Silver nanoparticles suppress the occurrence of anthracnose in Catalpa bungei: Efficacy evaluation and mechanistic analysis

Silver nanoparticles (AgNPs) are known for their broad-spectrum antimicrobial activity and offer distinct advantages as antimicrobial agents, including high efficacy and low tendency for resistance development. However, the mechanisms by which AgNPs inhibit plant fungal pathogens remain unclear, particularly in anthracnose caused by Colletotrichum gloeosporioides . Therefore, it is essential to elucidate the antifungal mechanisms of AgNPs against this pathogen. In this study, we demonstrated that AgNPs effectively inhibit mycelial growth and spore germination of C. gloeosporioides at concentrations of 5   mg   L −1 and 20   mg   L −1 . Mechanistic investigations revealed that AgNPs suppress the expression of genes related to reactive oxygen species (ROS) scavenging and cell wall integrity, rather than causing disruption of cell membrane integrity. Furthermore, AgNPs treatment significantly reduced anthracnose disease severity in Catalpa bungei leaves. Additional results indicated that AgNPs may enhance ROS burst in C. bungei by up-regulating the expression of RBOH genes, which in turn promote the expression of pathogenesis-related (PR) protein genes. Collectively, these findings clarify the potential mechanisms of AgNPs antifungal activity and provide a theoretical basis for their practical application in the management of anthracnose, as well as for resistance breeding in forestry timber species.