Effect of sulfite–hydrosulfite and nitrite on thiol redox state, oxidative stress and sclerotial differentiation of filamentous phytopathogenic fungi

This study shows that Na2S2O4, Na2SO3 and NaNO2 decreased differentiation of filamentous phytopathogenic fungi representing the four main types of sclerotia at maximum growth non-inhibiting concentrations, and also increased and decreased the oxidized and the reduced components of their thiol redox state, respectively. Na2S2O4, Na2SO3 and NaNO2 also severely inhibited fungal growth at certain concentrations. These effects concurred by the increase of the high oxidative stress indicator lipid peroxidation and could be attributed to the oxidative cytotoxicity of sulfites and nitrite. The cytotoxic mechanism of the latter may be related to the acidic pH. Sulfites and nitrite can be used as potent fungicides against sclerotiogenic phytopathogenic fungi by acting as growth inhibiting cytotoxic oxidants and by sustaining fungi in their undifferentiated hyphal stage, in which they are more vulnerable to degradation by soil microorganisms.