title: Saprolegnia strains isolated from river insects and amphipods are broad spectrum pathogens.
abstract: Saprolegnia species are destructive pathogens to many aquatic organisms and are found in most parts of the world. Reports based on phylogenetic analysis suggest that Saprolegnia strains isolated from aquatic animals such as crustaceans and frogs are close to Saprolegnia strains isolated from infected fish or fish eggs and vice versa. However, it has often been assumed that host specificity occurs for each individual isolate or strain. Here we demonstrate that Saprolegnia spp. can have multiple hosts and are thus capable of infecting different aquatic organisms. Saprolegnia delica, Saprolegnia hypogyna, and 2 strains of Saprolegnia diclina were isolated from aquatic insects and amphipods while S. delica, Saprolegnia ferax, Pythium pachycaule, and a Pythium sp. were isolated from the water of a medium to fast flowing river. The ITS region of the rRNA gene was sequenced for all isolates. In challenge experiments, all four isolates from insects were found to be highly pathogenic to eggs of Atlantic salmon (Salmo salar) and embryos of the African clawed frog (Xenopus laevis). We found that Saprolegnia spp. isolated from salmon eggs were also able to successfully establish infection in nymphs of stonefly (Perla bipunctata) and embryos of X. laevis). These results suggest that Saprolegnia spp. are capable of infecting multiple hosts, which may give them an advantage during seasonal variation in their natural environments.
authors.affiliation: Aberdeen Oomycete Laboratory, University of Aberdeen, School of Medical Sciences, Foresterhill, Aberdeen AB25 2ZD, UK.
authors.forename: Mohammad Nasif
authors.initials: MN
authors.lastname: Sarowar
authors.forename: Albert Hendrik
authors.initials: AH
authors.lastname: van den Berg
authors.forename: Debbie
authors.initials: D
authors.lastname: McLaggan
authors.forename: Mark R
authors.initials: MR
authors.lastname: Young
authors.forename: Pieter
authors.initials: P
authors.lastname: van West
mesh_terms: D033304:Amphipoda / Q000382:microbiology*; D000818:Animals; D016000:Cluster Analysis; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000737:chemistry / Q000235:genetics; D058507:Host Specificity; D007313:Insecta / Q000382:microbiology*; D008969:Molecular Sequence Data; D010802:Phylogeny; D045483:Rivers / Q000382:microbiology*; D044762:Saprolegnia / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D017422:Sequence Analysis, DNA
chemical_list: D004271:DNA, Fungal; D021903:DNA, Ribosomal Spacer
keywords: Aquatic insects; Multiple hosts; Salmo salar; Saprolegniosis; Xenopus laevis