Light-emitting Diode Blue Light Alters the Ability of Penicillium digitatum to Infect Citrus Fruits

Penicillium digitatum (Pers.:Fr.) Sacc. is the main fungus causing postharvest losses in citrus fruits. Previous work showed the potential of LED blue light (LBL) in controlling P. digitatum growth. Here, we have investigated whether LBL alters the ability of this fungus to infect citrus fruits. Before fruit infection, Petri plates inoculated with the same conidia concentration were held under darkness (control) or LBL (100 μmol m^-2 s^-1 ) for 8 d (continuous light), or were treated with the same LBL for 3 d and then shifted to darkness for 5 d (non-continuous light). Spores from cultures exposed to continuous light showed very low capacity to germinate (1.8% respect to control) but a high viability and a similar morphology and ability to infect the fruits than spores from control cultures. The number of spores produced in plates exposed to non-continuous light was slightly lower than in control plates, but they showed much lower viability and lower capacity to infect the fruits. This effect was more likely related to aberrant morphology of spores, which formed aggregates, than to its metabolic activity or its ability to produce ethylene that might contribute to destroy natural defense barriers from the fruit.