In vitro and in vivo effectiveness of phenolic compounds for the control of postharvest gray mold of table grapes

As the natural antimicrobial metabolites, phenolic compounds were reported to be effective in the inhibition of phytopathogenic fungi, including the postharvest decay agents. However, comprehensive study on the biological activity of phenolic compounds and their application on controlling postharvest gray mold of table grapes is lacking. In this study, the antifungal effect of 18 natural or synthetic phenolic compounds purchased from commercial suppliers, including simple phenolic, phenolic acids, stilbenes and flavonoids, were determined on four gray mold strains by an in vitro agar dilution assay. Overall, seven phenolic compounds were effective on inhibiting B. cinerea growth and were selected to test their activity on conidial germination as well as in vivo application on grape berries. Pterostilbene showed the highest antifungal activity and greatly reduced the growth of the mycelia, caused hyphae deformation, suppressed conidial germination of B. cinerea, and completely inhibited the germination of conidia at the concentration of 50 mg L−1. Furthermore, treatment of grape berries with pterostilbene and piceatannol significantly reduced the disease incidence and severity. Our results demonstrate the antifungal activity of phenolic compounds and highlight their potentials as an alternative strategy in the control of postharvest gray mold of table grapes.