Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 11/5/2001
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Epidemics of Fusarium Head Blight (FHB) in the USA and Canada have been associated with Gibberella zeae colonization of crop residues. G. zeae produces sexual spores or ascospores, and asexual spores or macroconidia, but the relative importance of these two spore types in FHB is not well understood. To investigate the importance of ascospores in FHB, we deleted the mating type (MAT) locus of G. zeae strain GZ3639 to create MAT-knockout strains that cannot produce ascospores. In greenhouse tests, macroconidia from MAT-knockout strains caused FHB in inoculated wheat heads. In 2001 we compared the ability of strain GZ3639 and a MAT-knockout strain to cause FHB on wheat in a field test in Illinois. To provide inoculum, autoclaved maize stalk pieces were inoculated with fungal strains. After one month, strain GZ3639 produced abundant perithecia on the stalk pieces, while the MAT-knockout strain produced none. Stalk pieces were placed on the ground in plots of spring wheat cultivar Wheaton at 3 weeks before flowering. One plot received strain GZ3639, one received the MAT-knockout strain, and one received sterile stalk pieces. Analysis of field test data is in progress. Preliminary results indicate that the MAT-knock-out strain was significantly less effective than strain GZ3639 in reducing yield and in increasing deoxynivalenol levels of harvested seeds. This evidence confirms that ascospores can play a major role in FHB epidemics of wheat. Thus, blocking ascospore production could help disarm the virulence of G. zeae and break the cycle of FHB epidemics in wheat and other cereal grains.