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. 

Keywords

• Fusarium oxysporum f.sp. cepae
• Alternative control
• Salts

Antifungal effect of some salts against Fusarium oxysporum fsp. cepae, the causal agent of Fusarium Basal Rot of Onion

Abstract

This study was performed to evaluate the efficacy of 26 different salts as possible alternatives to synthetic fungicides for the control of Fusarium oxysporum fsp. cepae, the causal agent of Fusarium basal rot. A preliminary evaluation of the salts in vitro tests was performed at 2% (w/v). Among these salts, potassium acetate, potassium chloride, potassium nitrate, potassium phosphate dibasic, sodium chloride, sodium sulfate and trisodium phosphate enhanced the mycelial growth of the fungus compared to that of control (P ≤ 0.05). Except for diammonium phosphate, 15 other salts reduced mycelial growth to some extent (16.61-83.44%) (P ≤ 0.05). Ammonium bicarbonate, ammonium carbonate and sodium metabisulfite completely inhibited mycelial growth, therefore used for further testing in soil. There were no significant differences between the inhibitory effects of ammonium bicarbonate, ammonium carbonate and sodium metabisulfite on the mycelial growth of the fungus (P ≤ 0.05). However, the LD50, minimum inhibition concentration (MIC), and minimum fungicidal concentration (MFC) values found that sodium metabisulfite was more toxic to the fungus compared to two other salts. In soil tests, sodium metabisulfite completely inhibited the fungus at 0.4%. In contrast, ammonium bicarbonate and ammonium carbonate was able to inhibit the fungus at the highest concentration used in the study (P ≤ 0.05).

The present study showed that F. oxysporum f. sp. cepae grow both on acidic and basic pH values. The fungus grown without inhibition between pH 6 and 9, but significantly decreased at higher and lower pH values (P ≤ 0.05). At pH 12, the mycelial growth was completely inhibited.

Keywords

• Fusarium oxysporum fsp. cepae
• alternative control
• salts
• toxicity