Grapevine trunk diseases, or GTD, represent one of the major problems faced by viticulturists worldwide, as they are responsible for economic damages exceeding 1.5 billion dollars annually.
It has been known for a long time that a wide range of pathogenic fungi are involved in this disease and that they act simultaneously attacking grapevines, but the mechanisms of action of these fungi remain a mystery.
Recently, an international team of researchers led by the University of Massachusetts Amherst has uncovered a hitherto unknown mechanism that is implemented by a group of pathogenic fungi that act together and are responsible for the death of grapevines.
The fungi that cause GTD generally enter the vine system through pruning wounds and, once established, cause a rot that gradually spreads, destroying the woody part of the vine from the inside out and killing the plant. Destroying the tough cellulose and lignin structure that forms the woody part of plants is no easy task, but one set of fungi has figured out how to do it. The key, according to the authors of this work, lies in understanding what exactly it is that the tiny compounds produced by the fungi cause in the vines.
This research work by UMass Amherst in collaboration with the University of Florence in Italy, Université de Lorraine and Université de Haute-Alsace in France, and Universidad de Concepción in Chile has found that some of the fungi responsible for GTD produce different types of small compounds that are released into grapevine wood. One of these compounds preferentially reduces iron, while others are involved in the redox cycle, leading to the formation of hydrogen peroxide.
When hydrogen peroxide meets reduced iron, the reaction releases a large amount of highly reactive hydroxyl radicals. This mechanism could be involved in the causal mechanism associated with the decay/necrosis of trunk wood in these diseases.
According to the authors, there is a potential solution: low-toxicity antioxidants and chelators that scavenge the oxygen radicals produced by the fungi. Certain bacteria and fungi are capable of producing these antioxidant and chelating compounds. This work shows that it is possible to control and stop GTD through biological control treatments by increasing the natural presence of these antagonistic organisms in grapevines.
These results still need to be studied and demonstrated in the field, but they represent a breakthrough in the understanding of the mechanisms of action of this devastating disease.
Reference article.
Gabriel Perez-Gonzalez et al, Oxygen Radical-Generating Metabolites Secreted by Eutypa and Esca Fungal Consortia: Understanding the Mechanisms Behind Grapevine Wood Deterioration and Pathogenesis, Frontiers in Plant Science (2022). DOI: 10.3389/fpls.2022.921961
