Effect of pulsed light on postharvest disease control-related metabolomic variation in melon (Cucumis melo) artificially inoculated with Fusarium pallidoroseum

Pulsed light, as a postharvest technology, is an alternative to traditional fungicides, and can be used on a wide variety of fruit and vegetables for sanitization or pathogen control. In addition to these applications, other effects also are detected in vegetal cells, including changes in metabolism and production of secondary metabolites, which directly affect disease control response mechanisms. This study aimed to evaluate the possible applications of pulsed ultraviolet light in controlling postharvest rot, mainly caused by Fusarium pallidoroseum in yellow melon Goldex, in natura, and its implications in the disease control as a function of metabolomic expression to effect fungicidal or fungistatic. The dose of pulsed light (PL) that inhibited F. pallidoroseum growth in melons (Cucumis melo var. Spanish) was 9 KJ m-2. Ultra performance liquid chromatography (UPLC) coupled to a quadrupole time-of-flight (QTOF) mass analyzer identified 12 compounds based on the MS/MS fragmentation patterns. Chemometric analysis by Principal Components Analysis (PCA) and Orthogonal Partial Least Squared Discriminant Analysis (OPLS-DA and S-plot) were used to evaluate the changes in fruit metabolism. PL technology provided protection against postharvest disease in melons, directly inhibiting the growth of F. pallidoroseum through upregulation of specific fruit biomarkers such as pipecolic acid (11), saponarin (7), and orientin (3), which acted as major markers for the defense system against pathogens. PL can thus be proposed as a postharvest technology to avoid chemical fungicides and may be applied to reduce the decay of melon quality during its export and storage.