The role epicuticular waxes play in resistance of brassicas to foliar diseases was investigated for two known brassica pathogens, <i>Alternaria brassicicola</i> and <i>Erysiphe cruciferarum</i>, a weak parasite <i>Alternaria alternata</i> and a non-pathogen <i>Erysiphe graminis</i>. Waxes of swede, oilseed rape and Brussels sprout leaves from different leaf positions were found to be composed of eight analogous compounds but in varying proportions. Epicuticular waxes from seven Brussels sprout mutant lines, in comparison to a commercial variety, again had eight similar groups of compounds, however the variations in proportions were more distinct. Correlations could be made betweeen prevalence of certain compound groups and wax crystal configuration. Waxes containing high ketones and hydrocarbons had crystals in the form of rods which projected from the cuticle and these surfaces tended to be waxy. Temperature was seen to transform the crystalline configuration of wax crystals, whereas light intensity altered their dimensions. Waxy surfaces had the lowest wettability and permeability, and also tended to be most resistant to <i>Alternaria</i> infection. Infection by <i>Erysiphe cruciferarum</i> seemed to be related to the genetic background of the host and not surface phenotype. Treatment of the surface with surfactant, which reduced the wettability, and environmental conditions which increased wettability had equivalent effects on <i>Alternaria</i> infection but variations in <i>Erysiphe</i> infections could not be explained by changes in leaf surface wettability.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:641564 |
| Date | January 1992 |
| Creators | Berry, Lorraine Anne |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/26320 |
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