Research may have found a simple, cost-effective solution for vine trunk diseases
Grapevine stem diseases, or GTDs, are the scourge of vineyard owners worldwide, and in 2012 were responsible for more than $1.5 billion in annual economic damage. While researchers have long known that a multitude of pathogenic fungi combine to gang up on vines, the mechanics of how these GTD-causing fungi work has remained a mystery.
Recently, an international cohort of researchers, led by the University of Massachusetts at Amherst, announced a previously unknown mechanism that is deployed by a group of pathogenic fungi working in concert that are responsible for the death of vines. Luckily, it looks like a fairly simple and cost-effective solution is on the horizon.
GTDs have been known to devastate up to 30% of the vines in a single vineyard each year and usually attack older, well-established vines. In California alone, annual GTD-related losses amount to 14% of the total value of wine grapes produced.
GTD-causing fungi usually enter the vine system through pruning wounds and, once established, develop a rotting canker that gradually grows, dissolving the woody part of the vine from the inside out. outdoors and killing the plant. Dissolving the tough cellulose and lignin structure that makes up woody plants isn’t easy, but a consortium of fungi has figured out how to do it, baffling scientists.
The missing ingredient is an understanding of what very small compounds produced by fungi actually do to vines.”
Barry Goodell, professor of microbiology at UMass Amherst, and lead author of the paper
In particular, Goodell and his colleagues and students at UMass Amherst, as well as collaborating scientists from the University of Florence in Italy, the University of Lorraine and the University of Haute-Alsace, both in France, and the University of Concepción in Chile, as well as vineyard owners in France and Italy, have discovered that some of the fungi responsible for GTD produce different types of small compounds that are released into the wood of the vine. One of these compounds is responsible for iron reduction. Normally we encounter iron as the chemical compound, Fe3+. Reduction of iron from Fe3+ to Fe2+ paves the way for nasty vine problems.
“But that’s not the whole story,” Goodell says. “We also found that there is another set of small compounds that are produced by other fungi in consortia, and these compounds are really good at producing hydrogen peroxide. When hydrogen peroxide meets iron reduced; BOOM! – the reaction releases a host of oxygen radicals that damage woody tissue causing an almost cancerous disease.”
In short, different fungi, each producing one of two types of small compounds needed for an extracellular bomb, figured out how to come together, mix their respective chemicals, and use them to blast through the cellulosic walls of grapevine cells. Once the cell walls are broken through, the fungi can feast on the sugar-rich liquid that was once the cell structure supporting vine growth.
Fortunately, there is a potential solution, which is so common that consumers probably eat it every morning with cereal: antioxidants and low-toxicity chelators. Often added to food products to preserve freshness, they also interrupt the production of reduced iron and hydrogen peroxide. They also scavenge oxygen radicals produced by fungi. “In addition,” Goodell points out, “there are select bacteria and fungi that produce these antioxidant and chelating compounds. Our research shows that we may be able to manage and stop TGDs through “biological control” treatments. “by increasing the natural presence of these antagonistic organisms on the vines.”
“Of course, there’s still work to be done,” Goodell says. “Vineyard pathologists need to test our research in the field, and other microbiologists will want to verify our work. But we already have colleagues in our wider team who do, and we believe this research represents a breakthrough in how we understand this devastating disease of vineyards and how to control this devastation.”
University of Massachusetts at Amherst
Perez-Gonzalez, G. et al. (2022) Oxygen radical-generating metabolites secreted by fungal consortia Eutypa and Esca: understanding the mechanisms underlying grapevine wood spoilage and pathogenesis. Frontiers in plant science. doi.org/10.3389/fpls.2022.921961.