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Citrus trees require a balanced and adequate supply of macronutrient and micronutrient elements for high yield and fruit quality. Foliar nutrient analysis has been widely used in fruit-tree nutrient diagnosis and fertilization calculation. However, there is no information on ways to produce optimal fruit quality in sweet oranges. In the present study, fruit and leaf samples were collected from 120 'Bingtang' sweet orange [Citrus sinensis (L.) Osbeck] orchards during four consecutive years (2019–2022). Parameters of leaf nutrition and fruit quality were analyzed based on these samples. Diagnostic results based on leaf classification standards indicated that the most deficient elements were Ca, Mg, and B, followed by N and Zn. Fruit quality, determined by single fruit weight (SFW), fruit shape index (FSI), total soluble solids (TSS), titratable acidity (TA), vitamin C (Vc), and maturation index (MI = TSS/TA) during fruit maturation, exhibited inconsistent responses to leaf mineral nutrition concentrations. The leaf-nutrient optimum values for high quality of the 'Bingtang' sweet orange fruit were ranges of 2.41–4.92% N, 0.10–0.28% P, 1.30–2.11% K, 2.99% Ca, 0.26–0.41% Mg, 340–640 mg/kg S, 89.65–127.46 mg/kg Fe, 13.48–51.93 mg/kg Mn, 2.60–13.84 mg/kg Cu, 15.59–51.48 mg/kg Zn, and 53.95 mg/kg for B. These results suggest the leaf-nutrient optimum values for diagnosis can be used not only to identify the nutrient constraints but also to provide guidance for the establishment of fertilization regimes in citrus cultivation. [ABSTRACT FROM AUTHOR]

In the winter season, citrus nursery production faces challenges including shorter days, lower light levels, and lower temperatures that delay vegetative budbreak and scion shoot growth. With the goal of improving the production cycle in the citrus nursery, we investigated the effect of supplemental LED light on the production of bud-grafted citrus trees during short winter days. Three experiments were conducted under different temperature conditions. "Washington" Navel sweet orange (Citrus sinensis) was budded on Carrizo citrange (C. sinensis × Poncirus trifoliata) and Rubidoux trifoliate (P. trifoliata) rootstocks in early December. Light treatments included no supplemental light, day-length extension to 16 h with LED light, and night interruption (1 h of LED light at night). Day-length extension and night interruption were studied with and without preconditioning plants with the respective light treatments for 6 weeks before grafting. Day-length extension increased the scion growth, but only when supplemental heating was provided, implying that low temperatures are a limiting factor for plant growth. Growth effects were stronger when the Navel scion was grafted on Carrizo compared to Rubidoux, likely because of the higher dormancy of the latter rootstock. Night interruption did not affect scion budbreak or growth under any of the tested conditions. Preconditioning enhanced scion growth in some instances. The results suggest that the use of supplemental LED light to extend the day length may increase plant growth during the short winter days, but the effects are limited under low-temperature conditions. [ABSTRACT FROM AUTHOR]

Reactive oxygen species (ROS) are pivotal in signal transduction processes in plant–pathogen interactions. The ROS signaling pathways involved in Candidatus Liberibacter asiaticus (CLas) and Xanthomonas citri subspecies citri (Xcc) infections in Citrus sinensis (sweet orange) are unclear. In this study, we comprehensively identified ROS metabolism-associated genes, including 9 NADPH oxidase (RBOH), 14 superoxide dismutase (SOD), 1 catalase (CAT), 9 peroxiredoxin (PrxR), 5 ascorbate peroxidase (APX), 4 glutathione peroxidase (GPX), 3 monodehydroascorbate reductase (MDAR), 2 dehydroascorbate reductase (DHAR), 2 glutathione reductase (GR), 24 thioredoxin (Trx), and 18 glutaredoxin (GLR) genes in C. sinensis. An analysis revealed variable gene structures but conserved motifs and domains in ROS subfamilies. A comparative synteny analysis with Arabidopsis thaliana and Vitis vinifera indicated evolutionary conservation of most ROS metabolism-associated genes, with some originating from gene duplication events post-species divergence in C. sinensis. Expression profiling revealed five up-regulated genes and four down-regulated genes during both CLas and Xcc infections. Promoter analysis revealed numerous stress-responsive elements in the promoter of ROS metabolism-associated genes. Protein–protein interaction network analysis highlighted the involvement of ROS metabolism in various biological processes. A comparison of ROS metabolism-associated genes between C. sinensis and Poncirus trifoliata indicated multiple gene gain and loss events within ROS subfamilies of C. sinensis. This study enhances our understanding of ROS metabolism in C. sinensis and sheds light on citrus–pathogen interactions. [ABSTRACT FROM AUTHOR]

