CONTROL OF FUSARIUM MYCOTOXINS IN CORN, WHEAT, AND BARLEY
Location: Bacterial Foodborne Pathogens & Mycology Research Unit
Title: The TRI101 Story: Engineering Wheat and Barley to Resist Fusarium Head Blight
Submitted to: World Mycotoxin Forum, the Third Conference
Publication Type: Abstract Only
Publication Acceptance Date: November 6, 2006
Publication Date: November 6, 2006
Citation: Alexander, N.J., Blechl, A.E., Okubara, P.A., Mc Cormick, S.P., Manoharan, M., Dahleen, L.S., Kendra, D.F. 2006. The TRI101 Story: Engineering Wheat and Barley to Resist Fusarium Head Blight [abstract]. World Mycotoxin Forum, the Fourth Conference. p. 123.
Fusarium Head Blight (FHB), caused primarily by Fusarium graminearum, is a major disease of wheat and barley in the United States and Canada. The disease process depends on high humidity and the presence of inoculum (fungal spores), and therefore, the amount of disease can vary from year to year with the amount and timing of rainfall. FHB epidemics have been on the increase since 1993 and have caused severe monetary damage to the growers and to the seed industry. Infection of wheat and barley by F. graminearum causes necrosis of the florets that gives the head a "scabby" appearance, and results in moderate to severe reduction in grain yields.
Along with the reduced yields, the presence of mycotoxins in the moldy grain constitutes a major problem for the grain industry. The fungus produces trichothecenes as it grows throughout the plant tissue. These mycotoxins pose health problems to humans and non-ruminant animals upon ingestion. As a result, governmental agencies, both in the U.S. and Europe, have imposed limits on the amounts of deoxynivalenol (DON), the primary trichothecene produced by F. graminearum, that are acceptable in grain. Cultivars of wheat and barley that are resistant to F. graminearum are needed.
The fungus is able to protect itself from trichothecenes by modifying the core trichothecene as soon as it is biosynthetically formed. The gene responsible for this modification, Tri101, encodes a trichothecene acetyltransferase. The modified trichothecene has been shown to be less toxic to plants. DON is also involved with virulence in wheat, as lines of non-toxin producing F. graminearum do not cause much disease. Utilizing this information, our laboratories investigated the novel strategy of introducing the fungal gene, FsTri101, into wheat and barley. The extra FsTRI101 activity was expected to limit the accumulation of DON in the plant as well as limit the spread of disease within the plant.
Fusarium-susceptible lines of wheat (Bobwhite) and barley (Conlon) were transformed with FsTri101 constructs. Proof was obtained for the presence and expression of the gene in the transformants. Greenhouse tests showed that transgenic lines of both wheat and barley had a reduction in FHB symptoms. Barley transgenics showed a reduced accumulation of DON. These results demonstrated, for the first time, that FHB severity and DON accumulation can be reduced in wheat and barley by the introduction of a toxin-modification gene.