Xylem sap proteome studies on susceptible or resistant tomato (Solanum lycopersicum) inoculated with endophytic and/or pathogenic strains of Fusarium oxysporum f.sp. lycopersici were conducted to get insights into the molecular differences between endophyte- and R-gene-mediated resistance (EMR and RMR). The EMR and RMR proteomes were compared to each other and to the mock control. Interestingly, specific PR-5 isoforms were found to exclusively accumulate during endophyte or genetic resistance, providing excellent markers to distinguish both resistance types at the molecular level.