Articles
SURVIVAL OF PANTOEA AGGLOMERANS E325 AS FIRE BLIGHT BIOCONTROL AGENT WHEN OSMOADAPTED IN HIGH-SALINE MEDIUM
Article number
896_68
Pages
467 – 470
Language
English
Abstract
Pantoea agglomerans E325 is a commercially available biocontrol agent for fire blight in the USA. Osmoadaptation, involving the combination of saline osmotic stress and osmolyte amendment to growth media, was investigated as a means of improving the survival of E325 on apple and pear blossoms under dry western conditions.
Two complex media, nutrient yeast dextrose broth and the commercial fermentation medium, were supplemented with 0.5 M NaCl and 0.1 mM glycine betaine according to Bonaterra et al. (2005, 2007). E325 was cultured at ARS-USDA laboratory and commercial facility, then freeze dried with cryoprotectants and applied to Gala apple blossoms in an orchard.
In 2009, initial population sizes on blossom stigmas, and areas under population-size curves (Aps), were greater for osmoadapted than non-osmoadapted E325. However, comparison of treatments based on areas under the daily-growth curves (Adg) indicated no differences.
Results were confirmed by a second trial in 2010. This led us to examine the stability of the E325 preparations prior to field application.
Preparations used for field tests continued to be maintained at -20°C and were sampled periodically to estimate viable concentrations.
Separate stability tests were also performed involving osmoadapted E325 with and without cryoprotectants.
Additionally, we evaluated survival and growth of osmoadapted E325 on both the stigmas and hypanthia of detached crab apple blossoms.
Osmoadaptation improved the survival of E325 during freeze drying and subsequent storage prior to application, but did not eliminate the need for cryoprotectants.
This production method, however, did not increase the survival of E325 on blossom stigmas under low relative humidity in the orchard (45% average) or laboratory (50 or 70%), but was shown in the laboratory to increase survival and growth in the blossom hypanthium.
Further orchard experimentation is necessary to verify this.
Two complex media, nutrient yeast dextrose broth and the commercial fermentation medium, were supplemented with 0.5 M NaCl and 0.1 mM glycine betaine according to Bonaterra et al. (2005, 2007). E325 was cultured at ARS-USDA laboratory and commercial facility, then freeze dried with cryoprotectants and applied to Gala apple blossoms in an orchard.
In 2009, initial population sizes on blossom stigmas, and areas under population-size curves (Aps), were greater for osmoadapted than non-osmoadapted E325. However, comparison of treatments based on areas under the daily-growth curves (Adg) indicated no differences.
Results were confirmed by a second trial in 2010. This led us to examine the stability of the E325 preparations prior to field application.
Preparations used for field tests continued to be maintained at -20°C and were sampled periodically to estimate viable concentrations.
Separate stability tests were also performed involving osmoadapted E325 with and without cryoprotectants.
Additionally, we evaluated survival and growth of osmoadapted E325 on both the stigmas and hypanthia of detached crab apple blossoms.
Osmoadaptation improved the survival of E325 during freeze drying and subsequent storage prior to application, but did not eliminate the need for cryoprotectants.
This production method, however, did not increase the survival of E325 on blossom stigmas under low relative humidity in the orchard (45% average) or laboratory (50 or 70%), but was shown in the laboratory to increase survival and growth in the blossom hypanthium.
Further orchard experimentation is necessary to verify this.
Publication
Authors
P.L. Pusey, C. Wend
Keywords
fire blight, biological control, Malus, apple, cryoprotectant
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