Mode of action of Talaromyces sp. KNB422, a biocontrol agent against rice seedling diseases

Talaromyces sp. KNB422, isolated from a rice seedling, is a fungus that is highly effective against several rice seedling diseases. To clarify its mode of action, the interaction between KNB422 and Rhizopus oryzae, Pythium graminicola, and Gibberella fujikuroi was examined in vitro. In a PDA medium, KNB422 expanded its hyphae over the mycelia of the pathogens. The interaction between KNB422 and R. oryzae and P. graminicola was examined by scanning electron microscopy. The hyphae of KNB422 grew around and then penetrated the hyphae of the pathogens. Furthermore fluorescence microscopy revealed that KNB422 grew toward, penetrated into and dissolved the G. fujikuroi hyphae. KNB422 has the ability to parasitize pathogens, such as R. oryzae, P. graminicola, and G. fujikuroi, to prevent their growth.