Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/3/2016
Publication Date: 2/3/2017
Citation: Mattheis, J.P., Rudell, D.R., Hanrahan, I. 2017. Impacts of 1-Methylcyclopropene and controlled atmosphere established during conditioning on development of bitter pit in ‘Honeycrisp’ apples. HortScience. 52:132-137. doi:10.21273/HoRTSCI11368-16.
Interpretive Summary: Premium apple fruit in retail markets have a uniform, attractive appearance. The availability of good looking fruit year round belies the challenges growers face to deliver a blemish-free product to customers. Apples are prone to many disorders during cold storage after harvest, and disorder development results in fruit removed from the commercial marketing stream. These losses reduce fruit availability to consumers as well as reduce returns to growers. Preventing these disorders is a challenge to cold storage operators charged with storing fruit for months prior to delivery to retail markets. One of these disorders, known as bitter pit, results in the appearance of brown spots on the peel and corky, dry tissues in the flesh. The process by which bitter pit develops occurs prior to harvest while fruit are on the tree but symptoms do not usually appear until fruit has been harvested and stored. Availability of postharvest technology that limits the ability of apple fruit to ripen is also useful to control many disorders that occur during storage. By manipulating storage temperature, storage room atmosphere and inhibiting the ability of apple fruit to ripen with existing postharvest technologies, scientists at the USDA, ARS Tree Fruit Research Laboratory in Wenatchee, Washington found development of bitter pit in ‘Honeycrisp’ apples can be reduced. Less bitter pit means more fruit can be packed and shipped, a welcome result for demanding consumers and the commercial apple industry.
Technical Abstract: ‘Honeycrisp’ apples are susceptible to develop the physiological disorder bitter pit. This disorder typically develops during storage, but pre-harvest lesion development can also occur. ‘Honeycrisp’ is also chilling sensitive and fruit is typically held at 10-20 oC after harvest for up to 7d to reduce development of chilling injury during subsequent cold storage. This temperature conditioning period followed by a lower storage temperature (2-4 oC) reduces chilling injury risk but can exacerbate bitter pit development. Bitter pit development can be impacted in other apple cultivars by the use of controlled atmosphere (CA) storage and/or 1-methylcyclopropene (1-MCP). Studies were conducted to evaluate efficacy of CA and/or 1-MCP to manage ‘Honeycrisp’ bitter pit development. Apples from multiple lots, obtained at commercial harvest, were initially held at 10 oC and exposed to 0 or 1 µl L-1 1-MCP the day of receipt. CA (3kPa O2, 0.5kPa CO2) was established after an additional 1d or 9d, then O2 was reduced to 2kPa 2d after CA establishment. 1-MCP and CA both reduced bitter pit development compared with untreated fruit stored in air, and bitter pit incidence was lowest for apples exposed to 1-MCP the day after harvest with CA established during conditioning. Development of diffuse flesh browning and cavities, reported to occur during ‘Honeycrisp’ CA storage, was observed in some lots. Incidence of these disorders was not enhanced by establishing CA 2d compared with 9d after harvest. 1-MCP and CA slowed peel color change, loss of soluble solids concentration (SSC) and titratable acidity (TA), and reduced ethylene production and respiration rate. The results indicate potential for the postharvest management of bitter pit development in ‘Honeycrisp’ apple through use of 1-MCP and/or CA storage.