Infection process of Corynespora cassiicola tagged with GFP on Hevea brasiliensis

Corynespora leaf fall (CLF) disease, caused by the fungal pathogen Corynespora cassiicola, is a major disease of rubber tree (Hevea brasiliensis) that affects the production of natural rubber. To study its pathogenesis, we developed a C. cassiicola transformant tagged with green fluorescent protein and studied it using fluorescence and confocal laser scanning microscopy. The transformed isolate retained its pathogenicity and grew similarly to the wild-type. Conidia germinated and produced germ tubes 4 h after inoculation, after which the fungus infected leaves through wounds; extended into veins, cells, and intercellular spaces within 24 h; produced abundant mycelia on the surfaces of diseased leaves within 48 h; and began to form conidiophores and conidia within 72 h. The infection process of C. cassiicola on H. brasiliensis was complete within 72 h. Our findings may be useful for predicting the path of CLF disease and evaluating H. brasiliensis resistance to C. cassiicola via leaf colonization studies.