Sugar content is a critical indicator of fruit quality and is mainly controlled by sugar transporters. Sugars will eventually be exported transporters (SWEET) proteins play an indispensable role in sugar allocation between and within plant organs. Sucrose is the major sugar in many fruits and the predominant form of sugar translocated in peach (Prunus persica). However, the role of the multiple peach SWEET genes in sucrose allocation to fruit remains elusive. In this study, a total of 19 SWEET candidates have been identified in the peach genome, and two Clade III SWEET genes, PpSWEET9a and PpSWEET14, are found to be highly expressed in mature source leaves and branches. Complementation assays, transgene manipulations, and protein interaction studies reveal that PpSWEET9a and PpSWEET14 serve as sucrose efflux proteins and form a heterooligomer that synergistically directs sucrose allocation from source leaves to fruits. Our findings provide insights into the effect of SWEETs on sugar accumulation in peach fruit and identify genetic candidates for improving fruit quality.

Peach fruit flesh spongy tissue disorder causes dry, porous, and brown areas in the flesh, severely compromising fruit quality and market value. While soil properties and calcium nutrition have been linked to the disorder, the role of rhizosphere microbial communities in disorder resistance remains unclear. This study investigated both the physicochemical properties and the root-associated microbiomes of disordered (CK) and healthy (TT) peach orchards to explore microbial mechanisms underlying disorder suppression. TT soils exhibited higher pH, greater organic matter, increased exchangeable calcium, and more balanced trace elements compared to CK. Microbial analysis revealed significantly higher diversity and enrichment of beneficial taxa in TT associated with plant growth and disorder resistance. Functional gene prediction showed TT was enriched in siderophore production, auxin biosynthesis, phosphate solubilization, and acetoin–butanediol synthesis pathways. Co-occurrence network analysis demonstrated that TT harbored a more complex and cooperative microbial community structure, with 274 nodes and 6013 links. Metagenomic binning recovered high-quality MAGs encoding diverse resistance and growth-promoting traits, emphasizing the ecological roles of Gemmatimonadaceae, Reyranella, Nitrospira, Bacillus megaterium, and Bryobacteraceae. These findings highlight the combined importance of soil chemistry and microbiome structure in disorder suppression and provide a foundation for microbiome-informed soil management to enhance fruit quality and promote sustainable orchard practices.

Peach (Prunus persica) fruit pigmentation is largely associated with anthocyanin accumulation, whereas colorless flavonols such as kaempferol glycosides may reflect alternative use of shared flavonoid precursors. To examine the relationship between anthocyanin and selected kaempferol glycoside accumulation, we analyzed 15 peach accessions classified by red, white, or yellow flesh pigmentation. Skin color was quantified using the a*/b* ratio, where a* represents redness/greenness and b* represents yellowness/blueness. Red-fleshed accessions showed higher skin a*/b* values and accumulated higher levels of total anthocyanins, particularly cyanidin-3-glucoside, than white and yellow accessions. In contrast, kaempferol-3-rhamnoside preferentially accumulated in white-fleshed accessions. Expression analysis of flavonoid pathway genes showed that dihydroflavonol 4-reductase (PpDFR) was more highly expressed in red accessions, whereas flavonol synthase (PpFLS) was more highly expressed in white accessions; chalcone synthase (PpCHS), flavanone 3-hydroxylase (PpF3H), flavonoid 3′-hydroxylase (PpF3′H), and anthocyanidin synthase (PpANS) showed no significant differences among color groups. Heterologous overexpression of PpF3′H in Arabidopsis thaliana, a well-characterized model plant for flavonoid biosynthesis, was associated with increased seed anthocyanin accumulation and a lower kaempferol-to-quercetin ratio, supporting its catalytic capacity to influence flavonoid composition in an exogenous system. Overall, these results indicate that differential anthocyanin and selected kaempferol glycoside accumulation in peach is associated with the relative expression patterns of branch-related flavonoid genes, particularly PpDFR and PpFLS. This study provides targeted metabolic and transcriptional evidence for understanding peach flesh and skin pigmentation and provides mechanistic insight into flavonoid branch competition linking gene expression patterns with metabolite allocation, and identifies candidate genes for improving fruit color and flavonoid-related nutritional quality.