Search Results (260)

Postharvest lignification of juice sacs in Meizhou pomelo is a major physiological disorder that compromises fruit quality and limits sustainable industry development. Through a comprehensive three-year field study, we investigated the effects of key factors—soil organic matter, storage temperature, and tree age—on fruit lignification, and evaluated the efficacy of ten plant growth regulators (PGRs) and their combinations in mitigating granulation. Our results demonstrated that soil rich in organic matter and exchangeable calcium significantly reduced the granulation index. Constant storage at 15 °C effectively suppressed weight loss and lignification compared to fluctuating ambient temperatures. Among the tested PGRs, 28-Homobrassinolide (28-homo-BR), 28-Epihomobrassinolide (28-epi-BR), 24-Epibrassinolide (24-epi-BR), and 14-Hydroxybrassinosteroid (14-hydro-BR) exhibited the most pronounced effects in alleviating granulation. Two superior PGR combinations were subsequently identified, which functioned by synergistically downregulating the activities of key phenylpropanoid pathway enzymes—phenylalanine ammonia-lyase, 4-coumarate: CoA ligase, cinnamyl alcohol dehydrogenase, and peroxidase. This downregulation likely contributed to reduced lignin biosynthesis and accumulation. Metabolomic profiling further revealed an accumulation of phenylpropanoid precursors, including ferulic acid and p-coumaric acid, in lignified juice sacs, indicating that the overactivation of this pathway is a key metabolic feature associated with lignification. This finding provides critical evidence for the potential mechanism whereby PGRs suppress lignification, thus offering both mechanistic insights and practical strategies for controlling lignification in pomelo and other citrus fruits. Full article

The coordination between carbon and nitrogen metabolism is central to plant adaptation to water-limited environments. This study investigated how soil management practices modulate the metabolic and physiological performance of Citrus sinensis trees cultivated under semi-arid conditions. Six field treatments combining weed-control netting, subsurface drainage, and zeolite amendment were evaluated for their effects on vegetative growth, yield, and fruit metabolome. Using ¹H-NMR spectroscopy, 23 metabolites in peel and 21 in juice were identified and quantified, revealing that sugars, organic acids, and amino acids were the most responsive compound classes. Multivariate analyses (PCA, PLS-DA) showed distinct metabolic fingerprints associated with each soil management regime. Treatments integrating netting and zeolite (T4) induced a coordinated reprogramming of carbon and nitrogen metabolism, characterized by altered levels of glucose, fructose, citrate, and proline. These changes suggest enhanced osmotic regulation and tricarboxylic acid cycle activity, supporting improved water-use efficiency and physiological stability under semi-arid stress. The results demonstrate that soil management directly influences fruit metabolic homeostasis, linking environmental modulation of root-zone conditions with whole-plant biochemical adjustment. This integrative metabolomic approach provides mechanistic insight into how soil–plant interactions shape the metabolic resilience of citrus under water-limited field environments. Full article

The granulation of pomelo (Citrus maxima) juice sacs severely compromises fruit quality and is closely associated with lignin accumulation, a process catalyzed by peroxidases (PODs). Analysis of ‘Sanhong’ pomelo juice sacs collected 175–215 days after flowering revealed that bound peroxidase (BPOD) activity paralleled changes in lignin content, suggesting a potential role for BPOD in lignin biosynthesis. A total of 71 CmPOD genes were identified in the pomelo genome through integrated HMMER and BLAST analyses. Among them, CmPOD52 was selected for functional characterization based on its alkaline peroxidase properties, absence of a CE domain, predicted extracellular localization, and gradually increasing expression pattern revealed by RT-qPCR. Its transient overexpression in ‘Sanhong’ pomelo juice sacs for 36 h increased BPOD activity 2.06-fold (p < 0.01) compared to the empty vector control, indicating that CmPOD52 may be a BPOD gene. The recombinant CmPOD52 protein was expressed in a prokaryotic system, purified, and used in enzymatic assays with sinapyl alcohol as the substrate. The recombinant CmPOD52 protein, assayed at 272 nm with controls (substrate-only blank and heat-inactivated protein), showed an activity of 13.67 ± 0.9 U. The experimental group showed new products, identified by mass spectrometry as sinapyl alcohol dimers, thus suggesting that the recombinant protein catalyzes the dehydrogenation and polymerization of sinapyl alcohol monomers. This study identified CmPOD52, a gene potentially involved in lignin polymerization in pomelo juice sacs, offering a key candidate for further in vivo validation. Full article

