Postharvest biological control of grey mold and blue mold on apple by Cryptococcus albidus (Saito) Skinner

The yeast Cryptococcus albidus (Saito) Skinner, an antagonist isolated from peach fruit, was evaluated for biological control capability in 'Fuji' apple after challenge with 1 × 10⁵ or 5 × 10⁴ spores/ml of the postharvest pathogens Botrytis cinerea and Penicillium expansum. The yeast at 1 × 10⁸ CFU/ml of washed cells suspension totally inhibited decay in apple fruits at 23 and 1°C. The concentrations of antagonist and pathogen spores had significant effects on biocontrol effectiveness. Culture filtrate of the yeast failed to provide protection against the two pathogens. The antagonist was compatible with iprodione and calcium chloride. The yeast at 1 × 10⁶ CFU/ml mixed with iprodione at 50 ppm a.i. provided better control of decay than the single application. Calcium chloride facilitated control of B. cinerea and P. expansum by C. albidus at a concentration as low as 10⁵ CFU/ml. Rapid colonisation of apples from wounds was observed by the first 48 h at both 23 and 1°C. This stabilised at the same density thereafter at 23°C, but was lower at 1°C. Efficacy of C. albidus against B. cinerea and P. expansum was maintained when it was applied before the pathogens, but was reduced when applied simultaneously with or after the spores.