Background: Citrus paradisi Mac. cv. Cocktail is globally valued for its abundant nutrients and bioactive compounds, particularly in tropical and subtropical regions. A novel albino phenotype mutant of C. paradisi Mac. cv. Cocktail (designated WT) was identified in Quzhou and subsequently named C. paradisi Mac. cv. Cocktail mosaic mutant (MT). To distinguish C. paradisi Mac. cv. Cocktail from conventional grapefruit cultivars and to elucidate genomic differences between WT and MT, this study conducted a comprehensive comparison of their chloroplast genomes with those of previously reported Citrus species. Methods: The complete chloroplast genomes of WT and MT were assembled through Illumina PE150 sequencing, enabling detailed comparative genomic and evolutionary studies. Results: The results revealed that both WT and MT chloroplast genomes exhibit a conserved quadripartite structure. Each genome measures 160,186 base pairs in length, with a uniform GC content of 38.5%. Annotation revealed 138 genes (91 protein-coding, 10 rRNA, 37 tRNA), 82 repeats, and A/U-biased codons. Genome boundaries and genome comparison showed WT and MT were identical but divergent from other Citrus. The 52 conserved protein-coding genes showed comparable selection pressures in both WT and MT. Phylogenetically, WT and MT are closely related and are distinguished from all of the traditional grapefruits. Conclusions: The albino phenotype of MT is unrelated to chloroplast variations. Chloroplast genomics supports C. paradisi cv. Cocktail’s differentiation from conventional grapefruits. This study expands the chloroplast genomic resources for Citrus and establishes a theoretical framework for future research on C. paradisi cv. Cocktail and related varieties.

Polyploidy modifies metabolic profiles and transcriptional regulation of biosynthetic pathways. Citrus tetraploids are characterized by dwarf growth and increased leaf biomass. Citrus leaves are valuable resources for essential oils and natural food additives because of their rapid regrowth, high biomass yield, and year-round availability. In this study, 11 spontaneous autotetraploids (1.14%) were identified among 967 yuzu seedlings. Compared with diploids, tetraploids exhibited reduced plant height, wider leaves, and fewer but larger stomata, accompanied by a 70% increase in net photosynthetic rate and a 2.6-fold increase in stomatal conductance. Volatilomic analysis showed that only 12.4% of the 920 detected volatile organic compounds (VOCs) differed significantly between ploidy levels; notably, two esters—methyl 2-(methylamino) benzoate and 2-methoxyethyl benzoate—were substantially enriched in tetraploids (~400-fold and ~8-fold, respectively). Nonvolatile metabolomic analysis revealed higher accumulation of bioactive coumarins (e.g., bergapten, imperatorin, and isopimpinellin) and lower levels of flavonoids in tetraploid leaves. Transcriptomic analysis indicated enrichment of genes involved in flavonoid and coumarin biosynthesis. Integrated multi-omics analysis demonstrated that upregulation of psoralen synthase (PS) and scopoletin 8-hydroxylase (S8H) was positively associated with increased coumarin accumulation, whereas downregulation of flavonol synthase (FLS) and flavonol-3-O-glucoside L-rhamnosyltransferase (FG2) contributed to reduced flavonoid content, indicating a metabolic shift from flavonoids to coumarins in tetraploid leaves. These findings provide insight into secondary metabolite reprogramming following autotetraploidization in yuzu and highlight its potential value for the bioactive coumarin industry.

To evaluate the suitability of different citrus varieties for making green mandarin tea and thus expand its raw‐material base, immature fruits of Chachiensis (Citrus reticulata blanco cv. Chachiensis), Ponkan (Citrus reticulata blanco cv. Ponkan), Quju (Citrus reticulata “Quju”), Yuzu (Citrus junos Sieb. ex Tanaka), and Unshiu (Citrus reticulata “Unshiu”) were used as peels and coprocessed with black tea via a sun‐drying plus hot‐air protocol. We systematically compared their volatile profiles, sensory attributes, and nutritional quality. Gas chromatography‐mass spectrometry (GC‐MS) showed that products based on Chachiensis, Quzhou Ponkan, and seedless Ponkan shared similar aroma compositions dominated by D‐limonene and γ‐terpinene. In contrast, the Yuzu‐based product uniquely contained spathulenol and α‐copaene, yielding a characteristic aroma spectrum. Sensory evaluation indicated that the Yuzu‐based product achieved the highest overall score (75.28/100), with well‐balanced flavor and a lasting sweet aftertaste; Ponkan‐based products also performed well. In the nutritional assessment, the Yuzu‐based product had the highest water extract, whereas Ponkan‐based products exhibited significantly higher total flavonoid and total phenol contents than the other groups. Collectively, Ponkan and Yuzu emerge as favorable source materials for green mandarin tea, excelling in nutritional value and distinctive flavor, respectively.