2018 ASHS Annual Conference

Superficial scald is a peel browning of susceptible cultivars, such as ‘Granny Smith’ developing during prolonged cold storage. The ethylene perception inhibitor 1-methylcyclopropene (1-MCP) and the antioxidant diphenylamine (DPA) are used to effectively manage the disorder. The current study identifies changes in peel metabolism that are associated with the development of superficial scald throughout storage. Postharvest applications of 1-MCP and DPA were performed on ‘Granny Smith’ apples, and peel tissue was collected following harvest and throughout six months of storage. Nonpolar metabolites were extracted and analyzed using LC-MS and GC-MS to characterize metabolic divergence between control and treated fruit. Sesquiterpenes, α-farnesene oxidation products (conjugated trienols), sesquiterpene esters, and p-coumaryl esters differentially accumulated among control, DPA, and 1-MCP treated apples. Conjugated trienols were produced in high levels in control fruit prior to the development of visible scald symptoms as compared with DPA and 1-MCP treated fruit; this trend was also reflected in two compounds identified as fatty acyl esters of conjugated trienols. Levels of fatty acyl esters of p-coumaryl alcohol increased throughout storage; accumulation was greater in DPA treated peel and diminished in 1-MCP treated peel as compared with controls. Compounds tentatively identified as p-coumaryl conjugates of triterpenoic alcohols displayed the opposite trend, accumulating at higher levels in 1-MCP treated peel. Widespread changes in the metabolic profile of epidermal and wax layers indicate that changes in cellular dynamics and cuticle properties may both play a role in the development of superficial scald.