|Stockwell, V. - OSU|
|Johnson, K - OSU|
Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: September 17, 1999
Publication Date: N/A
Technical Abstract: Mixtures of antagonists can enhance disease control compared to single inoculants providing strains are ecologically compatible. Combining Pseudomonas fluorescens A506 with strains of Pantoea agglomerans often results in greater population sizes of the antagonists on blossoms, but control is not enhanced compared to single strains. We propose that mechanistic incompatibility, whereby a member of a mixture interferes with the mode-of-action of its co-inoculant, compromises the efficacy of our mixture. Herbicolins or microcins produced by P. agglomerans 252 were important in control of fire blight on pear blossoms in a 1998 field trial. Pa252 reduced disease incidence by 72 percent, whereas a non-antibiotic producing mutant did not provide significant control compared to water-treated trees. In cultural assays, PfA506 detoxified antibiotics produced by Pa252, presumably by the production of extracellular protease (Ecp). We have obtained an Ecp- mutant of PfA506 and will evaluate its ecological and mechanistic compatibility with Pa252 in field trials on biological control of fire blight of pear.