The sweet oranges [C. sinensis (L.) Osbeck] produced in India are mainly consumed fresh as a table fruit and in the form of freshly extracted juice. Currently, a fraction of the fruit is processed into products like orange juice, concentrates, pulp, and other value-added products. Seedless varieties are preferred both by the consumers and by the processing industry; however, indigenously developed seedless sweet orange cultivars are not available. Citrus triploids are usually seedless due to their abnormal meiosis and embryo abortion. A research study was undertaken at CCRI Nagpur to develop triploid seedless plants of the local sweet orange cultivar Mosambi through endosperm culture in the shortest possible time by dovetailing various techniques. Various steps, viz., endosperm excision, standardization of media for callus initiation, somatic embryogenesis, shoot/root differentiation, mini-grafting, and validation of the triploid status through flow cytometry, chromosome counting, and other morphological parameters, were standardized, and seven confirmed triploid plants were finally produced. An evaluation of fruit quality parameters during the 2022 and 2023 fruiting seasons revealed that the fruits of the triploid sweet orange trees were commercially seedless. This is the first reported comprehensive study on the successful development of commercially seedless plants of the sweet orange cultivar Mosambi. The fruits of the triploid plants showed desirable fruit quality parameters in terms of their seed number (3 to 5.9/fruit), higher vitamin C content (34.4 to 42.66 mg), and lower limonene content (7.77 to 11.34 µg/mL). These triploid plants have the potential to gain recognition as a distinct variety. [ABSTRACT FROM AUTHOR]

Agrometeorological models are great tools for predicting yields and improving decision-making. High-quality climatic data are essential for using these models. However, most developing countries have low-quality data with low frequency and spatial coverage. In this case, two main options are available: gathering more data in situ, which is expensive, or using gridded data, obtained from several sources. The main objective here was to evaluate the quality of two gridded climatic databases for filling gaps of real weather stations in the context of developing agrometeorological models. Therefore, a comparative analysis of gridded database and INMET data (precipitation and air temperature) was conducted using an agrometeorological model for sweet orange yield estimation. Both gridded databases had high determination and concordance coefficients for maximum and minimum temperatures. However, higher errors and lower confidence coefficients were observed for precipitation data due to their high dispersion. BR-DWGD indicated more accurate results and correlations in all scenarios evaluated in relation to NasaPower, pointing out that BR-DWGD may be better at filling gaps and providing inputs to simulate attainable yield in the Brazilian citrus belt. Nevertheless, due to the BR-DWGD database's geographical and temporal limitations, NasaPower is still an alternative in some cases. Additionally, when using NasaPower, it is recommended to use a measured precipitation source to improve prediction quality. [ABSTRACT FROM AUTHOR]

