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• We first report a new pathway model, including the Ca2+/CaM pathway, the ROS pathway, and the ABA pathway, for the response of the Hsf gene family in sweet orange to abiotic and biotic stresses. • Heat shock transcription factors family were identified for the first time in sweet orange, all with typical DBD and HR-A/B structural domains. • A total of 17 CsHsf genes were identified in sweet orange. • Phylogenetic analyses showed close affinity to Citrus clementina, CsHsf can be divided into three families and 14 subfamilies, gene structure, and protein motif analyses supported the results of phylogenetic analyses. Sweet orange (Citrus sinensis) is the most widely planted and productive citrus fruit, but its growth and yield are susceptible to abiotic and biotic stresses. Heat shock transcription factors (Hsfs) play important roles in regulating plant growth and development and resistance to pests and diseases. However, a systematic study of the CsHsf gene family has not been reported. In this study, we used bioinformatics methods to identify the genome-wide Hsf gene family in sweet orange and then systematically analyzed its gene features, subcellular localization, phylogeny, promoter cis-acting elements, protein interactions, and expression profiles. Seventeen CsHsf gene family members were identified; these genes were randomly distributed on eight chromosomes, and most of the CsHsfs were located in the nucleus. Phylogenetic analyses revealed that CsHsf is closely related to Citrus clementina , and CsHsf can be divided into three clades and 14 subclades. Gene subclades structure and motif analyses supported the results of phylogenetic analyses, and most of the promoter regions of CsHsf gene family members contained cis-responsive elements related to adverse stresses, hormones, and growth and development. GO analyses indicated that the CsHsf gene family plays a role in resistance to environmental stresses and the regulation of metabolism, and the 3D structure revealed a conserved CsHsf protein structure. RNA-Seq data analysis suggested that the CsHsf4 gene has an anti- Penicillium digitatum function. In addition, we first report a new pathway model, including the Ca2+/CaM pathway, the ROS pathway, and the ABA pathway, for the response of the Hsf gene family in sweet orange to abiotic and biotic stresses. This study lays a foundation for abiotic and biotic stress-resistance gene selection and disease-resistance breeding in sweet orange. [ABSTRACT FROM AUTHOR]

Day-by-day increasing irrigation water scarcity requires the application of water-saving irrigation techniques to sustain agriculture production. A two-year field investigation was conducted during 2018 to 2020 to determine the effects of various mulches and irrigation volumes on the growth, leaf chemicals and soil properties of one-year-old sweet oranges (Citrus sinensis) cv. Mosambi. The study included three irrigation schedules, viz.100% ETc (I1), 80% ETc (I2), and 60% ETc (I3), and five different mulches were used, viz. without mulch, white polythene, coriander straw, dry grass and black polythene mulches, replicated thrice. Results demonstrated that drip irrigation with 100% ETc and mulching with black polythene mulch significantly increase the plant growth attributes like height of the plant (28.64%) (30.31%), rootstock girth (36.61%) (37.90%), plant canopy spread (E-W and N-S) (EW- 63.82%, NS- 63.87%) (EW- 67.56%, NS- 67.90%) and leaf area (2.4%) (2.34%). Furthermore, plant leaf chlorophyll content (2.41 mg g-1) (2.41 mg g-1) and leaf mineral content such as N (2.39%) (2.40%), P (0.16%) (0.165%), K (1.57%) (1.59%), Ca (47.34 g kg-1) (47.80 g kg-1), Mg (4.54 g kg-1) (4.57 g kg-1), Fe (120.51 g kg-1) (123.15 g kg-1) and Zn (39.00 g kg-1) (37.84 g kg-1) were noted to be significantly (p ≤ 0.05) higher in plants that received 100% (were ETc (I1) and mulching with black polythene mulch (M1) treatment. Taken together, the results suggested that treatments I1 and M1 have the potential to maximize plant growth, leaf chemicals and soil nutrients of sweet orange (Citrus sinensis) cv. Mosambi plants. [ABSTRACT FROM AUTHOR]

