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Photo: A microbiologist examines a fungal culture. Link to photo information
Microbiologist Don Wicklow examines a culture of Acremonium zeae. Cultures of A. zeae isolates from corn can be seen on the computer screen. Click the image for more information about it.

Scientists Tap Fungus to Protect Corn

By Jan Suszkiw
December 9, 2004

A benign fungus that lives inside corn may yield new clues to protecting the crop from contamination by the molds Aspergillus flavus and Fusarium verticillioides, according to Agricultural Research Service (ARS) microbiologist Don Wicklow.

Wicklow teamed up with University of Iowa scientist Jim Gloer to discover that the fungus endophyte Acremonium zeae produces substances called pyrrocidines that disrupt the Aspergillus and Fusarium molds’ ability to infect ripening corn kernels. Wicklow works at ARS’ National Center for Agricultural Utilization Research in Peoria, Ill.

Besides causing diseases in the corn crop, the molds can contaminate it with natural carcinogens called mycotoxins that can be harmful to both humans and livestock. Mycotoxin-related losses, such as devalued markets, rejected harvests and testing fees, cost the U.S. corn industry hundreds of millions of dollars annually.

According to Wicklow, A. zeae’sproduction of pyrrocidines challenges decades-old scientific thinking that the endophyte is an inert player in the world of corn-fungal interactions, neither harming nor benefiting its host. Now, it appears the endophyte “pays” for its room and board in corn by fending off the molds. The finding warrants taking a closer look at the field conditions under which this rivalry occurs and exploiting it, perhaps using cultural methods that favor the endophyte. Further research may reveal another possible approach: inoculating corn seed with the endophyte as a kind of living barrier against A. flavus and F. verticillioides.

So far, Wicklow and Gloer have isolated the pyrrocidines from 13 different cultures of the endophyte. Wicklow also conducted field studies to make sure their lab-based observations of A. zeae's antifungal activity weren’t the result of a natural corn defense or the byproduct of human error. According to Wicklow, at the ARS center’s Mycotoxin Research Unit, the pyrrocidines also stymie certain bacteria, and are the first-known natural products to be isolated from the endophyte.

Read more about the research in the December issue of Agricultural Research magazine.

ARS is the U.S. Department of Agriculture's chief scientific research agency.