Broad-spectrum inhibition ofPhytophthora infestansby root endophytes

Summary Phytophthora infestans ( Phy. infestans ) is a devastating pathogen of tomato and potato. It readily overcomes resistance genes and applied agrochemicals. Fungal endophytes provide a largely unexplored avenue of control against Phy. infestans . Not only do endophytes produce a wide array of bioactive metabolites, they may also directly compete with and defeat pathogens in planta . Twelve isolates of fungal endophytes from different plant species were tested in vitro for their production of metabolites with anti- Phy. infestans activity. Four well-performing isolates were evaluated for their ability to suppress nine isolates of Phy. infestans on agar medium and in planta. Two endophytes reliably inhibited all Phy. infestans isolates on agar medium, of which Phoma eupatorii isolate 8082 was the most promising. It nearly abolished infection by Phy. infestans in planta . Here we present a biocontrol agent, which can inhibit a broad-spectrum of Phy. infestans isolates. Such broadly acting inhibition is ideal, because it allows for effective control of genetically diverse pathogen isolates and may slow the adaptation of Phy. infestans.