The spreading and molecular characterization of the fungus Saprolegnia parasitica in the water of Al-Diwaniyah river of Iraq

The water mold Saprolegnia parasitica is a chief species of oomycetes that affects a wide range of plant, natural ecosystems, fish and the aquaculture industry. The current study aimed to investigate the isolation and identification of some aquatic fungi like Saprolegnia spp. and also molecular characterization of Saprolegnia parasitica in the water of Al-Diwaniyah river of Iraq using the baiting method for isolation and PCR polymerase chain reaction for molecular diagnosis of fungi. A total of 60 samples were taken from three study sites of river: 25 samples of Al-Shafi’iah city bridge (Najaf road) as first site (S1); 25 samples of Hawly Al-Jamiah road bridge, Umm Al-Khail area, as second site (S2); and 10 samples of Al-Orouba bridge as the third site (S3). Molecular diagnosis was carried out by PCR examination using primers for the rDNA gene and its presence in Saprolegnia parasitica, as DNA was obtained at a concentration of 685.4-99.4 μg/μl and a purity of 1.92-1.8. The samples from the first site gave the highest number of 18 isolates (45%), followed by samples from the second site with 14 isolates (35%). The samples from the third site showed a number of 10 isolates (20%). The species S. parasitica was more visible during February 2020 with a number of 17 isolates, and less visible in April 2021, with a number of 3 isolates. In conclusion, the variation in the presence of the types of infectious aquatic fungi Saprolegnia spp. in the Al-Diwaniyah river of Iraq in different sites and months of 2021 showed a high percentage of isolates for Al-Shafi’iah city bridge (Najaf road) site and the highest number of Saprolegnia parasitica in February 2020. There is a need for further examination of oomycetes in different sites of rivers of Iraq in different months.