Inhibition of Fungi from Diseased Grape by Syringomycin E-Rhamnolipid Mixture

Fungal infections of vineyard grapes compromise the yield and sensory properties of wines. Consequently, there is a need for more effective fungal control measures. The aim of this work was to evaluate the potential of a novel lipopeptide fungicidal formulation to control these diseases. A mixture of rhamnolipids (RLs) and the lipodepsinonapeptide syringomycin E (SRE) showed greater inhibitory activities than SRE alone against fungi isolated from grape berries and stems of a heavily infected vineyard in Louisiana. The fungal species tested were Aspergillus japonicus, Cladosporium cladosporioides , Curvularia brachyspora , Greeneria uvicola, Nigrospora sphaerica, Trichoderma sp., Penicillium sclerotiorum, and P. thomii . Exposure to SRE resulted in 50% killing of germinating conidia of all these fungal species at concentrations between 0.75 and 3 μM and the SRE + RL mixture gave 50% killing between 0.75 and 1 μM SRE. Nongerminated conidia of only C. brachyspora were killed by SRE alone or SRE + RLs (both giving 50% killing at