Antifungal Effects of Peracetic Acid on Fungi Causing Black Stain in Asian Pear

Black stain is a postharvest disease that occurs on the skin of Niitaka pears (Pyrus pyrifolia Nakai)during cold storage, causing significant economic losses to pear production. We investigated theantifungal effects of peracetic acid (PAA), which is a strong oxidizing agent and an effectivedisinfectant, on fungi that cause black stain, and we confirmed its preventive effect on black stainafter application to pears. Fungal isolates were identified as the type species of Cladosporiumporophorum through molecular identification of internal transcribed spacer regions and the largesubunit of nuclear ribosomal RNA gene. To assess antifungal effects of PAA and NaOCl on C. porophorum, several susceptibility tests including disc diffusion, mycelial growth tests, andmicrodilution assays were performed. A comparison of antifungal effects of PAA and NaOCl on C. porophorum showed that the PAA concentrations that inhibit mycelial growth or metabolic activitywere two-fold lower than those of NaOCl. When conidia were used as a fungal inoculum, PAAcompletely inhibited fungal growth and metabolic activity at concentrations of 0.02%–0.08% and0.005%, respectively, whereas PAA concentrations of at least 0.1% were required to achievesufficient growth inhibition of growing mycelium. After application of PAA to pears, the incidencerate of black stain in fruits treated with 0.1% PAA was approximately half (31.1% ± 1.9%) of thatin untreated fruits (58.8% ± 4.5%). Therefore, the antifungal effects of PAA on fungi causing blackstain may help reduce postharvest losses of Niitaka pears during cold storage. KCI Citation Count: 0