Introduction: Reactive oxygen species (ROS) generation is a common disease defense mechanism in plants. However, it is unclear whether Citrus host activates defense response against Diaporthe citri causing citrus melanose disease by producing ROS, and the underlying molecular mechanisms are unknown. Methods: DAB staining and RNA-Seq technology were used to compare the active oxygen burst and differential gene expression, respectively, in uninfected and infected Citrus sinensis leaves at different time points during D. citri infection in vivo. The functions of CsRBOH (a significant DEG) were confirmed in N. benthamiana through the Agrobacterium-mediated transient expression system. Results: DAB staining indicated that C. sinensis initiated defense against D. citri infection within 24 h by generating ROS. Illumina sequencing revealed 25,557 expressed genes of C. sinensis. The most upregulated DEGs (n = 1,570) were identified 72 h after fungal inoculation (sample denoted as CD72). In the CD72 vs. Cs (samples at 0 h after fungal inoculation) comparison, the KEGG pathway category with the highest number of genes (n = 62) and most significant enrichment was Protein processing in endoplasmic reticulum, followed by Glutathione metabolism and MAPK signaling pathway-plant. GO analysis revealed that the DEGs of CD72 vs. Cs related to active oxygen burst and chitin recognition were significantly grouped into the regulation of biological processes and molecular functions, with GO terms including response to ROS, response to fungus, and oxidoreductase activity. Remarkably, CsRBOH was significantly enriched in the GO and KEGG analyses, and its expression pattern in qRT-PCR and DAB staining results were consistent. Among the 63 ROS-related DEGs, HSP genes and genes associated with the peroxidase family were highly significant as revealed by protein–protein interaction networks. Furthermore, ROS accumulation, cell death, and upregulation of defense-related genes were observed in N. benthamiana leaves with CsRBOH expressed through the Agrobacterium-mediated transient expression system. Conclusion: Our findings suggested that C. sinensis activates CsRBOH and ROSrelated genes, leading to ROS accumulation to resist the invasion by D. citri. This study laid the foundation for future research on molecular mechanisms and breeding of C. sinensis cultivars resistant to citrus melanose. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to examine the effect of aromatherapy with an essential oil blend containing lavender, bergamot, ylangylang, and sweet orange, compared with placebo, on perceptions of anxiety in ICU RNs. Methods: Nurses recruited from six adult ICUs and a neonatal ICU participated in this blinded, randomized, placebo-controlled study, which took place over a 30-day intervention period. Results: Although there were no statistically significant changes in anxiety pre- to postintervention or between the intervention and placebo groups, there were also no adverse events or untoward effects. Conclusion: The results of this study may support aromatherapy as an evidence-based strategy to reduce anxiety in ICU nurses. Additional research is needed. [ABSTRACT FROM AUTHOR]

Impact of integrated nutrient management on plant and soil nutrient status in sweet orange (Citrus sinensis L.) cv. Phule Mosambi was investigated for two consecutive years i.e. 2019 and 2020 at the Horticultural Research Farm, College of Horticulture, Anand Agricultural University, Anand. The experiment was laid out in completely randomized design (CRD) comprised of 11 treatments replicated thrice. Significantly higher yield was recorded with T11 [50% Recommended Dose of Nitrogen (RDN) + 20 kg farmyard manure (FYM)/tree +25% nitrogen (N) from Castor Cake + 10 ml Bio NPK Consortium + Micronutrient foliar spray (1% Grade IV)] (17.35 and 17.01 t/ha) which was at par with T10 (15.92 and 15.56 a t/ha) during 2019 and 2020, respectively. Amongst the treatments, T11 had increased the nutrient contents of soil as well as in plant and recorded maximum available nitrogen (N), available potassium (K), soil boron (B) content, plant nitrogen (N) content, plant iron (Fe) content, plant copper (Cu) content and plant boron (B) content in both the years whereas available phosphorous (P) was found higher in treatment T7 in both the years. Treatment T8 recorded highest soil copper (Cu) content in both the years. As far as plant zinc (Zn) content is concerned, it was found higher in treatment T9 in both the years. [ABSTRACT FROM AUTHOR]

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]

