Title: Chilling-related cell damage of apple (Malus x domestica Borkh.) fruit cortical tissue impacts antioxidant, lipid, and phenolic metabolism Authors
|Ines, Hanrahan -|
|Watkins, Christopher -|
|Gapper, Nigel -|
|Johnson, Jason -|
|Schaffer, Robert -|
|Hertog, Maarten -|
|Nicolai, Bart -|
Submitted to: Physiologia Plantarum
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 14, 2014
Publication Date: N/A
Interpretive Summary: Soggy breakdown of ‘Honeycrisp’ apples is responsible for significant annual storage losses of this highly planted apple variety. This postharvest disorder results in large areas of dark brown water-soaked flesh and is attributed to postharvest refrigeration of fruit that are predisposed to developing the disorder. As the disorder is provoked by storage conditions and is orchard specific, we are evaluated changes in fruit chemistry that are associated with the period leading up to the appearance of the disorder as well as the disorder itself. Our results indicate changes in specific biochemical pathways are indicative of higher disorder risk during the period prior to disorder appearance and report a biochemical fingerprint for this specific disorder.
Technical Abstract: ‘Soggy breakdown’ (SB) is an internal disorder of ‘Honeycrisp’ apple (Malus × domestica Borkh.) fruit which occurs during low temperature storage. The disorder is a chilling injury (CI) in which visible symptoms typically appear after several weeks of storage, but information about the underlying metabolism associated with its incidence and development is lacking. The metabolic profile of flesh tissue from healthy fruit, and brown and healthy appearing tissues from the fruits affected by SB was characterized using GC-MS and LC-MS. Partial least squares discriminant analysis (PLS-DA) and correlation networks reveal correlation among ester volatile compounds by composition and differences in phytosterol, phenolic, and putative triacylglyceride (TAG) metabolism among the tissues. ANOVA-simultaneous component analysis (ASCA) was used to test the significance of metabolic changes linked with tissue health status; statistically significant components antioxidant compounds, TAGs and phytosterol conjugates. Relative to entirely healthy tissues, elevated metabolite levels in symptomatic tissue included '-amino butyric acid glycerol, sitosteryl (6’-O-palmitoyl) ß-D-glucoside and sitosteryl (6’-O-stearate) ß-D-glucoside and TAGs containing combinations of 16:0, 18:3, 18:2, and 18:1 fatty acids. Metabolite levels that decreased in soggy breakdown tissue included chlorogenic acid (5-caffeoyl quinate), ß-carotene, catechin, epicatechin, a-tocopherol, violaxanthin, and sitosteryl ß-' glucoside, compared with healthy fruit tissue. Pathway analysis indicated aspects of primary metabolism differed according tissue symptoms, although differences in metabolites involved were more subtle than secondary metabolites detected. The results implicate oxidative stress and membrane disruption processes in SB development, and constitute a diagnostic metabolic profile for the disorder.