Intra-specific variation in seed storage behaviour observed in several species has been related to different maternal environments. However, the particular environmental conditions and molecular processes involved in intra-specific variation of desiccation tolerance remain unclear. We chose Citrus sinensis 'bingtangcheng' for the present study due to its known variability in desiccation tolerance amongst seed lots. Six seed lots of mature fruits were harvested across China and systematically compared for drying sensitivity. Annual sunshine hours and average temperature from December to May showed positive correlations with the level of seed survival of dehydration. Transcriptional analysis indicated significant variation in gene expression between relatively desiccation-tolerant (DT) and -sensitive (DS) seed lots after harvest. The major genes involved in late seed maturation, such as heat shock proteins, showed higher expression in the DT seed lot. Following the imposition of drying, 80% of stress-responsive genes in the DS seed lot changed to the stable levels seen in the DT seed lot prior to and post-desiccation. However, the changes in expression of stress-responsive genes in DS seeds did not improve their tolerance to desiccation. Thus, higher desiccation tolerance of Citrus sinensis 'bingtangcheng' seeds is modulated by the maternal environment (e.g., higher annual sunshine hours and seasonal temperature) during seed development and involves stable expression levels of stress-responsive genes. [ABSTRACT FROM AUTHOR]

(1) Background: The sweet orange (Citrus sinensis) is the most widely cultivated and productive citrus fruit in the world, with considerable economic value and good prospects for development. However, post-harvest storage and transport of the fruit are often affected by infestation by Penicillium species, leading to many losses. (2) Methods: In this study, the family of bZIP genes from the whole genome of sweet orange was identified and analyzed in detail in terms of gene structure, physicochemical properties, protein structure, conserved structural domains, chromosomal positioning, and promoter analysis using bioinformatic analysis, in addition to an analysis of the expression patterns of the fruit following Penicillium infection. (3) Results: In this study, 50 CsbZIP genes were identified from the sweet orange genome. In silico analysis showed that Cs_ont_3g005140 was presumably localized in the chloroplasts, while the rest of the family members were located in the nucleus. Phylogenetic trees of grape, apple, Arabidopsis, and sweet orange were constructed on the basis of evolutionary relationships and divided into 16 subfamilies. Conserved motif analysis showed that all CsbZIP family genes encode proteins containing the highly conserved Motif 1. Promoter prediction analysis showed the chromosomal positioning, and the covariance analysis showed that the 50 CsbZIPs were unevenly distributed on nine chromosomes, with 10 pairs of duplicated genes. In the analysis of expression patterns, 11 of the 50 CsbZIP genes were not expressed, 12 were upregulated, 27 were downregulated, and five of the upregulated genes were highly expressed. (4) Conclusions: In this study, two CsbZIP members were each closely related to two Arabidopsis thaliana genes associated with salt stress. The functions of the replicated and re-differentiated CsbZIP homologs (Cs_ont_1g027160 and Cs_ont_8g020880) divergee further, with one responding to inoculation by Penicillium and the other not doing so. Five genes associated with sweet orange in response to Penicillium infestation were initially screened (Cs_ont_3g000400, Cs_ont_3g003210, Cs_ont_5g007090, Cs_ont_5g011180, Cs_ont_8g020880). This study provides some theoretical basis for subsequent research into the response mechanism of sweet orange bZIP transcription factors under biotic stresses. [ABSTRACT FROM AUTHOR]

The present study evaluates the chemical compositions and antioxidant and antipathogenic properties of commercial orange (Citrus sinensis (L.) Osbeck) essential oils obtained using the cold-press method (EOP) and the cold-press method followed by steam distillation (EOPD). The chemical compositions of the volatilizable fractions, determined by gas chromatography-mass spectrometry, were similar in both samples. A relatively large amount of γ-terpinene was found in the EOPD (1.75%) as compared to the EOP (0.84%). Monoterpene hydrocarbons with limonene (90.4–89.8%) followed by myrcene (3.2–3.1%) as the main compounds comprised the principal phytochemical group. The non-volatile phenolics were eight times higher in the EOP than in the EOPD. Several assays with different specificity levels were used to study the antioxidant activity. Although both essential oils presented similar reducing capacities, the radical elimination ability was higher for the EOP. Regarding the antipathogenic properties, the EOs inhibited the biomass and cell viability of Staphylococcus aureus and Pseudomonas aeruginosa biofilms. Furthermore, both EOs similarly attenuated the production of elastase, pyocyanin, and quorum-sensing autoinducers as assessed using Gram-negative bacteria. The EOP and EOPD showed important antioxidant and antipathogenic properties, so they could represent natural alternatives to extend the shelf life of food products by preventing oxidation and contamination caused by microbial spoilage. [ABSTRACT FROM AUTHOR]

