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ultraviolet light to induce mutations, microbiologists Charles Bacon and
Dorothy Hinton screen petri dishes of Bacillus mojavensis bacteria for
growth on media amended with fusaric acid. Growth on such media reflects
resistance to fusaric acid. Click the image for more information about
Fighting Crop-Damaging Fungi With Bacteria
Durham October 2, 2006
"Bacillus Meets Fusarium" may sound like a monster movie
title, but to Agricultural Research Service (ARS) microbiologist and research leader
Bacon, it's shaping up to be a good battle.
Researchers in the ARS
and Mycotoxin Research Unit at Athens, Ga., have found a bacterium that can
greatly reduce the colonization of corn by Fusarium verticillioides.
That's a good thing, because this is a toxin-producing strain of
Fusarium fungus that can reduce the marketability of crops infected with
F. verticillioides is an endophyte in cornthat is, it
takes up residence inside the corn. Sometimes such plant inhabitants can be
beneficial, but F. verticillioides clearly is not. So Bacon and
Hinton went hunting for some "good" endophytic microbes that might squeeze
the hostile fungus out.
Enter Bacillus mojavensis, a bacterial endophyte with
plant-enhancing traits. Bacon and Hinton found that this bacterium, already
patented by ARS to protect plants from disease, greatly reduces the amount of
fungus in corn. It can naturally "infect" corn seedlings from a one-time
application to seed and persist throughout the corn's growth and development.
Greenhouse trials conducted by Bacon and Hinton showed that B.
mojavensis achieves up to a 70-percent reduction in fumonisin mycotoxin.
Unfortunately, they found that when F. verticillioides is stressed, it
produces fusaric acid, which is toxic to the bacterium.
For two years, Bacon and Hinton searched for a mutant bacterial strain
resistant to fusaric acid, but still capable of controlling the fungus. They
found two strains that they say provide the biocontrol tools needed for
more-effective field studies in corn and wheat.
Discovering that B. mojavensis forms natural endophytic
associations with a wide range of plants is expected to influence the basic
approach of using bacterial endophytes as a biocontrol strategy for protecting
all plants. The approach offers many advantages over traditional biocontrol
bacteria because endophytes are systemic and persist as long as the plant host
about this and other food safety research in the October 2006 issue of
Agricultural Research magazine.
ARS is the U.S. Department of
Agriculture's chief scientific research agency.