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Title: Mycotoxin production and DNA polymorphism of Alternaria species isolated from oilseed rape
Author: Forbes-Smith, Michael Ronald
Awarding Body: University of London
Current Institution: University College London (University of London)
Date of Award: 1994
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Samples of rapeseed and meal were collected and examined microbiologically in order to determine the occurrence of mycotoxigenic moulds colonising oilseed rape in Great Britain. Up to 19 fungal genera were detected on samples at harvest and during storage; the predominant mould in seed was Alternaria alternata. Moulds identified on meal included Penicillium and A. alternata. When isolates of Alternaria spp were grown on rice, rapeseed and meal, five metabolites were detected — altenuene (ALT), altertoxin-I (ATX-I), alternariol (AOH), tenuazonic acid (TeA) and alternariol methyl ether (AME). These compounds were identified by their UV spectra and thin layer chromatography with standards. In order to quantify these compounds by high performance liquid chromatography, solvent optimisation techniques were adopted. Optimum separation on an octyl column occurred with an isocratic mobile phase consisting of 41.7% aqueous zinc sulphate solution (300mg/L), 30.3% methanol, 18.1% acetonitrile and 9.9% tetrahydrofuran. Production of mycotoxins was greater on rice than on rapeseed or meal. The most abundant metabolite produced on all substrates was TeA. Bioassay studies, including those with brine shrimp and cells isolated from rapeseed leaves, were employed to investigate the toxicity oi Alternaria mycotoxins; TeA was the most toxic of the five metabolites. Production of TeA by A. alternata was quantified on rapeseed and meal under a series of temperature and moisture conditions ranging between 10–30°C and 6.0–55.0% respectively. Higher temperature and moisture levels favoured TeA accumulation but under commercial storage conditions (i.e. ≤ 9% moisture), none was produced. A nitrogen-containing compound which was toxic to fungal spores was produced on rice by an isolate of A. alternata. that did not produce the typical Alternaria toxins. The compound was purified using solid phase and preparative TLC. Analysis of polymerase chain reaction products from genomic DNA of Alternaria spp. showed polymorphisms between morphological features and between toxigenic and non-toxigenic isolates of Alternaria spp.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available