Articles
ESTABLISHMENT OF FREEZE-DRIED BACTERIA ON PEAR AND APPLE BLOSSOMS
Article number
411_58
Pages
295 – 296
Language
Abstract
The influence of inoculum preparation on the establishment of bacterial antagonists that suppress fire blight on blossoms was evaluated.
Aqueous suspensions (108 cfu/ml) of Pseudomonas fluorescens A506 or Erwinia herbicola C9-1 were prepared from cells scraped directly from the surface of nutrient agar plus 1% glycerol or cells that were freeze-dried after growth under similar culture conditions.
Cell suspensions were sprayed on pear and apple trees in 50% bloom at mid-day and populations of A506 and C9–1 on stigmas of individual blossoms were followed over several days.
Fluorescent microspheres (1 μm, yellow- green-colored carboxylate microspheres, Polysciences, Inc., Warrington, PA, USA) were added to sprays at a concentration of 107 spheres/ml to provide a method to mark flowers that were open during spray inoculation.
After blossom samples were dilution plated to estimate the population size of a bacterial antagonist, the stigmas and styles of each blossom were examined for the presence of microspheres with a fluorescence microscope (485 nm excitation, 520 nm emission filter). In most trials, A506 and C9-1 applied either as cells harvested from media or as freeze-dried cells eventually achieved similar populations of 105 cfu/blossom.
A506 and C9-1 were often recovered from a greater proportion of blossoms if the inocula consisted of freeze-dried cells rather than cells harvested directly from solid media.
All blossoms harvested within four days after spraying had microspheres present on the surfaces of the styles and stigmas; thus, all of the blossoms sampled were inoculated directly and the lack of recovery of antagonists from blossoms was due to their inability to establish detectable populations rather than the escape of some blossoms from treatment.
The use of freeze-dried cells in field trials decreased variability in the incidence of establishment of bacterial antagonists on blossoms.
Aqueous suspensions (108 cfu/ml) of Pseudomonas fluorescens A506 or Erwinia herbicola C9-1 were prepared from cells scraped directly from the surface of nutrient agar plus 1% glycerol or cells that were freeze-dried after growth under similar culture conditions.
Cell suspensions were sprayed on pear and apple trees in 50% bloom at mid-day and populations of A506 and C9–1 on stigmas of individual blossoms were followed over several days.
Fluorescent microspheres (1 μm, yellow- green-colored carboxylate microspheres, Polysciences, Inc., Warrington, PA, USA) were added to sprays at a concentration of 107 spheres/ml to provide a method to mark flowers that were open during spray inoculation.
After blossom samples were dilution plated to estimate the population size of a bacterial antagonist, the stigmas and styles of each blossom were examined for the presence of microspheres with a fluorescence microscope (485 nm excitation, 520 nm emission filter). In most trials, A506 and C9-1 applied either as cells harvested from media or as freeze-dried cells eventually achieved similar populations of 105 cfu/blossom.
A506 and C9-1 were often recovered from a greater proportion of blossoms if the inocula consisted of freeze-dried cells rather than cells harvested directly from solid media.
All blossoms harvested within four days after spraying had microspheres present on the surfaces of the styles and stigmas; thus, all of the blossoms sampled were inoculated directly and the lack of recovery of antagonists from blossoms was due to their inability to establish detectable populations rather than the escape of some blossoms from treatment.
The use of freeze-dried cells in field trials decreased variability in the incidence of establishment of bacterial antagonists on blossoms.
Publication
Authors
V.O. Stockwell, J.E. Loper, K.B. Johnson
Keywords
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