Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/31/2008
Publication Date: 7/9/2008
Citation: Desjardins, A.E., Busman, M., Manandhar, G., Jarosz, A.M., Manandhar, H.K., Proctor, R. 2008. Gibberella Ear Rot of Maize (Zea mays) in Nepal: Distribution of the Mycotoxins Nivalenol and Deoxynivalenol in Naturally and Experimentally Infected Maize. Journal of Agricultural and Food Chemistry. 56(13):5428-5436. Interpretive Summary: The fungus Fusarium graminearum causes ear rot of maize and contaminates the grain with mycotoxins. Fusarium graminearum strains from the United States produce the mycotoxin deoxynivalenol (DON) only, but strains from Nepal produce both DON and the closely-related mycotoxin nivalenol (NIV), which is more toxic to animals. Our study of fungal strains from the United States and Nepal showed that DON-producers cause more maize ear rot than do NIV-producers. These data indicate that production of DON rather than NIV confers a selective advantage to this important maize pathogen, and help explain why strains that produce the less toxic DON predominate on maize in the United States.
Technical Abstract: The fungus Fusarium graminearum (sexual stage Gibberella zeae) causes ear rot of maize (Zea mays) and contamination with the 8-ketotrichothecenes nivalenol (NIV) or 4-deoxynivalenol (DON), depending on diversity of the fungal population for the 4-oxygenase gene (TRI13). To determine the importance of NIV and DON in maize ear rot, we combined a survey of naturally contaminated maize in Nepal with experiments in the field and in a plant growth room. In the survey, NIV contamination was 4-fold more frequent than DON contamination and NIV-producers (TRI13) were isolated more than twice as frequently as DON-producers ('TRI13). In maize ear rot experiments, genetically diverse NIV-producers and DON-producers caused ear rot and trichothecene contamination. Among strains with the same genetic background, however, NIV-producers caused less ear rot and trichothecene contamination than did DON-producers. The high frequency of NIV contamination and the high virulence of many NIV-producers are of concern because maize is a staple food of rural populations in Nepal and because NIV has proven more toxic than DON to animals.