Visualization of the Infection and Colonization Process of Dendrobium officinale Using a Green Fluorescent Protein-Tagged Isolate of Fusarium oxysporum

soft rot is a widespread and destructive disease caused by that can seriously affect yield and quality. To better understand the fungal infection and colonization, we successfully created an labeled with green fluorescent protein using the -mediated transformation method. Transformants had varying fluorescence intensities, but their pathogenicity did not differ from that of the wild type. Fluorescence microscopy revealed that primarily entered the aboveground portion of through the leaf margin, stomata, or by direct penetration of the leaf surface. It then colonized the mesophyll and spread along its vascular bundles. exhibited typical symptoms of decay and wilting at 14 days postinoculation, accompanied by a pronounced fluorescence signal in the affected area. The initial colonization of in the subterranean region primarily involved attachment to the root hair and epidermis, which progressed to the medullary vascular bundle. At 14 days postinoculation, the root vascular bundles of exhibited significant colonization by . Macroconidia were also observed in black rot tissue. In particular, the entire root was surrounded by a significant number of chlamydospore-producing mycelia at 28 days postinoculation. This approach allowed for the visualization of the complete infection process of and provided a theoretical foundation for the development of field control strategies.