Submitted to: CIMMYT Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: October 13, 1996
Publication Date: N/A
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. Virulence was assessed under field conditions in 1994 and 1995 by controlled inoculation of G. zeae spore suspensions into flowering wheat heads. Trichothecene-nonproducing (Tri5-) mutants were less virulent than 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.