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Title: ARE GIBBERELLA ZEAE SEXUAL SPORES THE CRITICAL INOCULUM LEADING TO FHB EPIDEMICS?

Author
item Brown, Daren
item Desjardins, Anne
item YUN, SUNG-HWAN - SOONCHUNHYANG UNIV, KOREA
item Plattner, Ronald
item LEE, THERESA - SEOUL NATL UNIV, KOREA
item Dyer, Rex
item TURGEON, B - CORNELL UNIV, ITHACA, NY

Submitted to: National Fusarium Head Blight Forum
Publication Type: Abstract Only
Publication Acceptance Date: 12/10/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Gibberella zeae (anamorph Fusarium graminearum) causes Fusarium Head Blight (FHB) epidemics in wheat and barley and ear rot in corn. Fungal infections decrease yield and often contaminate grains with trichothecene mycotoxins that are harmful to human and animal health. To understand and control fungal disease, the factors and conditions that lead to epidemics must be identified. The fungal life cycle in the field can include growth on plan debris in the soil during which two types of spore may be produced: sexual spores known as ascospores and asexual spores called macroconidia. Observations in the field suggest that the sexual spores may be a primary source of inoculum for FHB epidemics. In order to test the role of sexual spores, we deleted the entire mating type locus (MAT) that controls sexual reproduction. G. zeae MAT-deletion strains appear similar to wild- type (GZ3639) in morphology and in their ability to make macroconidia but no longer make sexual spores. In greenhouse tests, macroconidia from MAT- deletion strains caused disease and produced trichothecenes following inoculation into wheat heads. To test the importance of sexual spores in disease development, we conducted a field test in Spring 2001 in which we compared the ability of GZ3639 and a MAT-deletion strain to cause FHB on on wheat. In order to focus our experiment on ascospores, we chose autoclaved corn stalk pieces as an inoculum source because GZ3639 can produce a large amount of ascospore-containing perithecia on it. We inoculated three plots (3mx3m) of Wheaton wheat, with either sterile corn stalks, corn stalks inoculated with GZ3639 or corn stalks inoculated with a MAT-deletion strain. These results suggest that new control strategies might lead to reduction of this fungus on agricultural products.