Fusarium citri as an entomopathogenic fungus mediating plant resistance against insect pests and phytopathogens

Fusarium citri has been historically recognized as a phytopathogen but never as an entomophagous fungus (EPF) with plant endogeneity. In the present study, an F. citri strain, FcS1GZL-1, was isolated and identified from diseased Spodoptera litura larvae in a soybean field. The pathogenicity and antagonistic activity of FcS1GZL-1 against five insect pests were assessed, as well as its ability to colonize plants via root irrigation, and its induced resistance to insect pests and phytopathogens was also measured. The expression of plant resistance related genes was analyzed using real-time RT-PCR. According to the results, the FcS1GZL-1 strain could not only kill insect pests with high pathogenicity but also inhibited phytopathogen growth in vitro. Furthermore, the FcS1GZL-1 strain could repel insect pest feeding and enhance plant resistance to phytopathogens through endophytic customization following root irrigation, which upregulated 12 genes related to the jasmonic acid, salicylic acid, ethylene, and pathogen-related defense pathways in soybean roots. Herein, we present the first documented case of F. citri naturally infecting insects, and its dual role in controlling insect pests and phytopathogens, with promising biocontrol applications.