Submitted to: Acta Horticulturae
Publication Type: Abstract Only
Publication Acceptance Date: 1/31/2011
Publication Date: 5/1/2011
Citation: Pusey, P.L., Wend, C. 2011. Survival of Pantoea agglomerans E325 as fire blight biocontrol agent when osmoadapted in high-saline medium. Acta Horticulturae. 896:467-470. Interpretive Summary:
Technical Abstract: Pantoea agglomerans strain E325 is available commercially as the active ingredient in a freeze-dried product (Bloomtime FDTM) of Northwest Agricultural Products (NAP) for biological control of fire blight. Osmoadaptation, which involves the combination of Pantoea agglomerans strain E325 is available commercially as the active ingredient in a freeze-dried product (Bloomtime FDTM) of Northwest Agricultural Products (NAP) for biological control of fire blight. Osmoadaptation, which involves the combination of saline osmotic stress and osmolyte amendment to growth media, was previously reported for the postharvest biocontrol agent P. agglomerans strain EPS125 (Bonaterra et al., 2005). We evaluated this process as a means to improve the survival of E325 during freeze drying, subsequent storage, and establishment on pomaceous blossoms under dry orchard conditions. Media used in the study were both defined (glucose minimal medium; GMM) and complex (nutrient yeast dextrose broth and NAP production medium). Growth of E325 in media amended with 0.4 or 0.5 M NaCl followed by freeze drying resulted in a 10- to 100-fold greater cell survival compared to non-amended media. (Cells from both the amended and non-amended media were combined with cryoprotectants prior to freeze drying.) Although amendment with the osmolyte glycine betaine at levels of 0.1 to 0.5 mM was important for E325 growth in NaCl-amended GMM, it did not affect bacterial growth in the NaCl-amended complex media, possibly because yeast or beef extracts in these media already contain GB. The NaCl amendment in complex media also significantly improved the stability of freeze dried E325 preparations stored at -20°C, as indicated by a 100- to 1000-fold increase in cell survival from a sampling time soon after freeze drying to 6 months later. The effect of “inert” ingredients in the commercial product on E325 survival was not considered. Work is still in progress to determine whether osmoadaptation enhances E325 establishment on flower tissues. At present, we conclude that this procedure enhances the survival of E325 during and after cells are freeze dried for use in commercial preparations for fire blight management.