Evaluation of Antifungal Activity of Sodium Salts against Onion Basal Rot Caused by Fusarium oxysporum f.sp cepae

The efficacy of twelve sodium salts as possible alternatives to synthetic fungicides for the control of onion basal rot caused by Fusarium oxysporum f.sp. cepae was evaluated. In vitro tests showed that there were significant differences between the inhibitory effects of sodium salts on the mycelial growth (P <= 0.05) and 2% (w/v) concentrations of sodium metabisulfite and sodium fluoride completely inhibited mycelial growth of the fungus, while other salts did not. Sodium metabisulfite and sodium phosphate monobasic had lower pH values than the other salts. Unlike sodium metabisulfite, sodium phosphate monobasic could not decrease the mycelial growth. The ED50, minimum inhibition concentration (MIC), and minimum fungicidal concentration (MFC) values indicated that sodium metabisulfite was more inhibitory to the fungus compared to sodium fluoride. In soil tests, inhibitory effect of sodium metabisulfite on the fungus was higher than that of sodium fluoride, where sodium metabisulfite completely inhibited mycelial growth at even 0.4% concentration.