Fatty acid metabolism and hydrogen peroxide accumulation are associated with skin greasiness development in apple fruit

Skin greasiness is an undesirable postharvest quality defect that can develop in apple fruit (Malus domestica Borkh.) during storage, reducing commercial value by causing excessive surface gloss and a greasy texture. However, the molecular mechanisms underlying its development remain poorly understood. This study investigated the physiological and metabolic factors associated with skin greasiness in apple fruit through metabolomic, transcriptomic, and physiological analyses of two cultivars, ‘Hongro’ (HR) and ‘Fuji’ (FJ). During storage, HR fruit developed pronounced skin greasiness and exhibited higher ethylene production, whereas FJ fruit showed no visible greasiness. HR fruit accumulated higher levels of unsaturated fatty acids and fatty acid alkyl esters, along with transcriptional regulation of genes involved in fatty acid metabolism ( ENR1 , FATA1 , FAD2 , and FAD2-like ) and wax transport ( LTPG1-like and LTPG11-like ). In contrast, these metabolic changes were relatively limited in FJ fruit. Transcriptomic analysis further revealed differential expression of genes associated with hydrogen peroxide (H 2 O 2 ) responses, with greater H 2 O 2 accumulation in HR than in FJ. Moreover, exogenous H 2 O 2 treatment accelerated greasiness development in HR fruit accompanied by increased early ethylene production, respiration rate, and the expression of genes related to fatty acid metabolism and wax transport. Collectively, these results suggest that differential regulation of fatty acid metabolism contributes to the contrasting greasiness phenotypes of HR and FJ fruit during storage, whereas H 2 O 2 -associated responses may be involved in the metabolic and physiological changes accompanying greasiness development in HR.