Esca Disease on Grapevine Plants – grapevine trunk diseases (GTD)
A: Phaeomoniella chlamydospora CFP mutant/mycelium
B: Phaeomoniella chlamydospora and Vitis vinifera callus culture
C: Vineyard in Freiburg (Breisgau)
Introduction
Esca, Eutypa dieback and botryosphaeria dieback are three significant grapevine trunk diseases that involve one or several xylem-inhabiting fungi. Phaeomoniella chlamydospora, Phaeoacremonium minimum, Eutypa lata, Fomitiporia mediterranea and several members of the Botryosphaeriaceae are the main species that have been associated with these diseases worldwide.
These three diseases, described as early as the end of the 19th century, mainly attack the perennial organs of the grapevine (Vitis vinifera), leading to leaf and berry symptoms and death. As a result, grapevine trunk diseases are detrimental to the resilience of the wine-growing heritage. Moreover, no grapevine taxa, either cultivated or wild, are known to be resistant to trunk diseases. Over the past few decades, the frequency of symptoms of these diseases has increased considerably worldwide. For example, disease incidence values that were estimated over 4 years in approximately 700 French vineyards, including affected trunk disease and dead plants, showed that approximately 10% of productive plants were affected. Sodium arsenite was the sole treatment that had a potential effect against these diseases, especially esca, but it has been prohibited, beginning in 2000, because of its toxicity both to the environment and to humans. The lack of strategies for fighting the diseases, new pruning practices and the necessary protection of the environment could exacerbate the situation.
Because these pathogens have never been isolated from the leaves of infected plants, it was hypothesized that the leaf and berry symptoms are actually caused by extracellular compounds produced by fungi in the discolored woody tissues of the trunk and which are then translocated to the leaves through the transpiration stream.
Although results of many research studies have led to esca being defined as a complex of diseases (esca disease complex), the term ‘esca’ is still commonly used to refer to most of the diseases forming the complex. The characterization of grapevine trunk diseases is crucial, not only for studying their phytotoxic properties, but also because their detection in grapevines represents a useful tool for an early diagnosis of trunk diseases. Numerous studies have dealt with various aspects of these diseases and the fungi associated with them (i.e. epidemiology, pathogenicity and host–pathogen interactions), but the causes of symptom development remain elusive.
A: Dasyscyphus sp. on a grapevine trunk
B: Antagonist test: Fomitiporia mediterranea and a inhibiting bacterial strain on minimal medium
C: Fungal diversity: endophytic isolates from a grapevine plant
Esca Research at the IBWF
Screening for fungal Antagonistic Biocontrol Agents
Using various methods:
Agar plate test
96-well plate extract screening
Vitis shoot assay
Isolation and Characterisation of fungal secondary metabolites and phytotoxic substances
Identification of drug targets in Esca associated fungi to generate and provide new methods to control grapevine trunk diseases Generation of KO and insertion mutants and establishing of new molecular methods suitable for Esca trunk disease pathogens
Interaction studies with fungal pathogens and Vitis vinifera callus cultures
Action participant at the Cost Action FA1303: Sustainable control of grapevine trunk diseases – http://managtd.eu/en/
References
Fischer, J., Compant, S., Pierron, R.J., Gorfer, M., Jacques, A., Thines, E. and Berger, H., 2016. Differing Alterations of Two Esca Associated Fungi, Phaeoacremonium aleophilum and Phaeomoniella chlamydospora on Transcriptomic Level, to Co-Cultured Vitis vinifera L. calli. PloS one, 11(9), p.e0163344.