The bull's eye rot, caused by Cryptosporiopsis perennans, is the most important postharvest disease of apples in Brazil. The aims of this study were to evaluate a) the use of potassium phosphite salts isolated or in mixture with the fungicide captan for disease control in the field and in vitro; b) the physical/chemical alterations of fruits and, c) the effect of these salts on peroxidase and phenylalanine ammonia-lyase activity in artificially inoculated apples. Potassium phosphites and captan were applied in the 2007/08 season, at Vacaria City, to an orchard of cv. Pink Lady(r), starting at 45 days or 24h prior to harvest. The activity of peroxidase and phenylalanine ammonia-lyase was measured for apple fruits at 24h and 14 days after inoculations with the pathogen. Applications of potassium phosphite + captan reduced by 60% the postharvest loss caused by bull's eye rot, besides decreasing 66% of the inocula produced on apple surface when applied on the day prior to harvest. Potassium phosphite inhibited the in vitro growth of the fungus without affecting peroxidase and phenylalanine ammonia-lyase activity. Potassium phosphites showed eradicating fungicide action and potential to be used in the integrated management of bull's eye rot.
postharvest; phenylalanine ammonia-lyase; peroxidase; Cryptosporiopsis perennans; Malus domestica
