Antifungal activity and application of Neurospora sitophila Y-4 against postharvest Penicillium italicum of Citrus reticulata 'Shiyue Ju' via 3-penten-2-one

Citrus reticulata 'Shiyue Ju' are prone to fungal infections because of their high maturity, water content, and remote cultivation locations. Chemical control, though effective, leaves fruit residues that endanger health and the environment. Endophytic VOCs potently inhibit pathogens with high efficacy, low cost, and minimal ecological impact, positioning them as promising natural post-harvest preservatives. In this study, we isolated the pathogenic fungus ( Penicillium italicum Q-1) from rotting Citrus reticulata 'Shiyue Ju' and used Q-1 as the test strain to screen for endophytic fungi Y-4 isolated from healthy Citrus reticulata 'Shiyue Ju' that can produce VOCs with strong antagonistic activity. We analyzed the VOC components and screened for the highly bactericidal activity compound 3-pentene-2-one,exhibiting complete (100 %) growth inhibition at 4 μL/L. We also investigated the inhibitory activity and mechanisms of action of the VOCs and antifungal compounds. The results indicated that the VOCs produced by Y-4 and 3-pentene-2-one could inhibit the growth and reproduction of the pathogenic fungus, primarily by disrupting the normal morphological structure of hyphae and spores and damaging the integrity of the cell membrane. Furthermore, 3-pentene-2-one at appropriate concentrations can inhibit the spread of pathogenic fungi on Citrus reticulata 'Shiyue Ju' and effectively delay the decline in fruit quality. These findings indicate that 3-pentene-2-one is a powerful tool for controlling P. italicum and provides a theoretical basis for post-harvest disease management of Citrus reticulata 'Shiyue Ju' .