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An "Ugly Duckling" of Corn Repels Borers / April 3, 2000 / News from the USDA Agricultural Research Service

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The European corn borer lays fewer eggs on the B-96 corn strain than on others.

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An "Ugly Duckling" of Corn Repels Borers

By Hank Becker
April 3, 2000 .

A misshapen corn strain could hold compounds that save corn from its worst enemy--the European corn borer.

B-96 corn is scrawny. Its stalks are weak, its roots are undeveloped and its small ears have round kernels that resemble popcorn. But B-96--a strain from Argentina--contains a chemical that other corn lines covet. It deters female European corn borers from laying eggs.

Agricultural Research Service scientists in the Corn Insects and Crop Genetics Research Unit at Ames, Iowa, focus on discovering new alternatives to chemical insecticides or Bacillus thuringiensis (Bt) bacteria--to protect corn from borers. ARS is the chief research agency of the U.S. Department of Agriculture.

Corn borers cost $350 million in losses to the nation's corn crop annually. With no preventative treatments, losses can exceed $1 billion.

Besides chemical controls, the only other practical alternative is Bt. By increasing a corn plant's natural resistance to egg-laying, scientists would help preserve the effectiveness of future generations of Bt corn. The built-in resistance would discourage egg-laying, while the Bt trait would control larvae hatching from any eggs that might be laid.

This B-96 inbred is one of thousands of corn lines preserved at the Plant Introduction Station at Ames. In lab tests, scientists discovered that it possesses a chemical protectant that interferes with borer moth egg-laying. Field testing has shown that corn borers lay relatively fewer eggs on B-96 corn, compared with susceptible lines.

Unlike susceptible corn, B-96 has a chemical defense. Scientists call this defense chemical HMBOA. The researchers have isolated and synthesized this compound and developed a laboratory bioassay to test its effectiveness. Another chemical in this family, DIMBOA, protects young corn plants from feeding borer larvae. Unlike most corn plants, B-96 plants continue producing high levels of DIMBOA and HMBOA as they mature. The scientists are studying the underlying genetic basis for the biosynthesis of these compounds, hoping to breed this trait into commercial corn--a process that could take 10 years.

Currently, scientists are looking at lines related to B-96. So far, they've found another one, called Illinois A (ILLA), that may offer even better resistance to egg-laying. But characterizing the chemical basis for ILLA resistance will require several more years of research. For more details, see the April issue of Agricultural Research.

Scientific contact: Bradley F. Binder, ARS Corn Insects and Crop Genetics Research, Ames, Iowa, phone (515) 294-6948, fax (515) 294-2265, bfbinder@iastate.edu

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