A multidisciplinary approach reveals new aspects of superficial scald aetiology and cold resistance mechanism in ‘Granny Smith’ apples

Chilling injuries represent a major issue in postharvest management of apple fruit. The usage of low temperature to extend the storage capacity can lead to the development of many physiological disorders, such as superficial scald, which seriously affect the entire marketability. The main symptom of superficial scald is represented by a diffuse browning coloration, generally limited to the skin and the underlying six-cell layer, generally occurring after the re-establishment of room temperature conditions. In this work, RNA-seq technology was employed to characterize the transcription dynamics of ‘Granny Smith’ apples affected by superficial scald and treated with 1-methylcyclopropene (1-MCP), an ethylene competitor known to control this physiopathy. In addition, a metabolomic profiling was also performed to determinate correspondences between gene expressions and phenotypic traits (polyphenol accumulations and production of volatiles mainly). With the aim to step forward in our understanding about the aetiological cause of superficial scald, particular effort was dedicated to decipher the effect of 1-MCP on the fruit transcriptomic pattern.