An investigation into pre-penetration behaviour of the beta strain of C. lindemuthianum revealed that normal germination processes leading to appressorium formation were largely nutrient independent. However, the French bean phylloplane environment favoured rapid pre-penetration development irrespective of whether the leaves were susceptible or not. Culture filtrates of the pathogen elicited a hypersensitive response from both susceptible and resistant cultivars and caused a discolouration of wounded veinal tissues. Added nutrient substances often caused a delay in conidial germination and in certain cases led to suppression of appressorium formation. Synthetic chelating agents had no stimulatory effect on the pathogen except to modify the adverse influence certain cations had on appressorium formation. Sodium undecylenate had a strong inhibitory influence on conidial germination but did not affect further development following appressorium formation. Certain yeast isolates reduced the antifungal effects of the fatty acid salt. Pink yeasts in the presence of castor bean seed oil inhibited appressorium development indicating the possibility of manipulating the chemical environment of the phylloplane to promote antagonistic interactions. Isolates of epiphytic microorganisms including a non-fluorescent pseudomonad, Aureobasidium pullulans and Trichoderma species exhibited a significant inhibitory influence on the conidial germination of the pathogen. However, lesion development was not influenced by the activities of the antagonists as host penetration from appressoria on the few germinating conidia was unaffected. Physiologic specialization of the anthracnose pathogen was indicated by the observed resistant response to infection by the beta strain of some individual plants of the susceptible test cultivar, the Prince, which may have had a genetic basis. Possible reasons for the observed behaviour of the pathogen under different experimental conditions and the significance in terms of disease control are discussed.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:447623 |
| Date | January 1982 |
| Creators | Aloysius, G. R. |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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