Sinensetin, a polymethoxylated flavone abundant in citrus fruits, has been recognized for its broad biological activities and wide use in traditional medicine around the world. Emerging clinical evidence from flavonoid-enriched orange juice interventions indicates antioxidant and anti-inflammatory effects, aligning with extensive preclinical data. In this review, we explored in vitro and in vivo findings on the anti-inflammatory and anticancer actions of sinensetin and delineated the underlying cellular pathways, especially in terms of proposed targets for sinensetin. In inflammatory settings, sinensetin attenuates NF-κB activation, lowers pro-inflammatory cytokines (e.g., TNF-α, IL-6), and enhances antioxidant defenses, supporting its reported antioxidant, anti-bacterial, anti-viral, and anti-obesity properties. Across multiple tumor models, sinensetin suppresses oncogenic signaling—including β-catenin, PI3K/AKT, VEGF, NRF2, P53, and MKK6—concomitant with reduced proliferation, migration, and survival signaling. We further discuss emerging immunological effects, including modulation of innate immune cell activation and cytokine production, which may contribute to tumor microenvironment reprogramming and inflammation resolution. Together, these mechanistic insights position sinensetin as a promising lead for chemopreventive and adjunct therapeutic strategies. Our efforts aim to provide insights into the future translational development and clinical evaluation of sinensetin and its derivatives. Full article

Citrus species develop fruits through both sexual reproduction and parthenocarpy, following a growth pattern with an initial exponential phase dominated by cell division in the ovary wall, followed by a linear phase driven by cell expansion in juice vesicles. Sustained carbohydrate supply is essential to support the metabolic energy required for these processes, which are tightly regulated by hormonal signaling pathways involving gibberellins (GAs), auxins (IAA), cytokinins, and abscisic acid (ABA). Recent studies across cultivars have identified genes associated with hormone biosynthesis, carbohydrate metabolism, cell cycle regulation, and abscission in ovule and pericarp tissues. Manipulation of these hormones through targeted treatments and cultural practices has shown potential to enhance fruit set and growth. Notably, exogenous GA₃ application promotes fruit set in parthenocarpic cultivars by upregulating GA20ox2/GA3ox and CYCA1.1, whereas synthetic auxins enhance fruit enlargement by improving assimilate partitioning and water uptake. Optimizing such treatments, however, requires a comprehensive understanding of physiological, environmental, and agronomic factors influencing fruit development. This review summarizes recent advances in hormonal and molecular regulation of citrus fruit set and developments, assesses applied strategies to improve productivity, and identifies current knowledge gaps needed to refine biotechnological and management aimed at enhancing both yield and fruit quality. Full article

To address the contradiction between the widespread prevalence of selenium deficiency and the growing demand for selenium-enriched fruits, this study utilized phosphate tailings (industrial solid waste), wood vinegar (a by-product of forestry processing), biochemical fulvic acid, and alginic acid (renewable biomass resources) to construct an organic–inorganic composite soil selenium activator. This formulation enhances the mobilization of inherent selenium in the soil without relying on exogenous selenium supplementation, thereby improving selenium bioavailability while mitigating the environmental pollution and resource depletion associated with external selenium inputs. Through field experiments, we systematically evaluated the influence of varying activator dosages on soil physicochemical properties, available selenium content, selenium distribution in different citrus organs, and fruit quality. The results demonstrated that the application of the compound activator at 600 g/plant significantly increased (p < 0.05) soil available selenium and fruit selenium content by 21.26% and 21.06%, respectively. During the fruit expansion stage of Sugar Orange, soil available selenium was elevated by 21.8%, which corresponded to a 21.09% increase in fruit selenium content. Regarding fruit quality parameters, Sugar Orange exhibited increases in soluble solids (35.8%), citric acid (20.3%), solid-to-acid ratio (77.8%), and selenium content (223.3%). In Rock Sugar Orange, significant enhancements were observed in soluble solids (46.1%), vitamin C (45.3%), total soluble sugars (73.4%), solid-to-acid ratio (156.6%), and selenium content (69.7%). Structural equation modeling revealed that soil available selenium, soil properties, and selenium content in citrus organs collectively exerted positive regulatory effects on fruit quality. Specifically, juice selenium content showed significant positive correlations with fruit shape index, individual fruit weight, soluble solids content, and solid-to-acid ratio. This strategy achieves the synergistic reuse of industrial solid waste and agricultural biomass resources, offering a green and sustainable pathway to enhance selenium content and quality in citrus fruits. Full article

