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Iturin Levels on Wheat Spikes Linked to Biological Control of Fusarium Head Blight by Bacillus amyloliquefaciens

February 2013 , Volume 103 , Number  2
Pages  146 - 155

J. M. Crane, D. M. Gibson, R. H. Vaughan, and G. C. Bergstrom

First, second, third, and fourth authors: Department of Plant Pathology and Plant-Microbe Biology, 334 Plant Science Bldg., Cornell University, Ithaca, NY 14853; and second and third authors: U.S. Department of Agriculture–Agricultural Research Service, Robert W. Holley Center for Agriculture and Health, Tower Road, Ithaca, NY 14853.

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Accepted for publication 3 October 2012.

The TrigoCor strain of Bacillus amyloliquefaciens provides consistent control against Fusarium head blight of wheat in controlled settings but there is a lack of disease and deoxynivalenol suppression in field settings. Since production of antifungal compounds is thought to be the main mode of action of TrigoCor control, we quantified levels of a key family of antifungal metabolites, iturins, as well as monitored Bacillus populations on wheat spikes over 14 days post-application in both the greenhouse and the field. We found that initial iturin levels on spikes in the greenhouse were three times greater than on spikes in the field, but that by 3 days post-application, iturin levels were equivalent and very low in both settings. We also determined that iturins declined rapidly over a 3-day post-application period on wheat spikes in both environments, despite the presence of significant Bacillus populations. Greenhouse trials and antibiosis tests indicated that the lower iturin levels on wheat spikes in the field could be a major factor limiting disease control in field settings. Future efforts to improve Bacillus disease control on wheat spikes and in the phyllosphere of various plants should focus on maintaining higher levels of iturins over critical infection periods.

This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 2013.