On-Tree water spray affects superficial scald severity and fruit quality in ‘Granny Smith’ apples

Abstract: ‘Granny Smith’, a variety of apple is susceptible to superficial scald. Superficial scald is one of the most controversial post-harvest physiological disorders. At the moment there is no complete documented information about the pre-harvest factors responsible for its induction, symptom development and control methods. Accordingly, this study was to examine the possible link between the disorder and qualitative indicators of environmental changes, particularly humidity during early fruit growth and cell division. The study was conducted in a commercial orchard in Abyek region, Alborz-Iran in 2014. Examined trees were 7 year-olds and grafted onto seedling rootstocks. On-tree water spray was done during full bloom, 17 May till 6 June, in four levels including 0-day, 7-day, 14-day, and 21-day water spray. Fruits were harvested 160 days after full bloom (DAFB) and stored in a commercial chamber (5±2?C) in four levels including: 0-day (before storage), 30-day, 60-day and 90-day of cold storage. Superficial scald severity in the 0-day water spray samples was 91.7 % after 60- and 90-day storage, while all three water spray treatment regime significantly reduced it after 60- and 90-day storage. The 14-day water spray was significantly more effective in reducing the incidence of superficial scald which was 91 % after 60-day and 75 % after 90-day storage. The highest firmness (9.5 kg cm^-2) was observed before storage. The highest SSC was observed in the 7-day water spray and before the storage. Interestingly, on-tree water spray considerably decreased superficial scald and/or delayed its severity during mid- and long-term storage.