Isolation and Identification of Postharvest Pathogenic Fungi of Prune Fruits and Their Inhibition by LED Blue Light

Objective: The main pathogenic fungi causing post-harvest diseases of prune were isolated and identified, and the inhibitory effect of LED blue light (200±20 μmol·m⁻²·s⁻¹) on these pathogenic fungi was clarified, so as to provide a theoretical basis for the prevention and control of prune diseases during the post-harvest storage of prune fruits. Method: Pathogenic fungi were isolated and purified from prune fruits with natural onset of disease during post-harvest low-temperature storage, and combined with morphological observation, analysis of fungal rDNA internal transcribed spacer (ITS) and construction of phylogenetic tree, and back-joining validation of pathogenic strains, to clarify the main pathogenic fungal species responsible for post-harvest decay of prunes. LED blue light (200±20 μmol·m⁻²·s⁻¹) was used to irradiate the above isolated pathogenic fungi, and the inhibitory effect of LED blue light on the pathogenic fungi was clarified by observing the colony diameters of the pathogenic fungi combined with scanning electron microscopy. Result: A total of three strains of pathogenic fungi were isolated from post-harvest decayed prune fruits and identified as Penicillium crustosum, Alternaria alternata, and Botrytis cinerea. The results of LED blue light irradiation showed that 3 h of light per day could have an inhibitory effect on the growth of Penicillium crustosum and Botrytis cinerea, the growth of Botrytis cinerea could be completely inhibited when the daily light time reached 24 h. The effect of 12 h of light per day could be produced on Alternaria alternata. The inhibitory effect of LED blue light gradually strengthened with the increase of the light time per day on the three strains of fungi, and LED blue light could also destroy the mycelial structure of the three strains of pathogenic fungi, so that the mycelium appeared to a certain degree of wrinkled, collapsed, twisted, folded and other phenomena. Conclusion: Penicillium crustosum, Alternaria alternata and Botrytis cinerea can cause fungal diseases in prunes during postharvest refrigeration, and LED blue light has a good inhibitory effect on the three pathogenic fungal strains.