The morphology, behaviour and molecular phylogeny of Phytophthora taxon Salixsoil and its redesignation as Phytophthora lacustris sp. nov.

摘要

Since its first isolation from Salix roots in 1972, isolates of a sexually sterile Phytophthora species have been obtained frequently\udfrom wet or riparian habitats worldwide and have also been isolated from roots of Alnus and Prunus spp. Although\udoriginally assigned to Phytophthora gonapodyides on morphological grounds, it was recognized that these isolates, informally\udnamed P. taxon Salixsoil, might represent a separate lineage within ITS Clade 6. Based on phylogenetic analyses and\udcomparisons of morphology, growth-temperature relationships and pathogenicity, this taxon is formally described here as\udPhytophthora lacustris sp. nov. Isolates of P. lacustris form a clearly resolved cluster in both ITS and mitochondrial cox1\udphylogenies, basal to most other Clade 6 taxa. Phytophthora lacustris shares several unusual behavioural properties with\udother aquatic Clade 6 species, such as sexual sterility and tolerance of high temperatures, that have been suggested as adaptations\udto riparian conditions. It appears to be widespread in Europe and has also been detected in Australia, New Zealand\udand the USA. Itwas shown to be weakly or moderately aggressive on inoculation to Alnus, Prunus and Salix. The extent of\udP. lacustris’ activity as a saprotroph in plant debris in water and as an opportunistic pathogen in riparian habitats needs further\udinvestigation. Its pathogenic potential to cultivated fruit trees also deserves attention because P. lacustris has apparently\udbeen introduced into the nursery trade.