|De Lucca Ii, Anthony|
Submitted to: American Journal of Enology and Viticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/17/2009
Publication Date: 3/10/2010
Citation: Takemoto, J.Y., Bensaci, M., De Lucca II, A.J., Cleveland, T.E., Gandhi, N.R., Skebba, V. 2010. Inhibition of fungi from diseased grape by syringomycin E-rhamnolipid mixture. American Journal of Enology and Viticulture. 61(1):120-124. Interpretive Summary: Syringomycin E and rhamnolipid are naturally produced, environmentally safe, antimicrobial agents. In this study we isolated members of seven fungal genera (“families” of fungi) from diseased grapes in a local vineyard. One of these fungi, Greeneria uvicola, is a primary pathogen of grapes while the remaining isolates, Aspergillus japonicus, Cladosporium cladosporioides, Curvularia brachyspora, Nigrospora sphaerica, Penicillium thomii and Penicillium sclerotiorum. Members of the Aspergillus, Penicillium and Cladosporium genera are known to cause rot of grape berries. In our laboratory studies, a combination of these two compounds showed significant lethality against these fungi at concentrations less than 50 parts per billion against the isolated fungi. These concentrations were significantly more lethal to the fungi than syringomycin E alone. The data indicates that, in combination, syringomycin E and rhamnolipid could protect grapes in vineyards against fungal infection.
Technical Abstract: Fungal infections of vineyard grapes compromise the yield and organoleptic properties of wines, and there is a need for more effective fungal control measures. The aim of the present work is to evaluate the potential of a novel lipopeptide fungicidal formulation to control these diseases. A mixture of rhamnolipids (RLs) and the lipodepsinonapeptide syringomycin E (SYRE) showed greater inhibitory activities than SYRE 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. SYRE gave 50% killing of germinating conidia of all these fungal species at concentrations between 0.75 and 3 µM and the SYRE + RL mixture gave 50% killing between 0.75 and 1 µM SYRE. Non-germinated conidia of C. brachyspora, but not of the other fungi, were killed by SYRE alone or SYRE + RLs (both giving 50% killing at < 1 µM SYRE). The RLs alone did not affect the growth of either germinating or non-germinated conidia of these fungi. These results demonstrate the strong and broad fungicidal properties of SYRE and show that when mixed with RLs, it is even more lethal to a wide range of grape-associated fungi when in the germination stage.