The Role of Low-Molecular Weight Fungal Metabolites in Eutypa Dieback Grapevine Trunk Disease

This project focuses on understanding the fundamental chemistries that grapevine trunk disease fungi causing Eutypa canker and dieback employ in infecting and causing damage to grapevines. We will also develop treatments for GTDs by blocking the chemistries used by the pathogenic fungi. As part of this two-year project we will also disseminate our findings on both GTD causal systems and the treatments we develop to vineyard owners/managers and other interested parties. Our three Objectives for the two-year project are:
A) To better understand the role of iron-binding compounds produced by the mixed-consortia fungi involved in Eutypa dieback, with particular focus on how these compounds generate hydroxyl radicals – the most damaging form of ‘free radical’ found in biological systems – which we propose leads to stem/wood necrosis.
B) To use our enhanced understanding of Eutypa dieback in Year 2 of this research to develop treatments and management strategies for the control of Eutypa GTD.
C) To disseminate and interpret our research results to vineyards personnel to allow a better practical understanding of how Eutypa dieback chemistries function in causing the disease, and also to disseminate results of the treatment systems we will be designing to counteract the chemistries of the iron-binding compounds produced by Eutypa-consortia fungi.

We currently have been able to conduct research on the project for only 6 months, because of a funding start in June of 2019, and the time needed to ramp-up equipment and recruit a graduate student with appropriate background for the project. To date we have been able to grow three Eutypa consortia fungi under conditions of low nutrients and low iron, and demonstrate that these fungi will produce low molecular weight compounds iron-binding compounds. To produce these compounds, which have been shown to be capable of generating highly damaging hydroxyl radicals, it was necessary to simulate the low-iron and low nutrient condition inside the grapevine trunk. This has not been demonstrated previously because prior research on ironbinding compounds from these fungi was conducted using artificial media containing conventional laboratory media containing high sugar and high iron. Continuing in Year 1, we will chemically characterize the compounds and conduct assays for redox-cycling and hydroxyl radical generation. Our preliminary evidence so far indicates that several of the isolated compounds have these important properties, and thus they are ideal candidates for GTD pathogenic factors. We are also working currently with grapevine wood block assays to investigate soft rot activity as part of the pathogenicity process. These investigations are important because they provide us with targets for developing the chelating/antioxidant treatments that are the focus of our Year 2 research on controlling GTD fungi. Once these treatments have been developed and successfully tested in the lab, we are already preparing to move them into test in experimental vineyard tests we are currently developing this spring as an extension of this project. Dissemination of our results and outreach activities will continue throughout the project period.