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Sweet Corn: Breeding for Diversity

Summary

There are four main races of corn. About 70% of the genetics of sweet corn is derived from the Northern Flint race. The purpose if this paper is to document my plan for increasing the genetic diversity of my sweet corn by introducing genetics from other corn races.
Northern Flint Race
The Northern Flint race of corn is overly represented in my sweet corn. It contains low genetic diversity. The genetic background of popcorn contains many unique alleles and consists of approximately ½ Northern Flint, ¼ Tropical Lowland, and ¼ Southern Dent. A popcorn land-race should be crossed with a short season sweet corn and incorporated into the sweet corn population after segregation. This cross may also be used to decrease the days-to-maturity of my popcorn.
Andean Race
The Andean race of corn contains low genetic diversity, but it moved south from Mexico during the maize diaspora so it may contain genetic material not found in the Northern Flint race. Peruvian Purple flour corn should be crossed with sugary enhanced sweet corn. This should be allowed to segregate, and should also be back-crossed using the Peruvian corn as the recurrent parent. The seeds of this cross taste like cherries. Giant Mexican Helote seed is available. It should be crossed with sweet corn. If other Andean races can be obtained they should be crossed and segregated.
Tropical Lowland Race
The Tropical lowland race consists of the Southern Dents. A cross between Earthtones Dent and sugary enhanced sweet corn was made in 2010. A cross was also made with an unnamed dent. These were segregated in 2011 and incorporated into the sweet corn population. In 2011 a cross between Cherokee Squaw and Silver King was segregated. It is too long season for my garden, so it should be crossed with a shorter season corn. No back-crosses are contemplated.
Mexican Highland Race
The Mexican Highland Race is the most diverse race of maize. The other races are descended from this race which is thought to have originated near Oacaxa Mexico. The range of the Mexican Highland race extends northward through Hopiland. In 2010 three Hopi corns were crossed with sweet corn. In 2011 these were segregated. In 2012 they are being grown out for evaluation and incorporation into the sweetcorn landrace. A sample of corn from Oaxaca was grown in 2010. It had day-length or days-to-maturity issues and the attempt to cross it with sweet corn was not successful, though the seed was increased. In 2011 an attempted cross did not mature before it was killed by a hard frost. In 2012 the seed was planted on the East side of a building which may shorten the effective daylength and allow hand pollination with a very short season sweet corn. Posole, and Oaxacan Green corn may contain Highland genes and should be incorporated into the program. Maricopa sweet, and wild teosinte should be grown out to increase seed before incorporation into the program. A hybrid swarm of Zea mays should be maintained as a source of new pheotypes. The Mexican Highland race should be well represented in the swarm.

Warm Regards,
Joseph
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