Agriculture Reference
In-Depth Information
three main families, or genotypes, of the new varieties, each with its own set of attributes.
Agronomists refer to them by a twoletter shorthand.
The oldest improved variety is "su," for "sugary." This kind of sweet corn started being
mentioned in seed journals in the 1820s but had probably existed before - the result of
farmers selecting seed from the sweetest plants to propagate the next year. Most varieties
of this type of corn have a sugar content ranging from 10 to 15 percent. That sugar starts
converting to starch the moment the corn is picked. If left at room temperature, an ear of
"su" corn will lose half of its sugar in less than a day. Even if chilled to normal refrigerator
temperatures, it will lose two thirds of its sweetness within three days.
The next advance was a variety called "se," for "sugar-enhanced." This kind of corn is
a lot sweeter than normal corn, containing as much as twice the sugar. The sugar-to-starch
conversion occurs at about the same rate as for traditional corn, but because "se" corn
starts out so much sweeter, it takes up to a week of storage before it falls to the sweetness
level of normal corn.
The King Kongs of the corn world are varieties that are not only supersweet but that
also go starchy much more slowly. These are called "sh2" corns because of the way their
kernels shrivel and appear shrunken after drying. These varieties contain sugar levels
between 30 and 45 percent - two to three times that of traditional corn. And their sugar-to-
starch conversion rate is so slow as to be almost nonexistent. Even after being stored for
a couple of days at warm room temperature (80 degrees), these varieties still have more
than twice as much sugar as a freshly picked normal ear. They have been slow to win ac-
ceptance because the seed is significantly more expensive than that for the other improved
corn types, and shoppers have been reluctant to pay the extra money.
Supersweet corn is the result of traditional plant breeding spurred by naturally occur-
ring genetic mutations. Think of this breeding in terms of basketball players. In the gen-
eral population, the occurrence of extremely tall humans is rare. But if two extremely tall
people should find each other, fall in love and have children, the odds that their offspring
will be extremely tall are, well, pretty short. And so it is with corn. Once breeders started
working with a few "freak" corn plants that produced ears with very sweet kernels, it was
just a matter of breeding and crossbreeding a few dozen generations to get where we are
today.
The first real work on these supersweet corns was done by a University of Illinois pro-
fessor named John Laughnan in the 1950s. But these varieties didn't catch on until the
mid-1980s, and then they caught on quickly. In Florida, a prime winter corn-growing state,
