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Boric acid inhibits germination and colonization of Saprolegnia spores in vitro and in vivo.

Ali SE, Thoen E, Evensen Ø, Skaar I - PLoS ONE (2014)

Bottom Line: The banning of malachite green increased the demand for finding effective alternative treatments to control the disease.Under in vitro conditions, boric acid was able to decrease Saprolegnia spore activity and mycelial growth in all tested concentrations above 0.2 g/L, while complete inhibition of germination and growth was observed at a concentration of 0.8 g/L.During the experiments no negative impact with regard to hatchability and viability was observed in either eggs or fry, which indicate safety of use at all tested concentrations.

View Article: PubMed Central - PubMed

Affiliation: Norwegian Veterinary Institute, Oslo, Norway.

ABSTRACT
Saprolegnia infections cause severe economic losses among freshwater fish and their eggs. The banning of malachite green increased the demand for finding effective alternative treatments to control the disease. In the present study, we investigated the ability of boric acid to control saprolegniosis in salmon eggs and yolk sac fry. Under in vitro conditions, boric acid was able to decrease Saprolegnia spore activity and mycelial growth in all tested concentrations above 0.2 g/L, while complete inhibition of germination and growth was observed at a concentration of 0.8 g/L. In in vivo experiments using Atlantic salmon eyed eggs, saprolegniosis was controlled by boric acid at concentrations ranging from 0.2-1.4 g/L during continuous exposure, and at 1.0-4.0 g/L during intermittent exposure. The same effect was observed on salmon yolk sac fry exposed continuously to 0.5 g/L boric acid during the natural outbreak of saprolegniosis. During the experiments no negative impact with regard to hatchability and viability was observed in either eggs or fry, which indicate safety of use at all tested concentrations. The high hatchability and survival rates recorded following the in vivo testing suggest that boric acid is a candidate for prophylaxis and control of saprolegniosis.

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In vitro effect of boric acid on the germination and colonization of Saprolegnia spores.Effect of boric acid on the germination and colonization of Saprolegnia spores following 48 hours incubation. (a1 and a2) Grade 3: Profuse Saprolegnia hyphal growth on sesame seeds in the non- treated control group (water). (b1 and b2) Grade 3: germinating spores with mycelial growth on the sesame seeds (boric acid <0.2 g/L). (c1 and c2) Grade 2: reduced germination rate and minimal mycelial growth on the sesame seeds (boric acid 0.2–0.4 g/L). (d1 and d2) Grade 1: germinating spores without growing mycelia on the sesame seeds (boric acid 0.5–0.7 g/L). (e1 and e2) Grade 0: no germinating spores, no growing mycelia on the sesame seeds (boric acid ≥0.8 g/L). (f1 and f2) Grade 0: positive control group (bronopol), no spore germination with absence of the growing mycelia on sesame seeds.
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pone-0091878-g001: In vitro effect of boric acid on the germination and colonization of Saprolegnia spores.Effect of boric acid on the germination and colonization of Saprolegnia spores following 48 hours incubation. (a1 and a2) Grade 3: Profuse Saprolegnia hyphal growth on sesame seeds in the non- treated control group (water). (b1 and b2) Grade 3: germinating spores with mycelial growth on the sesame seeds (boric acid <0.2 g/L). (c1 and c2) Grade 2: reduced germination rate and minimal mycelial growth on the sesame seeds (boric acid 0.2–0.4 g/L). (d1 and d2) Grade 1: germinating spores without growing mycelia on the sesame seeds (boric acid 0.5–0.7 g/L). (e1 and e2) Grade 0: no germinating spores, no growing mycelia on the sesame seeds (boric acid ≥0.8 g/L). (f1 and f2) Grade 0: positive control group (bronopol), no spore germination with absence of the growing mycelia on sesame seeds.

Mentions: Boric acid inhibits germination and colonization of Saprolegnia spores in vitro and has a static effect on mycelium growth. Our first approach was to test the ability of boric acid to influence germination and colonization of Saprolegnia spores in vitro. Saprolegnia spores germinated and colonized sesame seeds in all groups at BA concentrations below 0.2 g/L, however, the growth rate was slow compared to the non-treated control even at this low concentration. When BA concentrations of 0.8 g/L and above were used, inoculated Saprolegnia spores did not germinate (Table 1 & Fig. 1 and 2). We also tested the effect on mycelial growth and at concentrations above 0.6 g/L, BA arrests mycelia and no further growth is seen (Table 2 & Fig. 3).


