The incidence of Neofabraea spp. in 'Pinova' apples can be reduced at elevated storage temperatures

The apple cultivar 'Pinova' is highly susceptible to fungal storage rots, mainly caused by Neofabraea alba and N. perennans (syn. Gloeosporium album and G. perennans). Experiments over five years evaluated the effect of different storage temperatures in combination with modern storage technologies on the incidence of fungal rots in 'Pinova' apples. Studies were carried out in three identical controlled atmosphere (CA) storage rooms (each 11 t capacity) at the Competence Centre for Fruit Growing at Lake Constance (KOB). Treatments compared ultra-low oxygen (ULO) conditions (1.0 kPa O-2 + 2.5 kPa CO2) at 1 degrees C with ULO at 3 to 5 degrees C in combination with 1-methylcyclopropene (1-MCP) or with dynamic controlled atmosphere (DCA; similar to 0.5 kPa O-2 + 2.5 kPa CO2), controlled by chlorophyll fluorescence, at 1 and 3 degrees C. After 7 to 8 months storage, similar to 1200 kg of fruit (4x orchard bins) per treatment were classified as either rotten or healthy on an electronic fruit grader equipped with manual touch sensors. Results show a sizable reduction in fungal rots when fruit were stored under higher temperatures (3 to 5 degrees C) compared to storage at 1 degrees C regardless of the storage conditions (ULO, ULO + 1-MCP or DCA). Increased storage temperatures had no negative effects on the quality parameter fruit firmness (FF). 'Pinova' is a slow softening cultivar and FF at the recommended storage temperature of 1 degrees C did not differ from fruit stored at 3, 4 or 5 degrees C. In conclusion, increased storage temperatures might be an effective way to reduce the incidence of Neofabraea spp. storage rots while still maintaining fruit quality. Additionally, increased storage temperatures can provide a substantial reduction in energy consumption during storage, as experiments over multiple years have shown.