Synergistic Effects of Resveratrol and Pyrimethanil against Botrytis cinerea on Grape
Botrytis cinerea is the pathogen of gray mold disease affecting a wide range of plant hosts, with consequential economic losses worldwide. The increased frequency of fungicide resistance of the pathogen challenges its disease management, and thus the development of alternative control strategies are urgently required. In this study, we showed excellent synergistic interactions between resveratrol and pyrimethanil. Significant synergistic values were recorded by the two-drug combination on the
... ppression of mycelial growth and conidia germination of B. cinerea. The combination of resveratrol and pyrimethanil caused malformation of mycelia. Moreover, the inoculation assay was conducted on table grape and consistent synergistic suppression of the two-drug combination was found in vivo. Our findings first revealed that the combination of resveratrol and pyrimethanil has synergistic effects against resistant B. cinerea and support the potential use of resveratrol as a promising adjuvant on the control of gray mold. Molecules 2018, 23, 1455 2 of 12 antiviral activities  as well as growth modulatory effects on various organisms . Moreover, resveratrol displays significant antifungal effects toward several plant pathogens [22-24], and our previous study indicated the excellent efficacy of resveratrol on the control of gray mold of table grape . Various pharmacological and biological properties of resveratrol have made it an attractive candidate for the plant disease control. Combination therapy of two or more antibiotics has emerged as an attempt to prevent or delay the emergence of resistance, enhance the activity of antibiotics and reduce the application amounts of fungicides [26, 27] . Plant phenolics, as natural secondary metabolites, have been reported to enhance the activity of classical antibiotics and represent promising adjuvants of antibacterial and antifungal drugs    . To our knowledge, however, no studies have been conducted on the synergistic effects of phenolic compounds in combination with fungicides against B. cinerea. In this study, the antifungal activity of selected phenolic resveratrol alone and in combination with conventional fungicide pyrimethanil against B. cinerea was evaluated by microdilution method. Additionally, their synergistic effects on mycelial growth and conidia germination of B. cinerea in vitro, and the suppression of table grape gray mold disease were also explored.