Submitted to: Phytopathology
Publication Type: Proceedings
Publication Acceptance Date: 4/1/2004
Publication Date: 6/1/2004
Citation: Pusey, P.L. 2004. Biochemical analyses of pomaceous stigma exudates and relevance to biological control of fire blight. Phytopathology. 94:S86.
Technical Abstract: Microbial antagonism toward Erwinia amylovora on stigmas of pear and apple flowers has been widely demonstrated. Knowing the chemistry of stigma exudates could advance the selection and use of antagonists. Stigmas of different pomaceous cultivars and ages were analyzed for sugars and amino acids. Flowers collected in groups of 50 were pooled for analysis. Anthers were removed and stigma tips submerged and sonicated in 600 ul water. Pollen and macromolecules were removed by centrifugation and filtration. Sugars were converted to trimethylsilyl derivatives and analyzed by GC. Amino acids were converted to fluorescent derivatives using o-phthaldialdehyde and separated by HPLC. Predominant sugars were glucose and fructose. Predominant amino acids were asparagine, glutamine, proline and serine. Sold and liquid media developed with these compounds were used to evaluate antagonists based on competitive and antibiotic inhibition of E. amylovora. Preliminary results were consistent with in vivo flower assays. Stigma-based media are now being modified to understand modes of antagonism and their relation to chemical constituents on stigmas.