Generation of a Green Fluorescent Protein-Expressing Strain in <i>Diaporthe destruens</i> Useful for Observing Infection Processes in Sweet Potato Tissues

Foot rot of sweet potato caused by <i>Diaporthe destruens</i> has recently caused severe agricultural damage in Japan. Understanding the processes of infection of <i>D. destruens</i> will allow for the design of effective management measures against this disease. The transformation of green fluorescent proteins (GFPs) into phytopathogenic fungi allows us to clarify the infectious behavior of pathogens through optical observations. In this study, we introduced the GFP gene into <i>D. destruens</i> using the restriction enzyme-mediated integration (REMI) method to establish a strain suitable for observing infection processes. The established strain, F3GFP-3, exhibited growth characteristics and pathogenicity similar to those of the original strain. Whole-genome sequencing of F3GFP-3 revealed three insertions of the GFP vector into its genome, all of which were located in one of the de novo assembled contigs. In the inoculation experiment, F3GFP-3 germinated at a high rate and extended longer hyphae when the plant surface was wounded. Inside the plant, F3GFP-3 localized to the intercellular space in the stems and tubers. Our study showed the successful transformation of <i>D. destruens</i> using the REMI method as a means to observe pathogenic processes of infection.