Application of UV-B Light and Low-Toxicity Compounds to Prevent Postharvest Spoilage on Lemons

Green and blue molds and sour rot, caused by Penicillium digitatum, P. italicum, and Geotrichum citri-aurantii, are postharvest diseases which represent an important economic issue in lemon production. Conventionally, their control involves the intensive use of synthetic fungicides, leading to the emergence of resistant strains and harmful residue accumulation on fruits. Present work explores the application of UV-B radiation (UVBr) and its combination with polyhexamethylene guanidine (PHMG) or natamycin on lemons as alternative strategy to manage fungal postharvest diseases caused by fungicide-sensitive and resistant local isolates. UVBr applied in vitro inhibited mycelial growth and conidia viability of all pathogens at the highest assayed dose (5.2 J cm-2). Light preventive treatment applied on lemons with a non-fungicidal and non-phytotoxic UVBr dose of 0.1 J cm-2 significantly reduced disease incidences by approximately 30 to 55%, along with reducing disease severities. Both PHMG and natamycin effectively reduced disease incidences caused by all tested pathogens, with a notable synergistic effect when combining UVBr with natamycin against Penicillium-sensitive isolates. None of these treatments had adverse effects on fruit quality. Importantly, preventive UVBr treatment enabled lemons to maintain H2O2 levels at the wound site in the presence of P. digitatum, which typically suppresses H2O2 production in the host tissue. In conclusion, findings suggest that UVBr and its combination with low-toxicity compounds offer a promising environment-friendly alternative for controlling postharvest lemon diseases caused by both fungicide-sensitive and resistant pathogens.

Automated summary

This study examines the use of UV-B radiation and its combination with low-toxicity compounds as an alternative strategy to control postharvest diseases in lemons. The results show that the combination of UVBr and natamycin effectively reduces disease incidences without adverse effects on fruit quality.