The beauty industry is actively searching for solutions to prevent skin aging. Some of the crucial elements protecting cells from the aging process are telomere shortening, telomerase expression, cell senescence, and homeostasis of the redox system. Modification of these factors using natural antioxidants is an appealing way to support healthy skin aging. Therefore, in this study, we sought to investigate the antiaging efficacy of a specific combination of four botanical extracts (pomegranate, sweet orange, Cistanche and Centella asiatica) with proven antioxidant properties. To this end, normal human dermal fibroblasts were used as a cell model and the following studies were performed: cell proliferation was established by means of the MTT assay and the intracellular ROS levels in stress-induced premature senescence fibroblasts; telomere length measurement was performed under standard cell culture conditions using qPCR and under oxidative stress conditions using a variation of the Q-FISH technique; telomerase activity was examined by means of Q-TRAP; and AGE quantification was completed by means of ELISA assay in UV-irradiated fibroblasts. As a result, the botanical blend significantly reversed the H2O2-induced decrease in cell viability and reduced H2O2-induced ROS. Additionally, the presence of the botanical ingredient reduced the telomere shortening rate in both stressed and non-stressed replicating fibroblasts, and under oxidative stress conditions, the fibroblasts presented a higher median and 20th percentile telomere length, as well as a lower percentage of short telomeres (<3 Kbp) compared with untreated fibroblasts. Furthermore, the ingredient transiently increased relative telomerase activity after 24 h and prevented the accumulation of UVR-induced glycated species. The results support the potential use of this four-component plant-based ingredient as an antiaging agent. [ABSTRACT FROM AUTHOR]

Intercropping with guava (Psidium guajava L.) can assist with the management of Asian citrus psyllid (ACP, Diaphorina citri Kuwayama), the insect vector of the huanglongbing pathogen, in citrus orchards. Sulfur volatiles have a repellent activity and physiological effects, as well as being important components of guava volatiles. In this study, we tested whether the sulfur volatiles emitted by guava plants play a role in plant–plant communications and trigger anti-herbivore activities against ACP in sweet orange plants (Citrus sinensis L. Osbeck). Real-time determination using a proton-transfer-reaction mass spectrometer (PTR-MS) showed that guava plants continuously release methanethiol, dimethyl sulfide (DMS), and dimethyl disulfide (DMDS), and the contents increased rapidly after mechanical damage. The exposure of orange plants to DMDS resulted in the suppression of the developmental performance of ACP. The differential elevation of salicylic acid (SA) levels; the expression of phenylalanine ammonia lyase (PAL), salicylate-O-methyl transferase (SMT), and pathogenesis-related (PR1) genes; the activities of defense-related enzymes PAL, polyphenol oxidase (PPO), and peroxidase (POD); and the total polyphenol content were observed in DMDS-exposed orange plants. The emission of volatiles including myrcene, nonanal, decanal, and methyl salicylate (MeSA) was increased. In addition, phenylpropanoid and flavonoid biosynthesis, and aromatic amino acid (such as phenylalanine, tyrosine, and tryptophan) metabolic pathways were induced. Altogether, our results indicated that DMDS from guava plants can activate defense responses in eavesdropping orange plants and boost their herbivore resistance to ACP, which suggests the possibility of using DMDS as a novel approach for the management of ACP in citrus orchards. [ABSTRACT FROM AUTHOR]