In the Yucatán Peninsula, Citrus aurantium L. has a strong cultural and culinary relevance where local industries already process its juice and essential oils, producing large amounts of by-products. In this context, green chemistry strategies have accelerated the valorization of agro-industrial residues, where Natural Deep Eutectic Solvents (NADESs) stand out due to their low cost, ease of preparation, and high extraction efficiency. This study focuses on evaluating different NADES combinations for the extraction of bioactive compounds from C. aurantium by-products, obtained after essential oil (cold pressing) and juice (mechanical pressing) extraction. A 3 × 2 × 2 factorial design was implemented to evaluate the effect of hydrogen bond donor (HBD: fructose, glucose and glycerol), molar ratio (MR: 1:1 and 1:2 mol/mol choline chloride (ChCl:HBD)) and added water (AW: 50 and 70%) on the polyphenolic profile, total phenolic content, total flavonoid content, ascorbic acid content and antioxidant capacity. HBD was the most critical factor in the extraction of bioactive compounds; the extract obtained with glycerol and 70% AW exhibited the highest hesperidin content (2186.08 mg/100 g dry mass), while the same HBD with 50% AW exhibited the highest quercetin + luteolin extraction (721.32 mg/100 g dry mass), both at the same MR (1:1 mol/mol). Glycerol also achieved the highest recovery of total flavonoids (1829.7 ± 17.85 mg quercetin equivalent/100 g dry mass) with an MR of 1:2 mol/mol and 70% AW. Finally, all other maximum values were obtained with fructose-based NADESs: the highest total phenolic content (3603. 7 ± 52.9 mg gallic acid equivalent/100 g dry mass) was achieved at an MR of 1:1 mol/mol and 50% AW, while for both vitamin C (1964.8 ± 33.7 mg ascorbic acid equivalent/100 g dry mass) and antioxidant capacity (84.31% inhibition), the maximum was reached at an MR of 1:2 mol/mol and 50% AW. Full article

This study provides the first comprehensive chemical and biological profiling of Citrus lumia Risso & Poit. var. ‘Pyriformis’, a rare Mediterranean Citrus variety with unexplored nutraceutical potential. The fresh juice (CLPJ) showed a distinctive phytochemical composition, with 38.8 ± 0.99 mg gallic acid equivalents/100 mL of total phenols and 25.96 ± 2.37 mg rutin equivalents/100 mL of flavonoids. High-performance liquid chromatography coupled with diode-array detection (HPLC-DAD) quantification revealed high levels of organic acids, including ascorbic acid (0.34 g/L) and citric acid (34.6 g/L). Liquid chromatography coupled with diode-array detection and electrospray ionization tandem mass spectrometry (LC-DAD-ESI-MS/MS) enabled the annotation of 28 polyphenolic constituents, featuring glycosylated flavanones and several uncommon flavonols and acylglycosidic derivatives whose structural patterns are typical of primitive Citrus lineages and largely absent in commercial cultivars. Functionally, CLPJ exhibited multi-target antioxidant and anti-inflammatory activities and promoted epithelial repair in Caco-2 cells without cytotoxic effects. Overall, the juice displays a distinctive chemotaxonomic fingerprint and promising multifunctional properties, supporting its potential as a functional food ingredient and contributing to the valorization of minor Mediterranean Citrus biodiversity. Full article

Cultivation practices such as fruit thinning and soil management with ground covers are commonly applied in Citrus orchards, yet their physiological impact on young trees remains poorly documented. This study evaluated the effects of manual fruit thinning and weed-control mesh on vegetative growth, fruit development, and leaf mineral composition of Citrus sinensis L. Osbeck cv. ‘Navelina’ grafted on Citrus macrophylla. A six-month field experiment was conducted in southeastern Spain under semi-arid Mediterranean conditions using six treatments that combined different soil coverage and subsurface drainage systems. After physiological fruit drop, trees were standardized to ten fruits per plant. Vegetative parameters (canopy and trunk dimensions), fruit growth (size, juice content), and foliar nutrient concentrations were monitored. Trees with ground cover showed significantly greater canopy expansion and juice yield compared to uncovered controls. A negative correlation between fruit number and canopy-to-fruit volume ratio highlighted the trade-off between vegetative vigor and fruit load. Foliar analysis revealed lower micronutrient concentrations (Fe, Mn, B, Zn) in uncovered trees, suggesting reduced nutritional status. These findings demonstrate that combining early thinning with weed-control mesh promotes vegetative vigor, improves juice yield, and enhances nutrient uptake, providing practical insights for optimizing orchard establishment and early Citrus productivity in water-limited environments. Full article

