Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/11/2005
Publication Date: 10/19/2005
Citation: Mahoney, N.E., Molyneux, R.J., Smith, L.R., Schoch, T.K., Rolshausen, P.E. 2005. Dying-arm disease in grapevines: diagnosis of eutypa infection by metabolite analysis. Journal of Agricultural and Food Chemistry.53:8148-8155. 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. Three compounds were commonly produced, of which one, named eutypinol, was present in the greatest amount. This compound could be detected when sections of grapevine trunk were placed in water, allowing the fungus to grow, if present. In trunk sections without infection, no eutypinol was produced. This shows that the test can be used to detect the fungus in grapevines, even when no signs of infection are present
Technical Abstract: Dying arm disease in grapevines, produced by infection with the ascomycete Eutypa lata, is responsible for major production losses in vineyards. Dieback of the shoots and cordon is believed to be due to acetylenic phenol metabolites produced by the fungus. In order to identify specific metabolites that could potentially be used for diagnosis of infection, eight Eutypa strains were grown in vitro on hot water extracts of susceptible and tolerant grape varieties. HPLC analysis showed that eutypinol was consistently produced in large amounts, together with smaller amounts of methyleutypinol and eulatachromene; eutypine, the putative toxin, was produced solely on Sauvignon Blanc extract and then only in barely detectable amounts. When E. lata strains isolated from Cabernet Sauvignon and Merlot were grown on identical media, the amounts of metabolites produced differed significantly between strains but the pattern of metabolites was quite similar, with eutypinol again predominating. The consistent production of eutypinol indicated that this was the most suitable metabolite for which to analyze in order to diagnose the presence of E. lata. Extraction and analysis of grapevine tissues exhibiting symptoms of dieback failed to show the presence of any metabolites. However, when infected cordon sections were placed in water and cultured for 5 days, eutypinol was readily detected in the aqueous solution; metabolites were not produced from uninfected tissue. This provides a method for detection of infected tissue and indicates that the toxic metabolites react at the point of production, disrupting the vascular structure and inhibiting transport of nutrients, rather than being translocated to tissues that exhibit symptoms.