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United States Department of Agriculture

Agricultural Research Service

Title: Iron Bioavailability to Pseudomonas Fluorescens Strain A506 on Pear and Apple Blossoms

item Temple, T.N. - OSU
item Stockwell, V.O. - OSU
item Johnson, K.B. - OSU
item Loper, Joyce

Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: April 1, 2003
Publication Date: June 1, 2003
Citation: Phytopathology 93:S82. Publication no. P-2203-0604-AMA

Technical Abstract: Pseudomonas fluorescens strain A506 produces an antibiotic toxic to Erwinia amylovora in defined culture media containing at least 0.1mM FeCl3. To estimate the relative abundance of iron on blossoms, we used an iron biosensor [iron-regulated promoter (pvd) fused to an ice nucleation reporter gene (inaZ)] in A506. In four experiments on pear and apple trees, A506 pvd-inaZ expressed high ice nucleation activity (INA) on blossoms indicating limited iron bioavailability. A506 pvd-inaZ expressed less INA on blossoms sprayed with an iron chelate (0.1mM FeEDDHA) than on blossoms sprayed with water, indicating that 0.1 mM FeEDDHA increased the levels of iron available to A506 pvd-inaZ in this habitat. Lower concentrations (0.01mM) of FeEDDHA did not significantly increase iron available to A506 on blossoms. These results indicate that apple and pear blossoms represent an iron-limited environment, which is likely to support antibiosis by A506, and adding at least 0.1mM FeEDDHA is required to significantly increase the level of bioavailable iron to A506 on blossoms.

Last Modified: 4/17/2015
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