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United States Department of Agriculture

Agricultural Research Service

Title: Reduced Virulence of Gibberella Zeae Caused by Disruption of a Trichothecene Toxin Biosynthetic Gene

Authors
item Proctor, Robert
item Hohn, Thomas
item McCormick, Susan

Submitted to: Molecular Plant-Microbe Interactions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 28, 1995
Publication Date: N/A

Interpretive Summary: The production of trichothecene mycotoxins by some species of Fusarium is thought to contribute to the ability of these fungi to cause disease. Gibberella zeae (F. graminearum) is an important pathogen of cereal crops and produces the trichothecene vomitoxin. To determine if trichothecene production contributes to the ability of G. zeae to cause disease, we generated mutants of the fungus that were unable to produce trichothecenes. The mutants that did not produce vomitoxin caused reduced disease on seedlings of the wheat variety 'Wheaton' and common winter rye, but normal disease on seedlings of 'Golden Bantam' maize. On 'Caldwell' and 'Marshall' wheat and 'Porter' oat seedlings, the mutants were inconsistent in causing less disease than the trichothecene producing strain from which they were derived. Head blight also developed more slowly on 'Wheaton' when inoculated with the mutants. These results suggest that trichothecene production contributes to the ability of G. zeae to cause disease on some hosts.

Technical Abstract: The production of trichothecene mycotoxins by some plant pathogenic species of Fusarium is thought to contribute to their virulence. Gibberella zeae (F. graminearum) is an important cereal pathogen that produces the trichothecene deoxynivalenol. To determine if trichothecene production contributes to the virulence of G. zeae, we generated trichothecene deficient mutants of the fungus by gene disruption. The disrupted gene, Tri5, encodes the enzyme trichodiene synthase, which catalyzes the first step in trichothecene biosynthesis. To disrupt Tri5, G. zeae was transformed with a plasmid carrying a doubly truncated copy of the Tri5 coding region interrupted by a hygromycin B resistance gene. Tri5- transformants were selected by screening for the inability to produce trichothecenes and by Southern blot analysis. Tri5- strains exhibited reduced virulence on seedlings of 'Wheaton' wheat and common winter rye, but wild type virulence on seedlings of 'Golden Bantam' maize. On 'Caldwell' and 'Marshall' wheat and 'Porter' oat seedlings, Tri5- strains were inconsistent in causing less disease than their wild type progenitor strain. Head blight developed more slowly on 'Wheaton' when inoculated with Tri5- mutants than when inoculated with wild type strains. These results suggest that trichothecene production contributes to the virulence of G. zeae on some hosts.

Last Modified: 4/16/2014
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