Species‐specific real‐time PCR for diagnosis of Phyllosticta citricarpa on Citrus species

Phyllosticta citricarpa (teleomorph Guignardia citricarpa ) is the causal agent of citrus black spot, a disease causing lesions on fruits and leaves of different Citrus species in Asia, Australia, South Africa and South America. It is a quarantine organism in the European Union and the USA and hence a reliable differentiation between this species and other Phyllosticta species found on Citrus is essential. A differentiation based on morphology is often problematic, hence a range of molecular tests have been developed to distinguish P. citricarpa from other species present on citrus fruits, especially the endophyte Phyllosticta capitalensis (teleomorph Guignardia mangiferae ). However, these tests cannot distinguish P. citricarpa from the closely related Phyllosticta citriasiana , the causal agent of tan spot disease. In this study, a real‐time PCR was designed which is specific for P. citricarpa and does not amplify P. citriasiana or P. capitalensis DNA .