Submitted to: Australian Journal of Grape and Wine Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/12/2006
Publication Date: 7/1/2006
Citation: Lardner, R., Mahoney, N.E., Zanker, T., Molyneux, R.J., Scott, E. 2006. Secondary metabolite production by the fungal pathogen eutypa lata: analysis of extracts from grapevine cultures and detection of those metabolites in planta. Australian Journal of Grape and Wine Research. 12(2):107-114. Interpretive Summary: Dying arm disease is responsible for major losses in grapevine production worldwide, with losses of $260 million per year in California alone. The disease is caused by a fungus (Eutypa lata) that enters the plant through pruning wounds. Because the disease progresses slowly, it is difficult to identify vines that may be infected at an early stage. This research is designed to identify specific compounds produced by the fungus that can be used as markers for infection in the plant. Six compounds were commonly produced, of which one, named eutypinol, was present in the greatest amount. Grapevine plantlets contained eutypinol when treated with the fungus but the sap of mature vines did not contain any of the compounds, indicating that the toxic compounds are not transferred from the point of infection.
Technical Abstract: Eutypa dieback of grapevines is caused by the fungal pathogen Eutypa lata and reduces vineyard longevity worldwide. Early detection could reduce losses due to this disease, so our aim was to identify acetylenic phenol metabolites of E. lata that could prove suitable as chemical markers in an early diagnostic test for the pathogen. Accordingly, secondary metabolite production by 30 isolates of E. lata grown on media derived from canes of three grapevine cultivars was analysed using HPLC. Six metabolites, namely eutypinol, methyl eutypinol, eulatachromene, eutypine, 2-iso-propenyl-5-formylbenzofuran and eulatinol, were detected in culture filtrates. Most abundant were eutypinol and methyl eutypinol, produced by 97 and 83% of isolates, respectively. There was no apparent correlation between secondary metabolite production on media containing milled canes from the three cultivars of grapevine, and the field tolerance of these same cultivars to Eutypa dieback. When various other fungi commonly isolated from grapevine trunks in Australia were grown on milled cane, no secondary metabolites characteristic of E. lata were detected, suggesting such compounds are specific to E. lata. To examine the detection of secondary metabolites in planta, micropropagated grapevine plantlets were treated with purified or crude culture filtrates from nine isolates of E. lata grown on malt yeast broth. Various secondary metabolites were identified in treated plantlets, however, no single compound was detected consistently. Eutypinol was detected in micropropagated grapevine plantlets inoculated with mycelium of E. lata, however, no metabolites were detected in the sap of vines which had been artificially inoculated with the pathogen.