This study aimed to elucidate the differentiation patterns of aroma metabolism during fruit development across distinct peach flesh types, and identify key regulatory genes governing cultivar-specific aroma profiles, so as to provide a theoretical basis for flavor improvement in stony hard peaches.

The melting-flesh cultivar Chunmei and the stony hard cultivar Zhongtao 9 were utilized as experimental materials. Seven critical sampling stages were established throughout the fruit development cycle. Volatile compounds were profiled using headspace solid-phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS). Transcriptome sequencing was performed to identify differentially expressed genes (DEGs), and Pearson correlation analysis was employed to pinpoint core genes significantly associated with key aroma compounds.

A total of 57 volatile compounds were identified, with significant variation in composition and content across cultivars and developmental stages. The stony hard cultivar Zhongtao 9 exhibited no detectable ethylene production throughout development, maintained high levels of C6 aldehydes (e.g., 2-hexenal) at the mature stage, and showed almost no accumulation of esters and lactones. In contrast, the melting-flesh cultivar Chunmei exhibited a typical ethylene climacteric peak at the S3 to S4 transition, accompanied by a 3.1-3.8 fold increase in ester content and a marked decrease in C6 compounds. Transcriptome analysis identified 2806 DEGs, with clear separation between the two cultivars at all developmental stages based on clustering analysis. KEGG enrichment analysis indicated that these DEGs were significantly involved in plant hormone signal transduction, α-linolenic acid metabolism, and carotenoid biosynthesis pathways. Correlation analysis identified 16 candidate genes associated with ester/lactone biosynthesis. Among them, BSK2 (Prupe.2G110200) and PpYUC11 (Prupe.6G157400/6G157500) showed strong positive correlations with hexyl acetate and γ-decalactone, respectively.

Ethylene was a key regulatory factor underlying aroma quality divergence between the two peach flesh types. Impaired ethylene signaling in Zhongtao 9 likely restricted fatty acid metabolism at the C6 aldehyde stage, preventing downstream esterification and lactone biosynthesis. Candidate genes, such as BSK2 and PpYUC11, together with hormone signaling pathways, were identified as potential regulators of aroma formation.