Electrostatic Atomized Water Particles Induce Disease Resistance in Muskmelon (Cucumis melo L.) against Postharvest Fruit Rot Caused by Fusarium incarnatum

The postharvest quality of muskmelon can be affected by fruit rot caused by the fungus Fusarium incarnatum, resulting in loss of quality. The utilization of electrostatic atomized water particles (EAWPs) in agriculture applications has been shown to induce disease resistance in plants. Therefore, in this study, we determined the effect of electrostatic atomized water particles (EAWPs) on the disease resistance of muskmelon fruits against postharvest fruit rot caused by F. incarnatum. EAWPs were applied to muskmelon fruits for 0, 30, 60, and 90 min. EAWP-treated muskmelon fruits were inoculated with F. incarnatum, and disease progress was measured. Quantitative reverse-transcription polymerase chain reaction (qRT-PCR) of the chitinase (CmCHI) and β-1,3-glucanase (CmGLU) genes of Cucumis melo (muskmelon) was performed for EAWP-treated and -untreated muskmelon fruits. The activities of cell-wall-degrading enzymes (CWDEs), chitinase, and β-1,3-glucanase were also assayed in EAWP-treated and -untreated muskmelon fruits. The results showed that disease progress was limited by EAWP treatment for 30 min prior to pathogen inoculation. Muskmelon fruits treated with EAWPs for 30 min showed an upregulation of CWDE genes, CmCHI and CmGLU, as observed by qRT-PCR, leading to high chitinase and β-1,3-glucanase activities, as observed through enzyme assays. The results of SEM microscopy revealed that the effect of the crude enzymes of EAWP-treated muskmelon caused morphological changes in F. incarnatum mycelia. Furthermore, treatment with EAWPs preserved postharvest quality in muskmelon, including with regard to texture stiffness and total chlorophyll contents, compared to untreated muskmelon. These results demonstrate that the pretreatment of muskmelon with EAWPs suppresses the development of F. incarnatum in the early stage of infection by regulating gene expression of CWDEs and elevating the activities of CWDEs, while also maintaining postharvest muskmelon quality.