Eutypa dieback: development of early diagnostic techniques

Eutypa dieback, caused by the fungus Eutypa lata, is a major threat to the sustainability and productivity of vineyards throughout the world. A primary need is to develop non-destructive techniques that will enable early detection of dieback before the pathogen has spread extensively through the grapevine. The production of secondary metabolites by 11 strains of E. lata, originating in Australia, America, New Zealand and Europe was analyzed using high performance liquid chromatography. A range of acetylenic phenol metabolites was detected and production was strongly influenced by both strain of fungus and type of media. The most abundant compound was eutypinol, structurally related to eutypine, the supposed phytotoxin, and was produced by 9 of the 11 strains examined, whereas eutypine was produced by only 4 strains. In order to determine the phytotoxicity of secondary metabolites produced by individual strains of the fungus, the purified culture filtrates containing all metabolites extracted from each strain were bioassayed on Cabernet Sauvignon leaf discs. Ten strains of E. lata produced culture filtrates that were toxic towards the leaf discs. The results indicate that phytotoxicity is the result of a suite of compounds, rather than the single compound, eutypine