Amphotericin B and 5-flucytosine as fungicides against Penicillium italicum for citrus fruit rot

The expansion of the global population and improved living standards has created an increasing demand for fresh fruit. The combination of agricultural and medical development for new fungicides is one of the most effective approaches for keeping fruit fresh. Both amphotericin B and 5-flucytosine are quite safe and have a wide spectrum of antifungal activity. For the purpose of investigating their potential applications for preserving fruit freshness, we evaluated their antifungal efficiencies against Penicillium italicum in vitro and in vivo. The results showed that amphotericin B and 5-flucytosine significantly inhibited spore germination and the mycelial growth of P. italicum. The 5-flucytosine showed much better bioactivity than the well-known agricultural fungicide prochloraz, both in vitro and in vivo. Furthermore, crystal violet staining, propidium iodide dyeing, ultrastructural observation and the ergosterol content indicated that amphotericin B and 5-flucytosine destroyed the cellular ultrastructure and membrane integrity. In addition, nucleic acids (OD260) and proteins (OD280) escaped from P. italicum cells in a dose-dependent manner. The results of this study indicated that amphotericin B and 5-flucytosine have good potential as antifungal preservatives for postharvest citrus fruit due to their excellent antifungal effects, and that the primary mode of action was the destruction of the membrane integrity and permeability of P. italicum.