G. citricarpa is a fungal pathogen which causes citrus black spot disease affecting a number of economically important citrus crops including oranges, mandarins, lemons and grapefruits. Though of tropical origin, the fungus has established itself and causes serious damage in subtropical climates, e.g. China, New South Wales (Australia) and South Africa. G. citricarpa has recently been added to the A1 quarantine list of EPPO and is suspected to cause significant losses if it were to be introduced and establish within the Mediterranean citrus-growing area. Importation of citrus planting material from countries where true G. citricarpa occurs is prohibited as the fungus can readily be carried on imported citrus fruits and due in part to the prohibition of several other non-European citrus pests. The risk of spread from such a pathway is relatively low. Diagnosis is made by laboratory visual assessment of black spot lesions and the identification of characteristic fungal structures (pycnidia) where symptoms are often variable and ambiguous.
Rapid testing using a Genie II instrument and the G. citricarpa LAMP kit is possible within 30 minutes allowing for decisive determinations to be made on consignments very rapidly. The assay can be used in parallel with the plant control assay (COX (- cytochrome oxidase gene) assay, which allows for the detection of host plant DNA, which acts as an internal control assay to assist in the interpretation of negative results.
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