Aims: To investigate antifungal effects of two antagonistic yeasts on postharvest sour rot caused by Geotrichum citri‐aurantii in citrus and evaluate possible mechanisms.
Methods and Results: Cell suspension of Cryptococcus laurentii at 108 to 109 cells per ml effectively reduced sour rot incidence from 55·6% among untreated control fruit to 29·9–20·7% after 5 days of incubation at 26°C. Application of cell‐free culture filtrate of C. laurentii was effective in reducing the sour rot, but the effectiveness was lower than that of the cell suspension (1 × 108 cells per ml). In addition, C. laurentii multiplied more rapidly than Rhodosporidium paludigenum at 26°C. The fruit inoculated with the two yeasts demonstrated changes in peroxidase and superoxide dismutase activity. Cryptococcus laurentii, in particular, was capable of inducing a striking response in treated citrus fruits.
Conclusions: The antifungal ability of C. laurentii can be attributed to the competitions of nutrients and space, defensive responses and possible secretion of antibiotic compounds.
Significance and Impact of the Study: The use of such antagonists may constitute an important alternative to synthetic fungicides for controlling postharvest sour rot in citrus.
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