1a. Objectives (from AD-416):
1. Characterize differences in orchards that produce fruit with a history of disorder resistance or susceptibility. 2. Determine utility of ethylene green life, fruit density, titratable acidity, chlorophyll fluorescence and chlorophyll absorbance as additional indicators of storability. 3. Identify alternatives to the 7 day 50 oF pre-conditioning protocol. 4. Identify factors contributing to CO2 injury occurring during the initial 30 days after harvest. 5. Identify CA protocols that maximize quality retention and minimize disorders.
1b. Approach (from AD-416):
1. Postharvest chilling sensitivity is orchard specific. Site-specific information (location, elevation, aspect, tree age, rootstock, chemical use) will be obtained for 4-5 orchards with and without history of postharvest chilling disorders. 2. Fruit ethylene production, density, titratable acidity, chlorophyll fluorescence/absorbance are useful indicators of Honeycrisp apple maturity and storability. Fruit from 4-5 orchards harvested on multiple dates prior to and after typical commercial maturity will be analyzed the day of harvest for density, titratable acidity, chlorophyll fluorescence and absorbance. Ethylene production by other fruit from the same harvest will be determined daily for up to 14 days after harvest. Additional fruit from each orchard/harvest will be stored in air or a controlled atmosphere for 3-9 months and fruit quality assessed after removal from storage. 3. ‘Honeycrisp’ chilling injury can be averted by methods other than holding at 7 days at 10 oC prior to cold storage. Fruit held at 10 oC for 0, 1, or 2 days will be cooled to 2 oC stepwise over various periods compare to rapid cooling, held for 3 months, then evaluated for disorders. Diffusive resistance will be assessed for fruit from 4-5 orchards at harvest, fruit will be cooled to 0.5 oC, held 3 months then assessed for disorders. 4. Initial events leading to Honeycrisp CO2 injury occur during the first month after harvest. Fruit will be exposed to 0-4% CO2 plus 0 or 1 ppm 1-MCP in air at 10 oC during 24-72h after harvest, stored at 36 oC for 3 months then assessed for CO2 injury. Other fruit will be treated with diphenylamine then stored at 36 oC in 1,3or5% CO2 with 2% O2 for 3 or 6 months, then evaluated for disorders. 5. Use of controlled atmosphere (CA) storage can slow ripening and reduce disorder incidence of ‘Honeycrisp’ apples. CAs with 1-2% O2 with 1-2% CO2 will be imposed 0, 2, 7 days after harvest with fruit held at 0.5 or 10oC for 7 days then reduced to 2 oC over 3 days.
3. Progress Report:
This project relates to objective 2 of the associated in-house project which seeks to identify factors that influence postharvest fruit quality and development of market limiting physiological disorders. Research plan development for initial project experiments to be conducted in fall 2013 is in progress. Experiments to assess fruit green life, physiological responses to chilling and low O2 controlled atmosphere storage will be conducted.