Populations of pathogenic and non-pathogenic bacteria were studied in Phaseolus vulgaris. Virulent isolates of the homologous pathogen Pseudomonas phaseolicola multiplied at rates and to final populations which suggested that no inhibitory reaction with the plant was involved. Necrosis-inducing heterologous pathogens multiplied at lower rates and to lower final populations than the homologue. Non-pathogens were static in tissue. A suggestion made elsewhere that the behaviour of non-pathogens and pathogens was determined by their different oxidase activities was not supported. The growth of non-pathogenic bacteria co-inoculated into bean leaves with the homologous or heterologous pathogens was stimulated, indicating that the plant intercellular environment was modified by pathogens to favour general bacterial growth. Inoculation of non-pathogens with nutrient amendments did not affect their behaviour in plant tissue, but when leaves were held in water-soaked conditions following inoculation, non-pathogens multiplied and the heterologous pathogens were stimulated to the same rate and almost to the same final population of the homologue. Free water appears to be the initial limiting factor for the multiplication of bacteria in the intercellular spaces. The growth of heterologous pathogens co-inoculated with the homologue was also stimulated. Pathogenic specificity may be explained by the action of bacterial toxins acting directly or indirectly to increase host cell membrane permeability. When beans were challenged with high concentrations of inocula of non-pathogens, a general inhibition occurred against pathogenic bacteria which were subsequently inoculated. Inhibition induced in plants by bacteria may regulate their final populations.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:593868 |
| Date | January 1972 |
| Creators | Young, J. M. |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU388116 |
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