Submitted to: Molecular Plant Microbe Interactions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/1996
Publication Date: N/A
Citation: Interpretive Summary: Certain fungi can cause serious epidemics of head scab on wheat, barley and other small grains. These fungi reduce yield and produce toxins that contaminate grain and make it unsuitable for animal feed and human food. We have tested toxin-nonproducing fungi and shown that they are greatly reduced in their ability to cause head scab on wheat grown in the field. These results suggest new approaches for controlling scab.
Technical Abstract: We have analyzed the role of trichothecene antibiotics in the virulence of the fungus Gibberella zeae (anamorph, Fusarium graminearum) on wheat (Triticum aestivum). Trichothecene nonproducing mutants of G. zeae were obtained by disrupting Tri5, the gene encoding trichodiene synthase, which catalyzes the first committed step in the trichothecene biosynthetic pathway. Trichothecene-nonproducing mutants appear to be normal in growth and development under laboratory conditions. One such mutant was selfed to generate a meiotic revertant that lost the disruption vector and recovered trichothecene production. In the present study, virulence was assessed in 1994 and 1995 by controlled field inoculation of G. zeae spore suspensions into flowering wheat heads. Trichothecene nonproducing (Tri5-) mutants were less virulent than the trichothecene-producing (Tri5+) parental and revertant strains in their ability to cause head scab on field-grown wheat. Although trichothecene-nonproducing strains colonized wheat heads, the infected heads showed less disease by several parameters we tested, including head bleaching symptoms, seed weight, seed viability, and trichothecene contamination. This evidence indicates that trichothecene antibiotics are virulence factors in wheat head scab.