modify some of the sugary kernels to about 44 percent double-mutant endosperm types rather than 25 percent. In complete (100 percent) modification, the sugary (su) kernels are all modified with the sugary enhancer (se) gene to produce the double combination (su se) for obtaining maximum benefit from the su gene. Other major modifier genes of kernel sweetness are: brittle (bt), brittle-2 (bt2), and shrunken-4 (sh4). Besides these there are other genes with minor modifying effects of kernel sweetness: amyloseextender (ae), dull (du), floury (fl), floury-2 (fl2) opaque (0), opaque-2 (02), sugary-2 (su2) and waxy (wx). Many of these modifiers are known to be present in sweet corn backgrounds either in the segregating or homozygous state.