Effect of Lemon Balm Water Extract on Fusarium Wilt Control in Strawberry and Antifungal Properties of Secondary Metabolites

Abstract

In this study, the in vivo potential of lemon balm water extract on Fusarium wilt control in strawberry and the antifungal properties of secondary metabolites in the extract were investigated. Runner plants of strawberry (Fragaria × ananassa Duch., ‘Sachinoka’) were treated with water extracts (20%, w/v) of lemon balm (Melissa officinalis L.) and inoculated with Fusarium oxysporum f. sp. fragariae (Fof). Four weeks after Fof inoculation, lower disease incidence and indices in both shoots and roots were observed in lemon balm-treated plants. These effects could be attributed to reduced Fusarium populations due to the fungistasis and fungicidal effects induced by the extract in the rhizospheric soil. Consequently, dry weights of shoots and roots in the plants treated with lemon balm extracts were higher than those of the control. Based on the results of ultra performance liquid chromatography-tandem mass spectrometer (UPLC-MS/MS) analyses, rosmarinic acid was the metabolite with the highest concentration and was also the most stable metabolite in the water extract. In addition, the antifungal effect of rosmarinic acid against Fof was confirmed by in vitro tests. Therefore, water extracts of lemon balm could suppress Fusarium wilt in strawberry plants and rosmarinic acid was one of the key metabolites with antifungal properties present in the water extract.