LAUSR

Abstract Green mold and blue mold caused by Penicillium digitatum and P. italicum respectively, are two main fungal diseases in Citrus reticulata (mandarin oranges) worldwide. They are difficult to prevent for the lack of effective antagonists. This study investigated the efficacy of Yarrowia lipolytica against these diseases in mandarins and the relative defense mechanisms. The results indicated that Y. lipolytica has a great potential to inhibit the infections by P. digitatum and P. italicum in mandarins, while both the decay incidence and lesion diameter decreased in Y. lipolytica treated mandarins, in a dose-dependent manner. Furthermore, Y. lipolytica treatment had no side effects on quality paraments of mandarins. In vitro tests demonstrated that, spore germination and germ tube length of P. digitatum and P. italicum were both inhibited by Y. lipolytica. In addition, Y. lipolytica had a better ability to adapt to the environment, occupy space and utilize nutrients than pathogens, which provided a favorable condition for Y. lipolytica to colonize wounds and surfaces of mandarins. This research also showed that, Y. lipolytica induced higher activities of polyphenol oxidase (PPO), peroxidase (POD), catalase (CAT), phenylalanine ammonia lyase (PAL), and increased the contents of flavonoid compounds and total phenols, which activated the defense mechanisms of mandarins. These results suggested that Y. lipolytica is a promising antagonistic yeast to control green mold and blue mold in mandarins.