Citrus fruit processing, mainly for fresh juice production in the food industry, generates significant amounts of residues and by-products enriched with bioactive components. Peels are the primary waste fraction of citrus fruits, along with discarded pulp and seeds. This study aimed to identify the most fast and sustainable extraction process for flavonoids on a laboratory scale by varying the solvent and extraction methodology, and comparing the yields in order to evaluate their influence on total and individual flavonoid content. A chromatographic analysis was also performed using ultrahigh-performance liquid chromatography (UHPLC) with a 10 min run time. Our focus was on selecting the most user-friendly and cost-effective methodology. Ultrasound- and microwave-assisted extraction equipment were used with green solvents (water and ethanol) and compared for their efficiency in recovering flavonoid compounds from a mixture of peel and pulp. For this study, two widely cultivated Mediterranean citrus varieties were selected: ‘Marsh’ seedless grapefruits (Citrus paradisi Macf.) and ‘Comun’ mandarins (C. deliciosa Ten.). Lab-scale extraction results showed that ultrasound-assisted extraction with a simple ultrasonic bath, using an ethanol–water mixture provided the highest total flavonoid recovery and improved the extraction of key flavanones such as hesperidin, narirutin, and naringin. All ethanol–water mixtures tested (1:1, 7:3, and 3:7) yielded higher flavonoid levels in grapefruit (approximately 2500 mg/100 g DW) and mandarin (approximately 1200 mg/100 g DW) wastes compared with water or ethanol alone. This method offers a scalable and green strategy for valorizing citrus residues. Full article

‘Pera’ sweet orange is a key variety for the Brazilian citrus industry, but orchards rely on a limited number of clonal selections, which restricts adaptability and productivity across diverse environments. This study assessed the agronomic performance of 13 ‘Pera’ selections grafted on Rangpur lime, cultivated under rainfed conditions in subtropical Brazil. From 2002 to 2010, trees were assessed for vegetative growth, cumulative yield, alternate bearing, and fruit quality. Market-specific performance indices were calculated to determine suitability for fresh fruit or juice processing. Substantial genotypic variation was observed across traits, particularly during early orchard stage. Selections such as ‘Morretes’, ‘Seleção 11’, ‘Seleção 27’, ‘Seleção 37’, and ‘IPR 153’ demonstrated high cumulative yield, stable productivity, and favorable canopy traits, supporting their use in both conventional and high-density systems. ‘IPR 153’ combined compact growth with high yield efficiency and excellent fruit quality, while ‘Morretes’ had the highest juice content and broad market adaptability. In contrast, ‘IPR 159’ showed low vigor and yield under rainfed conditions. The results emphasize the value of regionally targeted clonal selection to improve orchard performance and market alignment. The identification of dual-purpose genotypes offers a pathway to diversify citrus production and improve profitability under subtropical growing conditions. Full article

The global citrus industry faces unprecedented challenges due to Huanglongbing (HLB), which is associated with the bacterial pathogen Candidatus Liberibacter asiaticus (CLas). This study evaluates the field performance of 11 rootstocks, grafted with ‘Valencia’ orange (Citrus sinensis), under Florida’s HLB-endemic production conditions, while also examining the impact of systemic applications of oxytetracycline (OTC) via trunk injection. Mature trees received annual OTC injections and were assessed over two production seasons. In year 1, OTC-treated trees exhibited significant improvements regardless of the rootstock, including a 36% increase in yield, an 11% increase in juice TSS, and reduced leaf bacterial titers. During year 2, the positive effects of OTC were sustained, or even enhanced. CLas titers were reduced in both leaves and roots; yield increased by 70%; and fruit weight, juice color, and TSS also improved significantly. Moreover, OTC-injected trees exhibited a larger percentage of finer roots compared to non-injected trees. US-1688 and US-1672, both hybrids of C. maxima ‘Hirado’ and C. reticulata ‘Cleopatra’, emerged as the most productive rootstocks. These results demonstrate the importance of rootstock selection for sustainable citrus cultivation while highlighting the benefits of integrating the systemic delivery of OTC to manage HLB and maximize the resilience of citrus. Full article

