Phytotoxic Metabolites Produced by Fungi Involved in Grapevine Trunk Diseases: Progress, Challenges, and Opportunities

Abstract

Grapevine trunk diseases (GTDs), caused by fungal pathogens, are a serious threat to vineyards worldwide, causing significant yield and economic loss. To date, curative methods are not available for GTDs, and the relationship between the pathogen and symptom expression is poorly understood. Several plant pathologists, molecular biologists, and chemists have been investigating different aspects of the pathogenicity, biochemistry, and chemical ecology of the fungal species involved in GTDs. Many studies have been conducted to investigate virulence factors, including the chemical characterization of phytotoxic metabolites (PMs) that assist fungi in invading and colonizing crops such as grapevines. Moreover, multidisciplinary studies on their role in pathogenicity, symptom development, and plant-pathogen interactions have also been carried out. The aim of the present review is to provide an illustrative overview of the biological and chemical characterization of PMs produced by fungi involved in Eutypa dieback, Esca complex, and Botryosphaeria dieback. Moreover, multidisciplinary investigations on host-pathogen interactions, including those using cutting-edge Omics techniques, will also be reviewed and discussed. Finally, challenges and opportunities in the role of PMs for reliable field diagnosis and control of GTDs in vineyards will also be explored.

Comparative pangenomic insights into the distinct evolution of virulence factors among grapevine trunk pathogens

“…E. lata, for example, breaks down cellulose and other cell-wall glycans, also secreting oxidases that may degrade wall-bound lignin in the wood (8). Various secondary metabolites with phytotoxic properties, such as eutypine, eutypinol, scytalone, isosclerone, mellein, tyrosol, and others, have been detected in the secretomes of pathogens causing Eutypa, Esca, and Botryosphaeria dieback (9)(10)(11)(12). Even if the precise mode of action of these molecules is not fully understood, it is known that fungal toxins can harm plant cells by interfering with enzymatic reactions, cellular transport, and causing damage to cell membranes (6,13).…”

Biocontrol of almond canker diseases caused by Botryosphaeriaceae fungi

“…In addition, Botryosphaeriaceae fungi are able to produce phytotoxic metabolites that assist fungi in invading and colonizing the host plant. 22 Disease symptoms consist of trunk and branch cankers, extensive gummosis, discoloration and necrosis of internal tissues, plant dieback and, occasionally, plant death. 23 The main external sources of inoculum consist of neighboring crops and ornamentals, which are alternative hosts for Botryosphaeriaceae species, 24 as well as the plant propagation materials from nurseries.…”

“…These fungi can colonize the xylem vessels reducing the flow of nutrients and releasing hydrolytic enzymes which degrade the xylem vessel cell walls. In addition, Botryosphaeriaceae fungi are able to produce phytotoxic metabolites that assist fungi in invading and colonizing the host plant 22 . Disease symptoms consist of trunk and branch cankers, extensive gummosis, discoloration and necrosis of internal tissues, plant dieback and, occasionally, plant death 23 …”