Citrus species, including sweet oranges, grapefruits, pomelos, and lemons, are the most widely cultivated trees and consumed fruits worldwide. In citrus orchard management, the control of Huanglongbing (HLB) disease and its insect vector Diaphorina citri (Asian citrus psyllid, ACP) represents a major global challenge. Consumers have been increasingly pushing the citrus production chain toward a more sustainable system, including stringent measures to prevent the use of chemical pesticides. In recent years, biotechnological advances have offered safe and environmentally friendly alternatives for crop production. Technologies such as RNA interference (RNAi)-mediated gene silencing have emerged as innovative tools for agricultural pest management. Here, we provide an overview of RNAi as a promising approach for ACP control and discuss the associated challenges. Despite the availability of specific silencing sequences aimed at a target gene of the insect pest, the uptake of double-stranded RNA is limited in hemipteran insects. In this context, improved delivery methods, stability maintenance, and RNAi response are considered the factors contributing to the increased effectiveness of exogenous RNAi against hemipteran pests. These approaches can serve as potential tools for efficient ACP control. [ABSTRACT FROM AUTHOR]

The role of arbuscular mycorrhizal fungi in sweet oranges is well known, but the function of their secondary metabolite, especially the easily extractable glomalin-related soil protein (EE-GRSP), an active fraction of glomalin, is still unclear. The proposed study aimed to analyze the field response of foliar application of exogenous EE-GRSP on treemycorrhizal development and fruit quality of two sweet orange (Citrus sinensis L. Osbeck) varieties viz., Lane Late Navel (LLN) and Rohde Red Valencia (RRV). Application of EE-GRSP significantly increased the root mycorrhizal colonization and soil mycorrhizal hyphal length in both the sweet orange varieties. The external quality of fruits (fruit weight, polar diameter, and equatorial diameter) also improved in response to foliar application of EE-GRSP in both sweet orange varieties. However, EE-GRSP treatment showed no change in fruit soluble solid content, while it increased the Vc content, solids-acid ratio, fructose, glucose, and sucrose content of sarcocarp in the two sweet oranges varieties. The LLN variety treated with EE-GRSP recorded significantly higher N, P, K, Fe, and Si content of sarcocarp as a mark of nutritional quality, while the RRV variety treated with EE-GRSP displayed a higher concentration of nutrients like Cu, Fe, Si, and Zn in the sarcocarp as compared with the corresponding non-treated control. To the best of our knowledge, this is the first report regarding the improvement in fruit quality of late-ripening sweet oranges (especially LLN) in response to foliar application of EE-GRSP as another potential biostimulant. [ABSTRACT FROM AUTHOR]

WRKY transcription factors (TFs) play a vital role in plant stress signal transduction and regulate the expression of various stress resistance genes. Sweet orange ( Citrus sinensis ) accounts for a large proportion of the world's citrus industry, which has high economic value, while Penicillium digitatum is a prime pathogenic causing postharvest rot of oranges. There are few reports on how CsWRKY TFs play their regulatory roles after P. digitatum infects the fruit. In this study, we performed genome-wide identification, classification, phylogenetic and conserved domain analysis of CsWRKY TFs, visualized the structure and chromosomal localization of the encoded genes, explored the expression pattern of each CsWRKY gene under P. digitatum stress by transcriptome data, and made the functional prediction of the related genes. This study provided insight into the characteristics of 47 CsWRKY TFs, which were divided into three subfamilies and eight subgroups. TFs coding genes were unevenly distributed on nine chromosomes. The visualized results of the intron-exon structure and domain are closely related to phylogeny, and widely distributed cis-regulatory elements on each gene played a global regulatory role in gene expression. The expansion of the CSWRKY TFs family was probably facilitated by twenty-one pairs of duplicated genes, and the results of Ka/Ks calculations indicated that this gene family was primarily subjected to purifying selection during evolution. Our transcriptome data showed that 95.7% of WRKY genes were involved in the transcriptional regulation of sweet orange in response to P. digitatum infection. We obtained 15 differentially expressed genes and used the reported function of AtWRKY genes as references. They may be involved in defense against P. digitatum and other pathogens, closely related to the stress responses during plant growth and development. Two interesting genes, CsWRKY2 and CsWRKY14 , were expressed more than 60 times and could be used as excellent candidate genes in sweet orange genetic improvement. This study offers a theoretical basis for the response of CSWRKY TFs to P. digitatum infection and provides a vital reference for molecular breeding.