Silicon (Si) is gaining recognition as a sustainable alternative to reduce insecticide use in the management of the Asian citrus psyllid and huanglongbing (HLB). This study aimed to evaluate the effects of two silicon sources and three application methods on Diaphorina citri incidence, soil chemical properties, and foliar nutrient uptake in a Tahiti lime orchard. Using a randomized block design, treatments were applied six times over three months. Foliar and combined applications of diatomaceous earth reduced vegetative flushing and decreased natural psyllid incidence by up to 75% in the first 30 days. While silicon did not affect oviposition in induced infestations, it disrupted the nymph-to-adult transition. Silicon also improved soil conditions, increasing pH, organic matter, and the availability of phosphorus, calcium, and magnesium. In leaf tissue, higher levels of nitrogen, phosphorus, potassium, iron, and silicon (0.28–0.50%) were observed. Fruit quality improved with silicon, showing greater fresh weight (134 g) and juice content (44.7%) compared to the control (95.33 g and 28.5%). The results suggest that silicon’s effectiveness depends more on its availability and application method than its source. Incorporating silicon, especially diatomaceous earth, into fertilization programs supports pest control, enhances soil and plant nutrition, and improves fruit quality. Full article

The systemic delivery of oxytetracycline (OTC) by trunk injection has emerged as a viable strategy to manage huanglongbing (HLB, also known as citrus greening), a bacterial disease devastating citrus production around the world. This study examines the efficacy of delivering OTC systemically into the trunk of young, HLB-affected citrus trees using a drill-based or a drill-free system to improve tree health and productivity. Two field trials were conducted in two commercial production sites in Florida. Trees were four years old at the start of the study and composed of ‘Valencia’ or ‘OLL-8’ sweet orange (Citrus sinensis) scion grafted on X-639 (C. reticulata × Poncirus trifoliata) rootstock. Injections were performed in spring or late summer/early fall in 2022 and 2023. Using the drill-based system, 0.79 g of OTC was administered into each tree, whereas 0.15 g or 0.3 g was administered using the drill-free system. Delivering a higher dose of OTC by drill-based injection increased fruit yield and improved juice quality more than delivering lower doses by drill-free injection, though responses varied between cultivars. Injections in late summer/early fall increased the juice total soluble solids content considerably more than injections in spring. However, fall injections resulted in OTC fruit residues exceeding the maximum allowed level. Trunk injury was more extensive when OTC was applied with the drill-free system than when it was applied with the drill-based system. Full article

The blood orange arose from the insertion of a retrotransposon adjacent to the Ruby gene, an MYB-type transcriptional activator of anthocyanin production, as reported previously. However, the intricate process of anthocyanin regulation among different varieties of blood orange remains incompletely understood. In this study, mRNA levels of the transcription factors Ruby and TT8 were found to be upregulated in the juice vesicle tissues of a variety with higher concentrations of anthocyanins in the pulp compared with another variety with a lower anthocyanin content. In contrast, comparative analysis of the two varieties using two-dimensional electrophoresis and mass spectrometry did not identify differentially expressed proteins related to anthocyanin biosynthesis in the juice vesicle tissues. Furthermore, higher anthocyanin contents were observed in various tissues of transgenic Arabidopsis thaliana overexpressing the Ruby gene from blood orange compared with the wildtype plant. Moreover, the long terminal repeat (LTR) region of a retrotransposon inserted upstream of the Ruby locus exhibited the ability to drive reporter expression through histochemical assay in a transgenic seedling. Thus, a PCR-based molecular marker was developed, targeting the upstream sequence of the Ruby locus to identify Citrus hybrids with the unique trait of red-fleshed fruit. Intriguingly, bisulfite sequencing revealed differentially methylated regions within a Gag-Pol polyprotein-encoding sequence of a retrotransposon adjacent to Ruby locus when comparing two varieties with different anthocyanin contents. A higher average level of methylation status was observed in the fruit with a lower anthocyanin content. In conclusion, methylation modifications at specific upstream positions on the Ruby locus may influence anthocyanin production in blood oranges. Full article