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

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