Isolation and Identification of Postharvest Rot Pathogens in Tangelo and their Potential Inhibition with Acidic Electrolyzed Water

Abstract

This study focused on the identification of rot-causing fungi in tangelo, with a particular emphasis on investigating the inhibitory effects of acidic electrolyzed water on the identified pathogens. The dominant strains responsible for postharvest decay were isolated from infected tangelo fruits and characterized through morphological observation, molecular identification, and pathogenicity detection. Two strains were isolated from postharvest diseased tangelo fruits, cultured and morphologically characterized, and had their gene fragments amplified using primers ITS1 and ITS4. The results revealed the rDNA-ITS sequence of TF1 and TF2 were 100% homologous with those of Penicillium citrinum and Aspergillus sydowii. These isolated fungi were confirmed to induce tangelo disease, and subsequent re-isolation validated their consistency with the inoculum. Antifungal tests demonstrated that acidic electrolyzed water exhibited a potent inhibitory effect on Penicillium citrinum and Aspergillus sydowii, with EC50 values of 85.4 µg/mL and 60.12 µg/mL, respectively. The inhibition zones of 150 µg/mL acidic electrolyzed water to 2 kinds of pathogenic fungi were over 75 mm in diameter. Furthermore, treatment with acidic electrolyzed water resulted in morphological changes such as bending and shrinking of the fungal hyphae surface. In addition, extracellular pH, conductivity, and absorbance at 260 nm of the fungi hypha significantly increased post-treatment with acidic electrolyzed water. Pathogenic morphology and IST sequencing analysis confirmed Penicillium citrinum and Aspergillus sydowii as the primary pathogenic fungi, with their growth effectively inhibited by acidic electrolytic water.