Iron Competition as an Important Mechanism of Pulcherrimin-Producing sp. Strains for Controlling Postharvest Fungal Decays on Citrus Fruit.

This study identified and tested fruit-isolated yeasts against three major postharvest citrus pathogens, namely, , , and , and further evaluated the impact of FeCl on the biocontrol efficiency of pulcherrimin-producing strains. Based on the characterization of the pigmented halo surrounding the colonies and the analysis of the D1/D2 domain of 26S rDNA, a total of 46 sp. were screened and identified. All 46 strains significantly inhibited the hyphal growth of , , and , and effectively controlled the development of green mold, blue mold and sour rot of citrus fruit. The introduction of exogenous FeCl at certain concentrations did not significantly impact the pulcherriminic acid (PA) production of pigmented strains, but notably diminished the size of pigmented zones and the biocontrol efficacy against the three pathogens. Iron deficiency sensitivity experiments revealed that and exhibited higher sensitivity compared to , indicating that iron dependence varied among the three pathogens. These results suggested that strains, capable of producing high yields of PA, possessed great potential for use as biocontrol agents against postharvest citrus diseases. The biocontrol efficacy of these yeasts is mainly attributed to their ability to competitively deplete iron ions in a shared environment, with the magnitude of their pigmented halo directly correlating to their antagonistic capability. It is worth noting that the level of sensitivity of pathogens to iron deficiency might also affect the biocontrol effect of pulcherrimin-producing .