Boric acid inhibits germination and colonization of Saprolegnia spores in vitro and in vivo.

Ali SE, Thoen E, Evensen Ø, Skaar I - PLoS ONE (2014)

In vitro effect of boric acid on the germination and colonization of Saprolegnia spores.Effect of boric acid on the germination and colonization of Saprolegnia spores following 48 hours incubation. (a1 and a2) Grade 3: Profuse Saprolegnia hyphal growth on sesame seeds in the non- treated control group (water). (b1 and b2) Grade 3: germinating spores with mycelial growth on the sesame seeds (boric acid <0.2 g/L). (c1 and c2) Grade 2: reduced germination rate and minimal mycelial growth on the sesame seeds (boric acid 0.2–0.4 g/L). (d1 and d2) Grade 1: germinating spores without growing mycelia on the sesame seeds (boric acid 0.5–0.7 g/L). (e1 and e2) Grade 0: no germinating spores, no growing mycelia on the sesame seeds (boric acid ≥0.8 g/L). (f1 and f2) Grade 0: positive control group (bronopol), no spore germination with absence of the growing mycelia on sesame seeds.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC3974685&req=5

pone-0091878-g001: In vitro effect of boric acid on the germination and colonization of Saprolegnia spores.Effect of boric acid on the germination and colonization of Saprolegnia spores following 48 hours incubation. (a1 and a2) Grade 3: Profuse Saprolegnia hyphal growth on sesame seeds in the non- treated control group (water). (b1 and b2) Grade 3: germinating spores with mycelial growth on the sesame seeds (boric acid <0.2 g/L). (c1 and c2) Grade 2: reduced germination rate and minimal mycelial growth on the sesame seeds (boric acid 0.2–0.4 g/L). (d1 and d2) Grade 1: germinating spores without growing mycelia on the sesame seeds (boric acid 0.5–0.7 g/L). (e1 and e2) Grade 0: no germinating spores, no growing mycelia on the sesame seeds (boric acid ≥0.8 g/L). (f1 and f2) Grade 0: positive control group (bronopol), no spore germination with absence of the growing mycelia on sesame seeds.
Mentions: Boric acid inhibits germination and colonization of Saprolegnia spores in vitro and has a static effect on mycelium growth. Our first approach was to test the ability of boric acid to influence germination and colonization of Saprolegnia spores in vitro. Saprolegnia spores germinated and colonized sesame seeds in all groups at BA concentrations below 0.2 g/L, however, the growth rate was slow compared to the non-treated control even at this low concentration. When BA concentrations of 0.8 g/L and above were used, inoculated Saprolegnia spores did not germinate (Table 1 & Fig. 1 and 2). We also tested the effect on mycelial growth and at concentrations above 0.6 g/L, BA arrests mycelia and no further growth is seen (Table 2 & Fig. 3).

Bottom Line: The banning of malachite green increased the demand for finding effective alternative treatments to control the disease.Under in vitro conditions, boric acid was able to decrease Saprolegnia spore activity and mycelial growth in all tested concentrations above 0.2 g/L, while complete inhibition of germination and growth was observed at a concentration of 0.8 g/L.During the experiments no negative impact with regard to hatchability and viability was observed in either eggs or fry, which indicate safety of use at all tested concentrations.

View Article: PubMed Central - PubMed

Affiliation: Norwegian Veterinary Institute, Oslo, Norway.

ABSTRACT
Saprolegnia infections cause severe economic losses among freshwater fish and their eggs. The banning of malachite green increased the demand for finding effective alternative treatments to control the disease. In the present study, we investigated the ability of boric acid to control saprolegniosis in salmon eggs and yolk sac fry. Under in vitro conditions, boric acid was able to decrease Saprolegnia spore activity and mycelial growth in all tested concentrations above 0.2 g/L, while complete inhibition of germination and growth was observed at a concentration of 0.8 g/L. In in vivo experiments using Atlantic salmon eyed eggs, saprolegniosis was controlled by boric acid at concentrations ranging from 0.2-1.4 g/L during continuous exposure, and at 1.0-4.0 g/L during intermittent exposure. The same effect was observed on salmon yolk sac fry exposed continuously to 0.5 g/L boric acid during the natural outbreak of saprolegniosis. During the experiments no negative impact with regard to hatchability and viability was observed in either eggs or fry, which indicate safety of use at all tested concentrations. The high hatchability and survival rates recorded following the in vivo testing suggest that boric acid is a candidate for prophylaxis and control of saprolegniosis.

Show MeSH
Related in: MedlinePlus