Impact of storage technologies on epiphytic blemishes of apple fruit

Epiphytic fungi that cause symptoms such as sooty blotch, white haze or flyspeck provoke relevant blemishes especially on organic apples in South Tyrol (North Italy). By microbiological isolation as well as by cloning and sequencing of the microbial community present on the epidermis of the apple, it has been possible to identify so far more than 30 fungal species. The most frequently detected genera include Aureobasidium, Phoma, Fusarium and Cladosporium. Satisfactory protection against this fungal complex has often not been possible in orchards because of the limited availability of fungicides, and incidence increases due to significant restrictions in the application of active substances, the enhanced occurrence of honeydew-secreting insects and agronomic practices such as foliar nutrition or hail nets. Moreover, the fungal complex may also proliferate during storage. Therefore, the influence of different storage technologies to prevent epiphyte development after harvest was studied: the modification of air atmosphere during storage in ultra-low oxygen (CA-ULO), differences in humidity, ionization of the atmosphere, ozone enrichment of the atmosphere at different intervals and concentration. The time of harvest, or respective ripening stage, was taken into account. The degree of humidity modulated the occurrence of symptoms and indicated the importance of the coordinated management of the storage cold rooms. Fruit quality could be influenced by this. Ionization and ozone enrichment showed an increasing influence on the development of epiphytes with different expressions of symptoms. Greasiness of cuticle has been observed as a side effect, the causes of which need to be investigated in more detail in order not to be an obstacle to commercialization. In addition, there are still numerous questions to be clarified for the implementation of the experimental results on practical scale.