Abstract:
Integrated recirculated systems combining aquaculture and hydroponic, known as aquaponic systems, are today more and more studied. However one critical management point is still unclear, namely plant pest management. In aquaponics, diseases found in the system are commonly the same than in hydroponics. Root pathogens and more specially oomycetes fungi responsible of root rot are among the most problematic due to their capacity of dispersion linked to zoospores production. On the other hand, compared with hydroponics, aquaponic plants production can give similar yields with less mineral nutrients concentration and even better yields for equivalent concentration in the nutritive solution (Pantanella et al. 2010; Delaide et al. 2016; Saha et al. 2016; Suhl et al. 2016). Furthermore one article opens the hypothesis of an in vitro protective activity of fish effluents versus plant pathogens (Gravel et al., 2015). Both phenomena could be linked to microorganisms or compounds present in fish water. Assumptions that don't seem aberrant in light of suppressive action already observed in hydroponic systems (Postma et al., 2008). In addition, microorganisms potentially involving in this action could be richer because of organic compounds in aquaponic water. To confirm these observations, in vitro and in vivo experimentations have been made on the ability of recirculating aquaculture water to procure a plant protection effect towards Pythium aphanidermatum (Edson) Fitzp, an oomycetes pathogen. Firsts in vitro results show a significant decrease of mycelium production when 25% of fish water is present in a V8 CaCO3 broth. But no difference was made between the control and the broth containing 25% of 0,2 µm filtrated fish water. These finding highlight a direct microbial antagonist activity of recirculating aquaculture water against P. aphanidermatum. However dissolved compounds don't display a direct action on this pathogen but biostimulation or elicitation effect on plants can't be excluded.
Key words: aquaponics, aquaculture, suppressive microflora, biocontrol, plant protection, microbiota, lettuce, root disease, Pythium aphanidermatum
References
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