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Diseases of Aquatic Organisms

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DAO 53:47-53 (2003)  -  doi:10.3354/dao053047

Prevalence of a single fish-pathogenic Saprolegnia sp. clone in Finland and Sweden

Eakaphun Bangyeekhun1, Päivi Pylkkö2, Pia Vennerström3, Henry Kuronen4, Lage Cerenius1,*

1Department of Comparative Physiology, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18A, 752 36 Uppsala, Sweden
2Finnish Game and Fisheries Research Institute/Laukaa Aquaculture and Fisheries Research, Vilppulantie 415, 41360 Valkola, Finland
3National Veterinary and Food Research Institute, PO Box 45, 00581 Helsinki, Finland
4National Veterinary and Food Research Institute, Oulu Regional Unit, PO Box 517, 90101 Oulu, Finland
*Corresponding author. Email:

ABSTRACT: Thirty-one isolates of Saprolegnia sp., most originating from infected salmon or trout, were characterised genetically and physiologically. The majority (6 of 31) of the isolates from several widely separated geographical locations was found to be genetically almost identical as assessed by RAPD-PCR. The remaining isolates belonged to 3 different groups with 1 to 3 representatives each. It is suggested that the first group of isolates represents a virulent form of the organism that has been widely spread by clonal propagation. The ability to repeated zoospore emergence, as an alternative to direct germination, seems to characterise specific Saprolegnia genotypes that may have adapted to certain hosts.

KEY WORDS: Saprolegnia · Saprolegniosis · Fish disease · Random amplification of polymorphic DNA RAPD · Repeated zoospore emergence

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