PCR test to distinguish between Guignardia citricarpa and G. mangiferae
As reported earlier in EPPO RS 2002/082, strains which were previously considered as ‘non-pathogenic strains of Guignardia citricarpa sensu lato’ belong to another species Guignardia mangiferae. A PCR method using specific primers was developed in New Zealand to distinguish between the citrus black spot pathogen Guignardia citricarpa (EU Annexes) and the harmless Guignardia mangiferae. No cross reaction was obtained with Colletotrichum gloeosporioides which is the most common contaminant found in black spot lesions. This PCR method was further improved by a direct DNA extraction from fruit lesions, thus eliminating the need to culture the fungus. With this improvement, results of the PCR test could be obtained within one day to verify the presence or absence of G. citricarpa in fruit consignments.
Sources
Meyer L, Sanders GM, Jacobs R, Korsten L (2006) A one-day sensitive method to detect and distinguish between the citrus black spot pathogen Guignardia citricarpa and the endophyte Guignardia mangiferae. Plant Disease 90(1), 97-101.