2017 ASHS Annual Conference

Malus domestica Borkh cv Honeycrisp is susceptible to bitter pit (BP) which is a calcium-related physiological disorder in the fruit. BP symptoms include internal and external brown, dry lesions on the fruit. The disorder typically develops during storage, but it can also develop preharvest. ‘Honeycrisp’ is also a chilling sensitive variety, and fruit is typically held at 10-20 °C after harvest for up to 7 days to reduce development of chilling injury (CI) during subsequent cold storage. The temperature conditioning period followed by a lower storage temperature (2-4 °C) reduces CI risk but can increase BP development. The utilization of controlled atmosphere (CA) storage and an ethylene antagonist, 1-methylocyclopropene (1-MCP), are common practices used to slow down fruit respiration and to extend the storage life of apples. The objective of this research was to evaluate how 1-MCP and CA establishment during temperature conditioning impacts the development of BP in ‘Honeycrisp’ apples. Fruit from one commercial ‘Honeycrisp’/Bud 9 orchard in Quincy, Washington was obtained and held at 10 °C for 7 days and then cooled to 3 °C. Half the fruit was treated with 42 µmol·L^-1 1-MCP the day of receipt while held at 10 °C. Fruit were stored in air or CA (2.5 kPa O₂, 0.5 kPa CO₂) established 1 day after receipt at 10 °C, and fruit remained in CA for 1, 2, 3 or 4 weeks followed by storage in air up to 4 months. The final storage temperature was 3 °C. At harvest, maturity analyses (starch index, firmness, soluble solids content, titratable acidity, weight, color, internal ethylene content, dry matter) were performed. BP incidence was reduced by 20% when exposed to 1-4 weeks in CA followed by storage in air compared with fruit stored only in air, irrespective of whether fruit was treated or not with 1-MCP. When 1-MCP-treated fruit was held in CA during conditioning, BP was 12 % less compared with fruit treated with 1-MCP and stored in air. Fruit stored in CA without 1-MCP had 27 % less BP compared with untreated fruit stored in air. 1-MCP slowed loss of soluble solids content (SSC), titratable acidity and had lower internal ethylene concentrations. Bitter pit incidence typically developed within 1 month of harvest and changed little after 2 months. Results suggests that 1-MCP and/or CA established during conditioning period could be used for BP control in ‘Honeycrisp’ apples during postharvest storage.