Jeffrey D. Palumbo,
Teresa L. O'Keeffe,
Hamed K. Abbas, and
Bobbie J. Johnson
First, second, and third authors: U.S. Department of Agriculture-Agricultural Research Service (USDA-ARS), Plant Mycotoxin Research Unit, Albany CA 94710; and fourth and fifth authors: USDA-ARS, Crop Genetics and Production Research Unit, Stoneville, MS 38776.
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Accepted for publication 26 January 2010.
Pseudomonas chlororaphis strain JP1015 and P. fluorescens strain JP2175 were previously isolated from Mississippi cornfield soil samples and selected for their growth inhibition of Aspergillus flavus in laboratory culture. In this study, the antifungal activity of these bacterial strains against A. flavus in soil coculture was determined. Growth of A. flavus was inhibited up to 100-fold by P. chlororaphis strain JP1015 and up to 58-fold by P. fluorescens strain JP2175 within 3 days following soil coinoculation. A. flavus propagule densities after 16 days remained 7- to 20-fold lower in soil treated with either bacterial strain. Using a bench-scale wind chamber, we demonstrated that treatments of soil with P. chlororaphis strain JP1015 and P. fluorescens strain JP2175 reduced airborne spores dispersed across a 1 m distance by 75- to 1,000-fold and 10- to 50-fold, respectively, depending on soil type and inoculum level. These results suggest that application of these bacterial strains may be effective in reducing soil populations of mycotoxigenic fungi, thereby reducing fungal spore formation, and ultimately reducing the potential for crop plant infection via airborne transmission.
Additional keywords:maize (Zea mays), rhizosphere.
The American Phytopathological Society, 2010