Most sweet cherry varieties exhibit typical gametophytic self-incompatibility (GSI) characteristics, necessitating careful configuration of pollination trees to ensure adequate yields. This requirement increases the costs associated with orchard labor, management, and other related expenses. Consequently, cultivating and developing sweet cherry cultivars with self-compatibility can effectively address these challenges. Research into the molecular mechanisms underlying GSI formation can provide vital theoretical support and genetic resources for breeding self-compatible sweet cherries. In this study, we assessed the fruit set rates of ‘Tieton’ following both self- and cross-pollination. Additionally, we conducted a transcriptome analysis of the ‘Tieton’ style (which includes the stigma) at 0, 12, 24, and 48 h post-pollination to identify key genes involved in the self-incompatibility process of sweet cherries. The results indicated that the self-fruiting rate of ‘Tieton’ was significantly lower than that of cross-pollination. We identified a total of 8148 differentially expressed genes (DEGs) through transcriptome analysis, with KEGG pathway analysis revealing that the plant-pathogen interaction, plant hormone signal transduction, and plant MAPK signaling pathways were primarily involved in sweet cherry GSI. Furthermore, we identified 13 core transcription factors (TFs) based on their differential expression patterns, including three ERFs, three NACs, three WRKYs, two HD-ZIPs, one RAV, and one MYB. Co-expression analysis identified 132 core DEGs significantly associated with these TFs. Ultimately, this study provides initial insights into the key genes within the sweet cherry GSI network, laying a theoretical foundation and offering genetic resources for the future molecular design breeding of new self-compatible varieties.

Jasmonate ZIM-domain (JAZ) family genes, which belong to TIFY family, are plant-specific transcriptional repressors. As key regulators of the jasmonic acid signaling pathway, JAZ proteins play crucial roles in various aspects of plant biology. However, the identification and functional characterization of JAZ genes in sweet cherry (Prunus avium L.) fruit remain unknown. In the present study, we identified nine JAZ members in the sweet cherry genome. We systematically analyzed the gene structures, protein domains, evolutionary relationships, and physicochemical properties of these members and also evaluated their expression levels across different fruit developmental stages, as well as under methyl jasmonate (MeJA) treatment. Among these members, our results revealed a previously uncharacterized JAZ member, PavJAZ8, as a crucial regulator of fruit aroma traits. Specifically, RT-qPCR analysis showed that PavJAZ8 overexpression modulates the expression of genes involved in the biosynthesis of aroma volatiles, such as PavLOX2, PavLOX3, PavHPL1, PavADH1.1, PavADH1.2, and PavADH7, which are involved in the synthesis of aldehydes and alcohols. Consistent with the gene expression data, analysis of volatile metabolites revealed that PavJAZ8 overexpression significantly inhibited the accumulation of several related aldehydes and alcohols, including hexanal, geraniol, and benzyl alcohol. Furthermore, PavJAZ8 expression was highly responsive to phytohormone treatments, such as abscisic acid (ABA) and MeJA. Further analysis showed that PavJAZ8 interacts with PavMYC2, thereby mediating JA signal transduction. Our results highlight PavJAZ8 as a novel regulator of fruit aroma quality, offering a valuable genetic target for sweet cherry improvement.

Cold storage induces flavor deterioration in sweet cherry, while cultivar-specific regulatory mechanisms are poorly understood. In this study, two mainstream commercial cultivars, ‘Rainier’ and ‘Tieton’, were stored at 4 °C for 21 days. We comprehensively integrated physiological phenotyping, transcriptomics, metabolomics, and volatile compound profiling to explore their flavor deterioration patterns. Physiological results demonstrated that fruit softening and sugar-acid imbalance were typical deterioration symptoms, and ‘Tieton’ reached a 100% decay rate at the end of storage, far higher than 51.55% of ‘Rainier’. Metabolomic analysis identified 1876 metabolites, and the two cultivars showed asynchronous metabolic reprogramming. ‘Tieton’ underwent dramatic metabolic changes at the early storage stage, while obvious metabolic shifts occurred in ‘Rainier’ at the mid stage. “Starch and sucrose metabolism” and “phenylpropanoid biosynthesis” were confirmed as two universally core pathways associated with flavor variation. We also detected 45 differential volatile compounds linked to fruit aroma. Furthermore, a flavor regulatory network was constructed, verifying that PavMYB3/13 as candidate positive regulators and PavC2H2 is a candidate negative regulator of flavor maintenance. This work elaborates on the genotype-specific patterns of cold-induced flavor decay and provides a theoretical foundation for developing variety-targeted postharvest preservation technologies for sweet cherries.

Sweet cherries are an important temperate fruit crop, and protected cultivation has expanded rapidly in recent years. However, unstable fruit set under protected cultivation remains a major challenge, and the application of fruit set enhancement treatments has become common practice in commercial production to stabilize and improve fruit set performance. Various fruit set enhancement treatments, including biotic pollination and hormonal regulation, have been shown to influence source–sink relationships through different physiological pathways, thereby affecting fruit set rate and fruit quality. In this study, three fruit set enhancement treatments, namely hand pollination (HP), plant growth regulator treatment (PGRT), and bee pollination (BP), were applied, with an untreated control (CK) included for comparison, to evaluate their effects on fruit set rate and fruit quality in the self-compatible sweet cherry cultivar ‘Sunburst’ under protected cultivation. Both HP and PGRT significantly increased fruit set rate by 33.47 and 27.84 percentage points, respectively, compared with CK (71.68% and 66.05% vs. 38.21% in CK), and enhanced fruit firmness (86.50 g and 97.00 g vs. 70.10 g in CK) and raffinose content (0.53 mg g⁻¹ FW and 0.32 mg g⁻¹ FW vs. 0.15 mg g⁻¹ FW in CK). However, PGRT significantly increased pedicel length (3.43 cm vs. 2.81 cm in CK) and gluconic acid content (3.44 mg g⁻¹ FW vs. 2.02 mg g⁻¹ FW in CK), while decreasing ascorbic acid content (0.23 mg g⁻¹ FW vs. 0.34 mg g⁻¹ FW in CK). Although BP resulted in the highest soluble solids content (16.68%) and total phenolic content (1.93 mg g⁻¹), its fruit set rate remained low (42.06%) and was not significantly different from that of CK. Comprehensive evaluation indicated that, whilst ensuring adequate fruit set, hand pollination demonstrated superior overall performance among the evaluated treatments by maintaining desirable fruit appearance and balanced sugar–acid metabolism, serving as a practical, non-chemical, and environmentally safe supplementary fruit set enhancement strategy under the specific greenhouse conditions evaluated.