Efficient control of the fungal pathogens Colletotrichum gloeosporioides and Penicillium digitatum infecting citrus fruits by native soilborne Bacillus velezensis strains.

Destruction of citrus fruits by fungal pathogens during preharvest and postharvest stages can result in severe losses for the citrus industry. Antagonistic microorganisms used as biological agents to control citrus pathogens are considered alternatives to synthetic fungicides. In this study, we aimed to identify fungal pathogens causing dominant diseases on citrus fruits in a specialized citrus cultivation region of Vietnam and inspect soilborne isolates with antifungal activity against these pathogens. Two fungal pathogens were characterized as and based on morphological characteristics and ribosomal DNA internal transcribed spacer sequence analyses. Reinfection assays of orange fruits confirmed that causes stem-end rot, and triggers green mold disease. By the heterologous expression of the green fluorescent protein (GFP) in using -mediated transformation, we could observe the fungal infection process of the citrus fruit stem-end rot caused by for the first time. Furthermore, we isolated and selected two soilborne strains with strong antagonistic activity for preventing the decay of citrus fruits by these pathogens. Molecular analyses of 16 S rRNA and genes showed that both isolates belong to . Antifungal activity assays indicated that bacterial culture suspensions could strongly inhibit and , and shield orange fruits from the invasion of the pathogens. Our work provides a highly effective -based preservative solution for combating the fungal pathogens and to protect citrus fruits at the postharvest stages.