Analysis of heaping-induced decline in olive quality: insights from integrated analysis between phenotypic traits and gene expression profiles

Abstract Heaping is an unavoidable process before olive milling, and its duration significantly affects the olive quality. However, there is limited research on the quality changes of olive fruits on a short-time scale. To gain a better understanding of the molecular mechanisms underlying postharvest deterioration of olives, this study piled olives at room temperature and extracted oil at 0, 8, 24, 48 and 72 h to analyze oil quality parameters. Gas/Liquid Chromatography-Mass Spectrometry (GC/LC–MS) techniques were employed to investigate variations in metabolite contents. Concurrently, the transcriptional profiles of olives during heaping were examined. As piling time progressed, quality indicators declined, and stored fruit were categorized into three groups based on their quality characters: ‘0 h’ belongs to the first category, ‘8 h’ and ‘24 h’ to the second category, and ‘48 h’ and ‘72 h’ to the third category. Metabolite changes were consistent with the expression patterns of genes related to their synthesis pathways. Additionally, ethylene was identified as a crucial factor influencing fruit senescence. These findings establish a foundation for further research on olive deterioration after harvesting and offer insights for optimizing olive oil production.