Effects Of2-Phenylethanol(PEA)on Citrus Blue Mold And Biocontrol Yeast34-9

Postharvest diseases of citrus fruits cause huge losses, biocontrol has been proved to be one of the most promising alternative methods to chemical fungicides in preventing postharvest diseases. Our previously study has revealed that the biocontrol strain34-9of Kloeckera apiculata secreted2-Phenylethanol （PEA） which had significant antifungal activity.In this paper, the effect and mechanism of PEA on citrus blue mold and biocontrol yeast34-9were studied. The main results were as followed;1. In vitro, It was0.2%of the minimum inhibitory concentration （MIC） of PEA against Penicillium italicum and0.8%of the minimum fungicidal concentration （MFC）. In vivo tests on citrus indicated that the PEA effectively controlled the infection of blue mold. Moreover, PEA had a wide range effects on other fungal diseases, including citrus green mold, citrus anthracnose, citrus sour rot, citrus black rot, apple blue mold, apple gray mold, mango anthracnose, mango stem-end rot, tomato early blight, tomato rhizopus rot, grape gray mold and grape rhizopus rot.2. Conidia germination, germ-tubes elongation and the hyphae growth of P. italicum were strongly inhibited by PEA, while it had no significant effect on mycelia morphology. The observation by Scanning Electron Microscope （SEM） illustrated that the conidia germination and hyphae growth of P. italicum were inhibited, and the pathogenicity became weak after the citrus treated with PEA. The results indicated that PEA had no notable effect on cell membrane permeability of P. italicum by relative conductivity and fluorescence staining, while the observation by Transmission Tlectron Microscope （TEM） displayed that the mitochondrial structure was apparently changed by PEA.3. Pseudohyphae/hyphae of strain34-9was further formed through adding exogenous PEA in the medium; The SEM showed that PEA could induce biofilms formation on the surface of the citrus fruit by treated with strain34-9and PEA. Real time RT-PCR results revealed that the transcript expression level of the flocculation （Flo） gene34-9₃691was significantly improved after treated with0.2%PEA, indicating PEA as QSMs regulating the Flo gene expression of34-9, and enabling the yeast cells to produce pseudohyphae and form biofilms.