Morphological and molecular characterization of two species of Saprolegnia isolated from a rainbow trout (Oncorhynchus mykiss) hatchery in Iran

Abstract

In the present study, we aimed to identify Saprolegnia spp. from infected rainbow trout eggs in a hatchery in the north (Mazandaran province) of Iran. Morphological identification was conducted by light microscopic observation of various life stages of Saprolegnia. For the molecular characterization, the internal transcribed spacer (ITS) region was amplified by using universal primers ITS 1 and ITS 4. Based on morphological and molecular findings, two Saprolegniaspp. have been identified. i.e., Saprolegniaparasitica (Isolate KMG3, MW819780) and S. salmonis (Isolates KMG1, MW819740 and KMG2, MW819707). It is worth mentioning that the latter - S. salmonis- is the first report in Iran. The phylogenetic tree inferred by a Neighbor-Joining model revealed that three representative isolates with a well-supported value together with the known isolates of S. parasiticaand S. salmonisformed a well-defined clade. An in vitro experiment was conducted to study the growth of S. salmonis (KMG2) and S. parasitica (KMG3) at various incubation temperatures. Both species showed similar hyphal growth rates at 10 and 18°C after 3 days of incubation (P > 0.05).