Genetic analysis of oomycete isolates from trout ponds

Oomiceti su patogeni mikroorganizmi koji uzrokuju bolesti koje uzrokuju milijunske gubitke u akvakulturi i agrokulturi. Budući su zastupljenost i biologija oomiceta u ribogojilištima Hrvatske uglavnom nepoznati, cilj ovog diplomskog rada bio je identificirati prisutne vrste oomiceta, izoliranih kao čista kultura iz uzoraka prikupljenih na ribogojilištu Belski dol, te ustanoviti njihove filogenetske odnose na temelju genetske analize ITS-regije 5,8S rRNA gena. Filogenetski odnosi rekonstruirani su pomoću metode Bayesianovog zaključivanja (BA, eng. Bayesian analysis) pomoću programa Mr. Bayes sa 100 000 iteracija. Molekularno-filogenetička analiza ustanovila je da od ukupno 48 izolata uzgojenih kao čiste kulture; dvadeset i pet pripadaju Pythium sp., četrnaest vrsti Saprolegnia parasitica, pet izolata identificirano je kao Saprolegnia ferax, tri izolata spadaju u Leptolegnia sp., dok samo jedan izolat spada u Saprolegnia australis. Upotreba PCR testova za detekciju patogenih oomiceta omogućila bi rano oktrivanje prisutnosti patogena i predviđanje “vrućih točaka” s povećanim rizikom izbijanja bolesti. Time bi se utjecalo na smanjenje ekonomskih gubitaka i potaknulo na poboljšanje uvjeta uzgoja.Oomycetes are pathogenic microorganisms that cause diseases which can lead to millions of losses in aquaculture and agroculture. Considering that existing pathogen identification methods are based on the cultivation of isolates in growth-medium, a procedure that is time-consuming and often unsuccessful, the aim of this study was to identify the species of oomycetes isolated as pure cultures from samples collected at fish farm “Belski dol” and also to identify their phylogenetic relationship based on genetic analysis of the ITS region of the 5.8S rRNA gene. Phylogenetic relationship was reconstructed using the Bayesian analysis (BA) method using Mr. Bayes with 100,000 iterations. Molecular-phylogenetic analysis found twenty-five Phytium sp., fourteen Saprolegnia parasitica, five Saprolegnia ferax, three isolates belong to Leptolegnia sp., while only one belongs to Saprolegnia australis. The use of PCR assays for detection of pathogenic oomycetes would allow the early detection of pathogens and the prediction of “hot sports” with increased risk of disease outbreaks. This would have the effect of reducing economic losses and stimulating the improvement of farming conditions