Postharvest Biocontrol of Blue Mold in Shatangju Mandarins by the Antagonistic Yeast Meyerozyma guilliermondii SR1

Blue mold caused by Penicillium italicum triggers severe tissue decay and limits postharvest shelf life, representing the primary constraint to the commercial supply chain of Shatangju mandarins (Citrus reticulata cv. Shatangju). In this study, the biocontrol efficacy of an antagonistic yeast, Meyerozyma guilliermondii SR1, against postharvest blue mold in Shatangju mandarins was evaluated. The results showed that SR1 significantly inhibited the in vitro growth of P. italicum, delayed disease progression and restricted pathogen sporulation in inoculated fruits during storage. Furthermore, SR1 rapidly colonized fruit wounds to establish a population advantage and enhanced the antioxidant defense capacity of the host fruits. Meanwhile, SR1 treatment significantly reduced postharvest weight loss, with no significant differences in total soluble solids (TSS) and titratable acidity (TA) compared with the control. In conclusion, M. guilliermondii SR1 showed significant biocontrol efficacy against postharvest blue mold in Shatangju mandarins, which provides an experimental basis for the research and development of green citrus postharvest preservatives.