Antifungal efficacy of LEDs against major postharvest pathogens of litchi fruit in vitro and in vivo

Abstract

Postharvest fruit diseases in litchi (Litchi chinensis Sonn.) caused by fungi are one of the major problems in the fruit industry. Light-emitting diodes (LEDs) technology is a promising alternative to fungicides to control postharvest fungal decay. This study aimed to evaluate the antifungal potential of LEDs against postharvest pathogens Geotrichum candidum and Fusarium sp. isolated from litchi fruit in vitro and in vivo. Results showed that violet light (410–420 nm) was more effective at inhibiting both fungi than other wavelengths of LED. The inhibition effect was dose-dependent, with spore germination completely inhibited and mycelial growth inhibited by about 65–79% when LED illumination for 10 h. In vivo assays demonstrated that LED reduced the population of G. candidum and Fusarium sp. by more than 2 log CFU/g (∼99%) on litchi fruit. However, different surface characteristics of the fruit produced different shielding effects on this technology. In addition, there were also species specificity in the inactivation effect, with Fusarium sp. being more resistant to LED than G. candidum. Notably, the antifungal efficacy at 25 °C was greater than at lower temperatures. These results demonstrate that LED holds great potential as a postharvest preservation technology for reducing the risk of fruit spoilage. The efficacy of treatment could be associated with multiple factors (e.g., wavelengths, exposure duration, temperature, fungal species, and fruit surface characteristics) and therefore needs to be well considered when applying the technique in food systems.