The production of the isoflavonoid phytoalexins medicarpin, sativan and vestitol by lucerne (<i>Medicago sativa</i> L) in response to substances, named elicitors, released into culture fluids of the plant-pathogenic fungus <i>Verticillium albo-atrum</i> was investigated. Methods for establishing the production of phytoalexins were studied and developed to use for screening substances from culture filtrates for elicitor activity. A method of reverse-phase High Performance Liquid Chromatography was developed in order to obtain quantitative measurements of elicitor activity. The presence of elicitors in extracts of the mycelium of the fungus was also investigated. Attempts were made to isolate and purify the component(s) from culture filtrates and mycelial extracts of <i>Verticillium</i> responsible for elicitor activity. Activity was not removed from culture filtrates by dialysis. Studies were made initially using Sephadex G-200 gel chromatography and anion exchange chromatography. Subsequently, the culture filtrate elicitor was found not to be precipitated in 80% v/v ethanol while inactive components were. Biogel P-10 chromatography produced an apparently homogeneous fraction on which preliminary chemical studies were performed. A molecular weight of 3000-4000 was indicated for the material. This fraction proved capable of further resolution. Cation and anion exchange chromatography was used for this purpose. The most active fraction obtained was retained by the anion exchanger but not a cation exchanger. This could be resolved by analytical scale reverse-phase liquid chromatography into multiple components. Colorimetric assays showed the material to be predominately peptide although a small amount of carbohydrate was present. The most active material from mycelial extract was not retained by either cation or anion exchangers. Colorimetric assays showed it to be predominately carbohydrate although protein was also detectable.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:636915 |
| Date | January 1987 |
| Creators | Evans, D. J. |
| Publisher | Swansea University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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