Phytotoxic secondary metabolites produced by Neofusicoccum australe, a pathogen involved in a grapevine trunk dieback in Italy

Fungal trunk diseases have become a growing threat to viticulture throughout the world. Recent studies revealed that species in the Botryosphaeriaceae family include some of the main pathogens involved in grapevine canker, dieback and decline in most grape-growing regions of Northern and Southern hemispheres. A field survey conducted in a grape-growing area located in northern Sardinia (Italy) detected Neofusicoccum australe as one of the main fungal pathogens associated with grapevine cordon dieback. The nature and appearance of wood symptoms caused by this pathogen suggested that phytotoxic metabolites could be involved in the host-pathogen interaction. To our knowledge, no data are available in the literature on the production of phytotoxic metabolites by N. australe strains involved in grapevine trunk diseases. Thus, a highly virulent isolate of N. australe was examined for its ability to produce in vitro phytotoxic secondary metabolites. For this purpose, the fungus was grown in liquid culture. The culture filtrate and the corresponding organic extract showed to be highly phytotoxic when assayed on host and non-host plants by cutting and leaf puncture assay. This communication reports the chemical and biological characterization of phytotoxic metabolites produced in liquid culture by N. australe isolated in Sardinia from grapevine and other host plants. Their role in the disease will be discussed.