EFFECT OF ORGANIC AND INORGANIC SALTS AS ALTERNATIVE STRATEGY FOR THE CONTROL OF POSTHARVEST CITRUS SOUR ROT AGENT GEOTRICHUM CANDIDUM

Abstract

To find an alternative to the fungicide treatment with guazatine currently used to control postharvest citrus sour rot caused by Geotrichum candidum, we screened 32 salt compounds presently used as food additives for their activity against this fungus. The lowest Minimum Inhibitory Concentration (MIC) values were obtained with ammonium carbonate and EDTA (0.1% w/v), followed by boric acid, sodium carbonate and sodium metabisulfite (0.25% w/v). The mycelial growth was not affected by medium pH values in the range of 4.0 to 12.0. The most inhibiting salt compounds were then tested for their ability to reduce the arthrospore germination in vitro and sour rot incidence in vivo. The arthrospore germination was completely inhibited by 75 mM EDTA, boric acid, sodium metabisulfite, sodium carbonate, sodium sulfate and sodium thiosulfate. Incidence of sour rot was reduced to 25.93% when mandarin fruits where treated with 3% sodium salicylate or boric acid, and to 38.89% when they were treated with 3% EDTA, compared with 100% rotten fruits of the untreated control. These results suggest that sodium salicylate, boric acid and EDTA may be useful compounds to control citrus sour rot, thus being a sustainable alternative to the use of guazatine mainly in organic production.