<I>Phytophthora cinnamomi </I>var. <I>cinnamomi, Pythium ultimum </I>var. <I>ultimum </I>and <I>Pythium undulatum </I>were successfully isolated from naturally regenerating <I>Pinus sylvestris </I>forests across north Scotland. Molecular and morphological characterisation enabled accurate identification of these Oomycetes to the variety level. <I>In vitro</I> and glasshouse pathogenicity trials demonstrated that under artificial temperature, light and water regimes the Oomycetes had the potential to reduce plant growth and cause chlorosis of the <I>P. sylvestris</I> foliage after two months. Soil pH was also determined as having a significant effect on <I>P. sylvestris </I>growth in terms of foliage colour and dry mass. Biological control <I>in vitro </I>experiments with <I>Bacillus subtilis</I> and <I>Pseudomonas fluorescens</I> produced significant inhibition of Oomycete growth but on transfer to the glasshouse trials, antagonism was not observed. This study was undertaken to establish the presence of fine root pathogens, namely those belonging to the Oomycetes, within regenerating <I>Pinus sylvestris</I> forests in northern Scotland. The identify of the pathogens was determined using morphological and molecular biology techniques. The virulence of the fine root pathogens on <I>Pinus sylvestris </I>seedlings (1 + 0) was then determined by a series of <I>in vitro</I> and glasshouse trials. Interactions between soil pH and bacterial biological control agents were also tested against each of the pathogens. Pathogen trials were undertaken to show the potential effect of the Oomycetes on <I>Pinus sylvestris </I>seedlings. The glass house trial was scored on foliage colour and dry weight of seedlings 18 months of age, grown in pH amended Irish moss peat. In comparison to the control, inoculation with <I>P. cinnamomi</I> caused a significantly greater frequency of chlorotic/dead seedlings. In contrast, inoculation with <I>P. undulatum </I>(syn. <I>P. dimorphum</I>) resulted in a greater number of healthy seedlings than the control. No significant difference in the proportion of healthy and chlorotic/dead seedlings was found between the bio-control bacteria groups. pH was found to have a significant effect on seedling growth. At pH 7, compared to pH 3, there was a significant greater likelihood of the seedlings being chlorotic/dead.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:311160 |
| Date | January 2000 |
| Creators | Bodles, William J. A. |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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