Sweet orange (Citrus sinensis) is a sub-tropical fruit crop with important economic value that is popular worldwide; however, various pathogens significantly affect citrus cultivation and distribution. AlkB homolog (ALKBH) proteins play crucial roles in RNA metabolism and translation in plants; however, no systematic investigations have been performed on ALKBH in sweet oranges. In this study, ten ALKBH gene family members were identified in Citrus sinensis genome. Standardized analyses, including physical properties, phylogenetic analysis, gene structure, motif composition, cis-acting element prediction, chromosome distribution, and synteny analysis, were conducted. The phylogenetic analysis suggested that the ten proteins were clustered into three groups, each of which had similar motifs and gene structures. Gene expression profiling revealed that almost all CsALKBH proteins were highly expressed in callus, and ALKBH9/10-like group members responded positively to biotic stress. Overall, this study is the first to report a genome-wide assessment of the ALKBH family in sweet oranges and provides valuable insights for candidate gene selection and elucidating the molecular mechanism of sweet orange response to pathogenic infections.

The biosynthesis of sweet orange anthocyanins is triggered by several environmental factors such as low temperature. Much less is known about the effect of biotic stress on anthocyanin production in sweet orange, although in other species anthocyanins are often indicated as "defense molecules". In this work, citrus fruits were inoculated with Penicillium digitatum, the causal agent of green mold, and the amount of anthocyanins and the expression of genes related to their biosynthesis was monitored by RT-real time PCR after 3 and 5 days from inoculation (DPI). Moreover, the status of cytosine methylation of DFR and RUBY promoter regions was investigated by McrBC digestion followed in real-time. Our results highlight that fungal infection induces anthocyanin production by activating the expression of several genes in the biosynthetic pathway. The induction of gene expression is accompanied by maintenance of high levels of methylation at the DFR and RUBY promoters in the inoculated fruits, thus suggesting that DNA methylation is not a repressive mark of anthocyanin related gene expression in sweet orange subjected to biotic stress. Finally, by measuring the expression levels of the Citrus DNA demethylase genes, we found that none of them is up-regulated in response to fungal infection, this result being in accordance with the observed maintenance of high-level DFR and Ruby promoter regions methylation. [ABSTRACT FROM AUTHOR]

14-3-3 proteins (14-3-3s) are among the most important phosphorylated molecules playing crucial roles in regulating plant development and defense responses to environmental constraints. No report thus far has documented the gene family of 14-3-3s in Citrus sinensis and their roles in response to stresses. In this study, nine 14-3-3 genes, designated as CitGF14s (CitGF14a through CitGF14i) were identified from the latest C. sinensis genome. Phylogenetic analysis classified them into ε-like and non-ε groups, which were supported by gene structure analysis. The nine CitGF14s were located on five chromosomes, and none had duplication. Publicly available RNA-Seq raw data and microarray databases were mined for 14-3-3 expression profiles in different organs of citrus and in response to biotic and abiotic stresses. RT-qPCR was used for further examining spatial expression patterns of CitGF14s in citrus and their temporal expressions in one-year-old C. sinensis "Xuegan" plants after being exposed to different biotic and abiotic stresses. The nine CitGF14s were expressed in eight different organs with some isoforms displayed tissue-specific expression patterns. Six of the CitGF14s positively responded to citrus canker infection (Xanthomonas axonopodis pv. citri). The CitGF14s showed expressional divergence after phytohormone application and abiotic stress treatments, suggesting that 14-3-3 proteins are ubiquitous regulators in C. sinensis. Using the yeast two-hybrid assay, CitGF14a, b, c, d, g, and h were found to interact with CitGF14i proteins to form a heterodimer, while CitGF14i interacted with itself to form a homodimer. Further analysis of CitGF14s co-expression and potential interactors established a 14-3-3s protein interaction network. The established network identified 14-3-3 genes and several candidate clients which may play an important role in developmental regulation and stress responses in this important fruit crop. This is the first study of 14-3-3s in citrus, and the established network may help further investigation of the roles of 14-3-3s in response to abiotic and biotic constraints. [ABSTRACT FROM AUTHOR]

