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Use of Molecular Markers to Create Commercially Usable Corn Inbreds and Hybrids with Low Aflatoxin in Grain


The overall objective of this research is to demonstrate that genes for resistance to Aspergillus ear rot and aflatoxin production in kernels can be moved from agronomically unacceptable resistant inbreds, such as MP313E and/or Tex6, into commercially usable inbreds and maintain the agronomic characteristics of the used inbred. <P>All of the larger multi-national corn seed companies have high throughput molecular marker genotyping programs. They will be able to use the commercially acceptable sources of resistance along with the markers described by us to improve their inbreds. Alternatively, any commercial seed company will be able to directly use the resistant lines to produce additional resistant commercial hybrids with regional adaptation by using different male parents. Many of the hybrids grown in the United States have unique male parent inbreds, many of which are proprietary property of regional seed companies. When lines are available through IFSI or Holden Foundation Seeds we will see a number of unique hybrids developed by commercial seed companies using their male parents. <P>A secondary objective is to try to determine exactly what fragments of chromosome 4 from MP313E control resistance and to create lines that only have those fragments. Others could use those lines to identify genes. Depending on funding, other sources of resistance with different chromosome regions associated with resistance can be investigated and potentially genes from different sources put into the same commercial inbreds potentially creating very high levels of resistance.

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Non-Technical Summary: The fungus Aspergillus flavus causes ear and kernel rot of corn prior to harvest. The fungus is most active under conditions of drought and high temperatures. Although the amount of kernel damage usually is very minor, the fungus produces aflatoxin as a secondary metabolite. Contamination of corn grain by aflatoxin is of major concern because of the detrimental effects on the health of animals and humans that consumed contaminated grain. Aflatoxin is a cause of primary liver cancer of humans. It also is of concern due to disruption of the marketing of grain since grain with greater than 20 ppb aflatoxin cannot be sold in interstate commerce. It can be important with ethanol production because aflatoxin is concentrated in distillers dry grains which is a byproduct of ethanol production that is often fed to cattle. Genetic resistance is the most cost-effective and reliable method of control of aflatoxin in grain. Disease resistance is farmer acceptable because it has no additional cost to them. In most situations where current hybrids have as high as 500 ng/g aflatoxin either after inoculation or in favorable natural conditions, resistant hybrids created using the resistant lines developed by this research project will have less than 200 ng/g aflatoxin. With control of certain ear feeding insects by "new Bt" events the toxin level should be much lower. In conjunction with a grain cleaner (10-15 cents/bushel) the level of aflatoxin could be reduced to <100ng/g which is very suitable for cattle feed. <P> Approach: Chromosome regions with genes for resistance from Tex6 and MP313E are being crossed into the commercially used inbred line FR1064, into a combination of B73/FR1064, and more recently into LH195RR, LH310 and LH311 (31-34). FR1064, B73, LH195RR, LH310 and LH311 are Stiff Stalk Synthetic related lines with very good agronomic characteristics. Stiff Stalk Synthetic related lines are used in a majority of corn hybrids grown in the United States. However, all Stiff Stalk Synthetic lines are highly susceptible to Aspergillus ear rot and aflatoxin production. A long term working relationship with Illinois Foundation Seeds (IFSI) allows resistance to be crossed into FR1064. IFSI's major business is the supply of foundation seeds, which makes the seed accessible to any company in the U.S. A resistant version of FR1064 would be marketed by IFSI. Due to success with backcrossing resistance into FR1064, Holden Foundation Seeds (Monsanto) is now allowing the use of LH lines. When backcrossing is complete, Holden Foundation Seeds will market the resistant lines. Therefore, resistant inbreds will be marketed by either Holden Foundation Seeds or by IFSI to any commercial seed company that wishes to purchase foundation seed.

White, Don
University of Illinois - Urbana-Champaign
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