Saprolegnia molecular phylogeny among farmed teleosts in Nova Scotia, Canada

• Published in: Journal of Fish Diseases
• Main Authors: Sarowar, Mohammad Nasif, Cusack, Roland, Duston, James
• Other Authors: Nova Scotia Department of Fisheries and Aquaculture
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2019
• Subjects: Arctic charr; Atlantic salmon; Salmo salar; Salvelinus alpinus
• Online Access: http://dx.doi.org/10.1111/jfd.13090; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fjfd.13090; https://onlinelibrary.wiley.com/doi/pdf/10.1111/jfd.13090; https://onlinelibrary.wiley.com/doi/full-xml/10.1111/jfd.13090

Abstract To identify the pathogens causing saprolegniosis among farmed fish in Nova Scotia, 172 infected tissues and 23 water samples were collected from six species of teleosts: Atlantic salmon ( Salmo salar ), brown trout ( Salmo trutta ), Arctic charr ( Salvelinus alpinus ), brook trout ( Salvelinus fontinalis ), striped bass ( Morone saxatilis ) and rainbow trout ( Oncorhynchus mykiss ) at nine facilities over a 600 km range. Following laboratory culture, 132 isolates were recovered. Six species of oomycetes were identified from analysis of the internal transcribed spacer (ITS) sequence of the nrDNA: Saprolegnia parasitica , Saprolegnia ferax , Saprolegnia diclina , Saprolegnia aenigmatica , Saprolegnia torulosa , Saprolegnia sp. and Pythiopsis cymosa . Further phylogenetic analyses of the ITS and cytochrome c oxidase subunit 1 ( Cox1 ) regions revealed four strains of Saprolegnia parasitica (named here as S1, S2, S3 and S4), of which S1 and S2 were common (37% and 42% of the isolates), and two strains of S. ferax . Among S. parasitica , S2 and S3 are more closely related to each other than to S1 based on the phylogenetic analyses and predicted RNA secondary structure of the ITS region. Sexual structures with a similar morphology were formed by S1 and S3 in vitro , but were not formed by S2.