Among the many approaches to Coronavirus disease 2019 (COVID-19) prevention, the possible role of nutrition has so far been rather underestimated. Foods are very rich in substances, with a potential beneficial effect on health, and some of these could have an antiviral action or be important in modulating the immune system and in defending cells from the oxidative stress associated with infection. This short review draws the attention on some components of citrus fruits, and especially of the orange (Citrus sinensis), well known for its vitamin and flavonoid content. Among the flavonoids, hesperidin has recently attracted the attention of researchers, because it binds to the key proteins of the Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Several computational methods, independently applied by different researchers, showed that hesperidin has a low binding energy, both with the coronavirus "spike" protein, and with the main protease that transforms the early proteins of the virus (pp1a and ppa1b) into the complex responsible for viral replication. The binding energy of hesperidin to these important components is lower than that of lopinavir, ritonavir, and indinavir, suggesting that it could perform an effective antiviral action. Furthermore, both hesperidin and ascorbic acid counteract the cell damaging effects of the oxygen free radicals triggered by virus infection and inflammation. There is discussion about the preventive efficacy of vitamin C, at the dose achievable by the diet, but recent reviews suggest that this substance can be useful in the case of strong immune system burden caused by viral disease. Computational methods and laboratory studies support the need to undertake apposite preclinical, epidemiological, and experimental studies on the potential benefits of citrus fruit components for the prevention of infectious diseases, including COVID-19. [ABSTRACT FROM AUTHOR]

Mature 'Hamlin' sweet oranges (Citrus sinensis (L.) Osbeck) were irradiated using light-emitting diodes (LEDs) and ultraviolet (UV) light for six days after harvest. Based on evaluation of the basic ripening parameters of fruits, the contents of soluble sugars, organic acids, and carotenoids were analyzed (in pulps) on the sixth day by high-performance liquid chromatography (HPLC). The results showed that LED and UV irradiation not only accelerated orange ripening but also caused significant changes in the soluble sugar, organic acid, and carotenoid content. Compared with fruit subjected to dark shade (DS) treatment, the total soluble sugar, fructose, and glucose contents increased significantly in UV-treated (UVA, UVB, and UVC) fruits, while the sucrose content increased remarkably in white light, UVB, and UVC-treated fruits (p < 0.05). UV treatment was associated with inducing the largest effect on the total soluble sugar content. Except for UVB, other types of light notably induced an accumulation of the total organic acid content, none but blue light and red light markedly induced citric acid accumulation (p < 0.05). Interestingly, only the red light and dark shade treatments had markedly positive effects in terms of inducing carotenoid accumulation, including the total carotenoid, isolutein, zeaxanthin, lutein, neoxanthin, all-trans-violaxanthin, phytofluene, cis-ζ-carotene, and β-carotene concentrations. Other light treatments had significantly negative effects on carotenoid accumulation (p < 0.05). Therefore, soluble sugar, organic acid, and carotenoid accumulation in sweet oranges vary depending on the levels of UV and LED irradiation. Appropriate light irradiation is a potentially effective way to maintain or improve postharvest fruit quality. [ABSTRACT FROM AUTHOR]

Citrus fruits have been a commercially important crop for thousands of years. In addition, Citrus essential oils are valuable in the perfume, food, and beverage industries, and have also enjoyed use as aromatherapy and medicinal agents. This review summarizes the important biological activities and safety considerations of the essential oils of sweet orange (Citrus sinensis), bitter orange (Citrus aurantium), neroli (Citrus aurantium), orange petitgrain (Citrus aurantium), mandarin (Citrus reticulata), lemon (Citrus limon), lime (Citrus aurantifolia), grapefruit (Citrus × paradisi), bergamot (Citrus bergamia), Yuzu (Citrus junos), and kumquat (Citrus japonica). [ABSTRACT FROM AUTHOR]