ARS | Publication request: Field release of Gibberella Zeae genetically modified to lack ascospores

Submitted to: National Fusarium Head Blight Forum Proceedings
Publication Type: Abstract
Publication Acceptance Date: October 16, 2006
Publication Date: December 5, 2006
Citation: Desjardins, A.E., Plattner, R.D., Shaner, G., Brown, D.W., Buechley, G., Proctor, R., Turgeon, B. 2006. Field release of Gibberella Zeae genetically modified to lack ascospores [abstract]. National Fusarium Head Blight Forum. p. 39.

Technical Abstract: Gibberella zeae (asexual state Fusarium graminearum) causes serious epidemics of wheat head blight worldwide, reducing seed yield and contaminating seed with trichothecene toxins. G. zeae can produce both ascospores and macroconidia during wheat head blight epidemics, but field observations have correlated epidemics with ascospore production. Previously, we generated a series of mating type (MAT)-deletion strains that lack ascospores, and MAT-complemented strains that have regained ascospore production. Here, we combined molecular and ecological approaches by conducting experiments with genetically modified strains under conditions that mimic natural epidemics. Fungal-infected pieces of maize stalk were incubated in the laboratory until ascospores developed, then placed on the ground in small plots of wheat just before and at flowering. Wild-type strains and MAT-deletion strains were applied in the first two field tests, and MAT-complemented strains were added to two additional field tests. In all field tests, genetically-modified strains were recovered from wheat seeds harvested from the treated plots. In field tests in Illinois in 2002 and Indiana in 2003, levels of wheat head blight were low in the experimental fields, as measured by seed yield reduction and trichothecene contamination. In field tests in Illinois in 2001 and 2003, however, significant wheat head blight epidemics did occur, but only in plots treated with ascospore-producing strains. This alternative approach provides new evidence that ascospores can play a critical role in epidemics in agricultural fields, at least in Illinois.