Australasian Plant Pathology (2000) 29, 164-169

D. Hüberli, I.C. Tommerup and G.E. St.J. Hardy (2000)
False-negative isolations or absence of lesions may cause mis-diagnosis of diseased plants infected with Phytophthora cinnamomi
Australasian Plant Pathology 29 (3), 164-169
Abstract: In a series of growth cabinet, glasshouse and field experiments, tissue samples from living clonal Eucalyptus marginata (jarrah) were incubated immediately after sampling on agar (NARPH) selective for Phytophthora. Phytophthora cinnamomi was recovered 3–6 months after inoculation from 50% of samples with lesions and 30% of symptomless samples. However, up to 11% of samples with and without lesions and from which P. cinnamomi was not initially isolated contained viable pathogen. This was shown by removing tissue which had not produced any growth of P. cinnamomi on NARPH plates, cutting it into smaller sections, washing in sterile deionised water repeatedly for 9 days, and replating. Plating stem or bark tissue directly onto NARPH produced false-negative results for nineP. cinnamomi isolates and six jarrah clones. The behaviour of the pathogen indicates that it could be present as dormant structures, such as chlamydospores, that need to be induced to germinate. Alternatively, fungistatic compounds in the tissue needed to be removed to allow the pathogen to grow. These results have important implications for disease diagnosis and management, disease-free certification and quarantine clearance.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Daniel Hüberli

Research topic(s) for pests/diseases/weeds:
identification/taxonomy
quarantine treatments/regulations/aspects

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Phytophthora cinnamomi	Eucalypt (Eucalyptus)