Antifungal Effect of Various Salts Against Fusarium oxysporum f.sp cepae, the Causal Agent of Fusarium Basal Rot of Onion

Abstract

This study evaluated the efficacy of 26 different salts as possible alternatives to synthetic fungicides for the control of Fusarium oxysporum f.sp. cepae, the causal agent of Fusarium basal rot. Preliminary evaluation of salt tests was performed in vitro using 2% concentration (w/v). When compared to control, potassium acetate, potassium chloride, potassium nitrate, potassium phosphate dibasic, sodium chloride, sodium sulfate and trisodium phosphate significantly enhanced the mycelial growth of the fungus; diammonium phosphate had no significant effect; 15 other salts reduced mycelial growth to some extent (16.61-83.44%) (P <= 0.05); and ammonium bicarbonate, ammonium carbonate and sodium metabisulfite completely inhibited mycelial growth. No significant difference in the inhibitory effects of ammonium bicarbonate, ammonium carbonate and sodium metabisulfite was observed in vitro (P <= 0.05); however, the ED50, minimum inhibition concentration (MIC), and minimum fungicidal concentration (MFC) values indicated sodium metabisulfite to be more toxic to F. oxysporum f.sp. cepae than ammonium carbonate and ammonium bicarbonate. Soil tests showed that 0.4% sodium metabisulfite completely inhibited fungal growth, whereas only the highest concentrations of ammonium bicarbonate and ammonium carbonate tested (2%) were able to inhibit growth (P <= 0.05). The present study also showed that F. oxysporum f.sp. cepae capable of growth in both acidic and basic environments. While the fungus showed uninhibited growth at pH values between 6-9, growth decreased significantly at both higher and lower pH values (P <= 0.05) and was completely inhibited at pH 12.