Abstract
Oomycete pathogens in freshwaters, such as Saprolegnia parasitica and Aphanomyces astaci, are responsible for fish/crayfish population declines in the wild and disease outbreaks in aquaculture. Although the formation of infectious zoospores in the laboratory can be triggered by washing their mycelium with natural water samples, the physico-chemical properties of the water that might promote sporulation are still unexplored. We washed the mycelia of A. astaci and S. parasitica with a range of natural water samples and observed differences in sporulation efficiency. The results of Partial Least Squares Regression (PLS-R) multivariate analysis showed that SAC (spectral absorption coefficient measured at 254 nm), DOC (dissolved organic carbon), ammonium-N and fluoride had the strongest positive effect on sporulation of S. parasitica, while sporulation of A. astaci was not significantly correlated with any of the analyzed parameters. In agreement with this, the addition of environmentally relevant concentrations of humic acid, an important contributor to SAC and DOC, to the water induced sporulation of S. parasitica but not of A. astaci. Overall, our results point to the differences in ecological requirements of these pathogens, but also present a starting point for optimizing laboratory protocols for the induction of sporulation.
Highlights
Animal pathogenic oomycetes are a cause of serious diseases worldwide [1–3], and in freshwater ecosystems species from the genera Aphanomyces and Saprolegnia are the most significant, since they cause severe disease outbreaks both in aquaculture and in the wild [4–7]
We hypothesized that physico-chemical characteristics of natural waters can affect the intensity of sporulation of freshwater pathogenic oomycetes, and the aim of this study was to test for the first time the sporulation efficiency of two oomycete pathogens, A. astaci and
Using Partial Least Squares Regression (PLS-R) multivariate analysis we examined the relationship between the sporulation intensity of A. astaci and S. parasitica and the physico-chemical parameters of water
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Animal pathogenic oomycetes are a cause of serious diseases worldwide [1–3], and in freshwater ecosystems species from the genera Aphanomyces and Saprolegnia are the most significant, since they cause severe disease outbreaks both in aquaculture and in the wild [4–7]. A disease caused by Aphanomyces astaci is responsible for decimating the populations of indigenous crayfish species in Europe [8] and elsewhere (e.g., Asia and South America) [9–12]. The pathogen was introduced into Europe along with North
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