An interdisciplinary approach was utilized to study the toxicity of aluminum (Al) to soilborne plant pathogens with the goal of developing a pathogen-suppressive potting medium containing non-phytotoxic, Al-organic matter complexes. Toxicological studies addressed the toxicity of monomeric Al species to <i>Thielaviopsis basicola</i> and <i>Phytophthora parasitica</i> and documented the sensitivity of these organisms to the metal. Until recently, research on Al-toxicity to fungi has only focused on the trivalent Al cation (Al<sup>3+</sup>) which is also considered the most phytotoxic Al ion. The toxicity of Al-hydrolysis species to fungi were tested by modeling in vitro test solution equilibria using GEOCHEM-PC and correlating the predicted values of Al-species activities with reduction in spore production of the two pathogens. Chlamydospore production of <i>T. basicola</i> was negatively correlated with Al<sup>3+</sup> activity, whereas inhibition of sporangia production of <i>P. parasitica</i> was related to the activity of multiple monomeric Al species. Toxicity of Al to <i>T. basicola</i> was observed in solutions containing ≥ 20 micromolar Al. Sensitivity of <i>P. parasitica</i> to Al was observed at < 1.0 micromolar Al, suggesting that <i>P. parasitica</i> is more sensitive to Al than <i>T. basicola</i>. Using fluorescence microscopy, the localized accumulation of Al in pathogen tissues was detected using lumogallion, an Al-specific, fluorescent stain. Accumulation of Al was observed under various chemical conditions, ranging from salt solutions to more complex systems containing Al-peat complexes. An ecological approach was applied to study the dynamic interactions of soil chemical and physical properties with soil microflora for the suppression of <i>P. parasitica</i> in a medium amended with Al<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub> and composted swine waste (CSW). Abiotic and biological mechanisms of pathogen suppression were incorporated into the CSW-amended medium. Al-mediated suppression resulted in reduction of sporangia production in medium exhibiting K-exchangeable Al levels > 2 micromolar Al. Biological suppression also resulted in reduction of sporangia production and this suppression was maintained after Al levels dropped below the threshold necessary for abiotic suppression. The incorporation of abiotic and biological control mechanisms into a potting media may facilitate suppression of a wide range of soilborne pathogens and enhance applicability of disease-suppressive media in a disease management strategy.
| Identifer | oai:union.ndltd.org:NCSU/oai:NCSU:etd-10222003-020101 |
| Date | 22 October 2003 |
| Creators | Fichtner, Elizabeth Jeanne |
| Contributors | T. Jot Smyth, H. David Shew, Dean L. Hesterberg, D. Mike Benson |
| Publisher | NCSU |
| Source Sets | North Carolina State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://www.lib.ncsu.edu/theses/available/etd-10222003-020101/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to NC State University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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