Multiple Halophytophthora spp. and Phytophthora spp. including P. gemini, P. inundata, and P. chesapeakensis sp. nov. isolated from the seagrass Zostera marina in the Northern Hemisphere

A plethora of oomycetes was isolated mostly from Zostera marina but also from other halophilic plants originating from several locations including the Wadden Sea, Limfjord (Denmark), the Dutch Delta area (the Netherlands), Thau lagoon (France), Lindholmen (Sweden) and Chesapeake Bay (Virginia, U.S.). Based on ITS sequences, seven different groups could be distinguished. The largest group was assigned to Phytophthora gemini (Germany, Sweden, the Netherlands, U.S.). The CoxI sequences of all P. gemini strains were identical indicating that P. gemini is probably an invasive species in the Wadden Sea. A second group was identified as P. inundata (the Netherlands, Denmark), that was also isolated from the halophilic plants Aster tripolium and Salicornia europaea. Four strains, originating from Chesapeake Bay clustered in a monophyletic clade with high bootstrap support at the ITS as well as the CoxI loci. They are phylogenetically closely related to P. gemini and are considered to represent a new species described here as Phytophthora chesapeakensis sp. nov. In addition, Salisapilea sapeloensis was isolated from Zostera noltii. Eleven other strains belonging to three unidentified taxa, originating from the Wadden Sea, the Dutch Delta area and Thau lagoon, clustered each in a monophyletic clade with high bootstrap support at the ITS locus, including Halophytophthora vesicula, the type species of the genus Halophytophthora. Hence, these strains were considered to belong to the Halophytophthora sensu stricto group and probably represent three new Halophytophthora species, informally designated here as Halophytophthora sp-1, Halophytophthora sp-3 and Halophytophthora sp-4 sensu Nigrelli and Thines. Halophytophthora sp-2 was not detected in this study. In addition, P. gemini and Halophytophthora sp-3 were obtained by baiting from locations in the Wadden Sea and Halophytophthora sp-1 was obtained by baiting from the Delta area.