ARS | Publication request: Establishing a diagnostic metabolic profile for soggy breakdown, a physiological disorder of stored ‘Honeycrisp’ apple fruit

Submitted to: Metabolomics
Publication Type: Abstract Only
Publication Acceptance Date: June 25, 2012
Publication Date: June 25, 2012
Citation: Leisso, R.S., Hanrahan, I., Buchanan, D.A., Lee, J., Mattheis, J.P., Rudell Jr, D.R. 2012. Establishing a diagnostic metabolic profile for soggy breakdown, a physiological disorder of stored ‘Honeycrisp’ apple fruit. Metabolomics.

Technical Abstract: ‘Honeycrisp’ is an economically important apple cultivar in the United States, increasing rapidly in planted acreage in all major apple growing regions. Long-term cold storage can enhance value by enabling a longer window of availability, but the physiological disorder known as soggy breakdown can severely impact the quality of stored fruit, rendering the product unmarketable. Soggy breakdown is a chilling injury characterized by sharply demarcated ribbons of dark brown tissue in the fruit cortex. The disorder often appears within several weeks of cold storage, but incidence is highly variable among orchards. As with other physiological disorders of apple fruit, soggy breakdown ostensibly has a latent pathology, where the event provoking the disorder occurs early in storage, several weeks before symptoms appear. Diagnostic protocols are lacking beyond visual symptom assessment. A step towards creating forensic tools that distinguish this browning disorder from similar disorders is constructing a metabolic fingerprint specific to this disorder. The study establishes a diagnostic metabolic profile for soggy breakdown. GC and HPLC-MS were used to assess the untargeted metabolic profile of fruit obtained from three orchards of differing growing environments in Washington State and subjected to cold storage from four to twelve weeks. Levels of a broad range of volatile or non-volatile polar and non-polar metabolites were evaluated using mass spectral libraries made specifically for apple fruit. Identified compounds include both primary and secondary metabolites important to fruit quality that comprise flesh color and flavor as well as cellular function and integrity. Multivariate modeling strategies were used to identify metabolites associated with unhealthy tissue as well as discover profiles common among all populations. Distinct metabolic fingerprints were established between symptomatic and healthy tissue. Elevated levels of ethanol and related ethyl esters may indicate diminished cellular integrity associated with symptoms and may be a basis for discriminating this disorder from other disorders. This diagnostic metabolic profile also is a step towards the ultimate goal of determining predictive metabolic biomarkers for soggy breakdown.