Fungi and oomycetes involved in the Tamarix gallica decline in the Venice lagoon

Plant pathogens are an important subject for research. There have been numerous cases of pathogens causing incredible environmental and economic damage over the years, thus improving the knowledge of presence and abundance of pathogens is helpful for forest managers, agriculture and landowners alike. With understanding of pathogen distribution, strategies can be planned accordingly. This study provides research about pathogens associated with Tamarix gallica found in the Venice lagoon environment. The Venice lagoon has been a historical port and touristic centre of Europe for centuries which could be an important factor in bringing pathogens to this environment. Whilst lagoon environments provide a habitat that is dynamic, with changing characteristics that can cause stress to a plant. In numerous sites around the lagoon, we report about the fungal and oomycete species found on Tamarix gallica. Pathogens in a lagoon environment have not been widely studied but it is well known that many fungal and oomycete species are capable of surviving in saltwater environments. Plants showcasing dieback symptoms were sampled along with systematic random samples of soil to analyse DNA and report about which pathogens were present. Laboratory analysis allowed us to obtain 13 varieties of fungi in pure culture (Alternaria, Botryosphaeria dothidea, Bjerkandera adusta, Cytospora unicolaris, Diplodia mutila, Diaporthe foeniculina, Dothiorella Iberica, Eutypa consobrina, Neofusicoccum australe, Neofusicoccum cryptoaustrale, Neofusicoccum luteum, Neofusicoccum parvum and Peniophora tamaricicola) and 6 species belonging to the Oomycete class (Globiporangium perplexum, Halophytophthora thermoambigua, Phytophthora inundata, Phytophthora multivora, Phytophthora plurivora, Pythium contiguanum). Neofusicoccum parvum (Botryosphaeriaceae) was by far the most widespread of pathogens isolated from the study whilst also being one of the most aggressive in pathogenicity tests, highlighting the threat of this species to Tamarix gallica within the lagoon. This, alongside the three other Neofusicoccum species isolated formed the largest lesions in the pathogenicity tests when confirming Koch’s postulates. The results showed a strong diversity of phytopathogenic species on Tamarix gallica in a small study area within the Venice lagoon including multiple new host-pathogen associations.