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origin of supersweet corn?

W.F. Tracy wftracy at facstaff.wisc.edu
Mon Aug 24 08:32:42 EST 1998

Origin of Supersweet Sweet Corn.

	In the early 1950s, John R. Laughnan was studying alleles at the
anthocyanin1 (A1) locus.  To aid in these studies he obtained a stock from
E.B. Mains of the University of Michigan, in which the recessive allele a1
was very tightly linked to a newly described gene, sh2 (Mains 1948;
Laughnan 1953, 1954).  In the course of these studies on the a1 locus
Laughnan (1953) noted that the kernels of sh2 are unusually sweet and have
a pleasant malty flavor.  He then carried out extensive studies on the
biochemical effects of sh2 relative to both su1 and normal on endosperm
carbohydrates.  Among his conclusions were the following sh2 endosperms
store less starch than normal and su1 endosperms but in regard to sugars,
exhibit approximately  ten-fold and four-fold increases over normal and
sugary types respectively; most of this is due to sucrose....  Laughnan
also noted that the double recessive su1sh2 resulted in even more sugar and
less starch.  He correctly predicted that the su1 gene acts after sh2  in
starch biosynthesis.  He also suggested that sh2 would be desirable for the
sweet corn industry because of its initially higher sugar content and
expected longer shelf life.

	To alert sweet corn researchers, Laughnan then published a brief
report in the trade magazine The Canner (Laughnan 1954).  In this article
he discussed the advantages of higher sugar and longer shelf life, plus the
very favorable taste test results.  We now know Laughnan was correct on
these predictions.  However, in The Canner article, he was mistaken on one
important point.  He stated it is reassuring that representatives of a
considerable number of experiment stations and private companies have
expressed their enthusiasm over the possibilities which this new finding
offers.  Soon they will be actively engaged in introducing the new shrunken
factor into preferred sweet lines. Whether the people Laughnan mentioned,
never started a program on sh2 or started and became discouraged due to
poor seed quality and vigor, it was soon clear to Laughnan very few would
make a sustained effort.

	Laughnan as a research geneticist in the Department of Botany at
the University of Illinois could have been expected to discontinue this
work at that point.  He had done the underlying science, alerted the
industry and other researchers to the exciting possibilities, and made his
stocks freely available.  Furthermore no funding for this type of research
was available, and he had major teaching and research responsibilities.
But, like many pioneers he saw opportunities where others did not, and
perhaps overlooked pitfalls that others saw as unbreachable.  Laughnan
began a breeding program of his own.   He backcrossed the sh2 allele into a
number of established sugary inbreds, including P39, P51, Ia453, and
Ia5125.  The su1 version of P39 X P51 was the famous hybrid `Golden Cross
Bantam and Ia453 X Ia5125 made the popular hybrid `Iochief'.  After a
suitable number of backcrosses, Laughnan had to create enough hybrid seed
for evaluation.  Since no financial support for this work was available, he
planted hybrid seed production blocks on rented land and he and his sons
maintained these plots including detasseling the seed parent.  He than
offered the hybrid seed to home gardeners who received it enthusiastically
and was able to have some canned and frozen (Laughnan 1961).  In the 13
January 1961 issue of Seed World he announced the release of the Super
Sweet counterparts of `Golden Cross' and `Iochief' hybrids  and said
samples would be available for the 1961 planting season from Illinois
Foundation Seeds Co (IFS) (Laughnan 1961).  The supersweet `Iochief' became
known as `Illini Chief'. The seed of `Illini Chief' was difficult to
produce and a three-way hybrid, (Ia453sh2 X P39sh2) X Ia5125sh2 was
developed with improved seed production capability.  This hybrid was named
`Illini Xtra Sweet' and is still sold today.  Thus in fewer than eight
years from his original suggestion Laughnan had developed a commercially
acceptable hybrid, while fulfilling his other responsibilities.

>From History, Genetics, and Breeding of Supersweet (shrunken2) Sweet
Corn"  W. F. Tracy. Plant Breeding Reviews 14 :189-236

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