BACKGROUND: Xylella fastidiosa is a multi‐host bacterium that can be detected in hundreds of plant species including several crops. Diseases caused by X. fastidiosa are considered a threat to global food production. The primary method for managing diseases caused by X. fastidiosa involves using insecticides to control the vector. Hence, it is necessary to adopt new and sustainable disease management technologies to control not only the insect but also the bacteria and plant health. We demonstrated that N‐acetylcysteine (NAC), a low‐cost cysteine analogue, is a sustainable molecule that can be used in agriculture to decrease the damage caused by X. fastidiosa and improve plant health. RESULTS: Using 15N‐NAC we proved that this analogue was absorbed by the roots and transported to different parts of the plant. Inside the plant, NAC reduced the bacterial population by 60‐fold and the number of xylem vessels blocked by bacterial biofilms. This reflected in a recovery of 0.28‐fold of the daily sap flow compared to health plants. In addition, NAC‐treated citrus variegated chlorosis (CVC) plants decreased the oxidative stress by improving the activity of detoxifying enzymes. Moreover, the use of NAC in field conditions positively contributed to the increase in fruit yield of CVC‐diseased plants. CONCLUSION: Our research not only advances the understanding of NAC absorption in plants, but also indicates its dual effect as an antimicrobial and antioxidant molecule. This, in turn, negatively affects bacterial survival while improving plant health by decreasing oxidative stress. Overall, the positive field‐based evidence supports the viability of NAC as a sustainable agricultural application. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Abstract Day-by-day increasing irrigation water scarcity requires the application of water-saving irrigation techniques to sustain agriculture production. A two-year field investigation was conducted during 2018 to 2020 to determine the effects of various mulches and irrigation volumes on the growth, leaf chemicals and soil properties of one-year-old sweet oranges (Citrus sinensis) cv. Mosambi. The study included three irrigation schedules, viz.100% ETc (I1), 80% ETc (I2), and 60% ETc (I3), and five different mulches were used, viz. without mulch, white polythene, coriander straw, dry grass and black polythene mulches, replicated thrice. Results demonstrated that drip irrigation with 100% ETc and mulching with black polythene mulch significantly increase the plant growth attributes like height of the plant (28.64%) (30.31%), rootstock girth (36.61%) (37.90%), plant canopy spread (E-W and N-S) (EW- 63.82%, NS- 63.87%) (EW- 67.56%, NS- 67.90%) and leaf area (2.4%) (2.34%). Furthermore, plant leaf chlorophyll content (2.41 mg g-1) (2.41 mg g-1) and leaf mineral content such as N (2.39%) (2.40%), P (0.16%) (0.165%), K (1.57%) (1.59%), Ca (47.34 g kg-1) (47.80 g kg-1), Mg (4.54 g kg-1) (4.57 g kg-1), Fe (120.51 g kg-1) (123.15 g kg-1) and Zn (39.00 g kg-1) (37.84 g kg-1) were noted to be significantly (p ≤ 0.05) higher in plants that received 100% (were ETc (I1) and mulching with black polythene mulch (M1) treatment. Taken together, the results suggested that treatments I1 and M1 have the potential to maximize plant growth, leaf chemicals and soil nutrients of sweet orange (Citrus sinensis) cv. Mosambi plants.

Superoxide dismutase (SOD) protects plants from biotic and abiotic stress-induced reactive oxygen species toxicity and is extensively involved in plant growth and development. As the most widely cultivated and productive citrus fruit in the world, sweet oranges are susceptible to biotic and abiotic stresses during growth, affecting their yield and quality. However, the SOD gene family has not been identified in sweet oranges. Therefore, in this study, the sweet orange SOD gene family was systematically identified using bioinformatics methods, and a total of 15 sweet orange SOD (CsSOD) genes were identified and categorized into three subfamilies, Cu/Zn–SOD, Fe–SOD, and Mn–SOD, based on the results of the phylogenetic tree. Further analysis of gene structure and conserved motifs revealed that the motifs and exon and intron structures of CsSOD genes in the same subfamily were relatively identical, with only minor differences. In addition, we predicted hormone-related, light-response-related, and defense-related cis-acting elements in the promoters 2 kb upstream of the CsSOD genes. Transcriptome data analysis revealed that SOD genes were expressed under both abiotic and abiotic stresses, and the expression levels of some of the genes varied significantly. This study provides a basis for further understanding the biologic properties and functions of the SOD gene family in sweet oranges and provides a vital foundation for the study of sweet oranges under biotic and abiotic stresses. [ABSTRACT FROM AUTHOR]

Introduction: The leaves of Plectranthus amboinicus (Lour.) Spreng, commonly known as French oregano, are traditionally used for their action as an anti-asthmatic, expectorant, bronchodilator and antimicrobial, while the bark of Citrus sinensis L. is used as an antiinflammatory, antitussive and expectorant. Objective: To verify specifications for quality control of herbal active ingredients obtained from P. amboinicus and C. sinensis powder. Materials and Methods: In this study, the quality control of ten lots supplied by the laboratories of different municipalities in the province of Villa Clara was carried out, applying tests described in pharmacopoeias BP (2020), UPS (2017) and in the national formulary. Results and Discussion: The results revealed that the loss on drying should not exceed 11%, while the total ashes should not be greater than 20 and 7% and the ashes insoluble in hydrochloric acid should not exceed 8 and 2% for oregano and peel orange, respectively. Thin layer demonstrated the presence of carvacrol in French oregano and quercetin and hesperidin in orange peel. The leaves of Plectranthus amboinicus contain not less than 0.7% carvacrol and the peel of Citrus sinensis contains not less than 0.2% flavonoids; these metabolites provide the pharmacological actions for which both plants are used in Cuban traditional medicine. Conclusions: Both raw materials have adequate quality by complying with the quality specification limits of the tests evaluated in this work. [ABSTRACT FROM AUTHOR]

Background: Sweet oranges are a vital agricultural commodity, but they are susceptible to various pathogenic fungi that can cause significant economic losses. This study aimed to evaluate the antifungal activity of plant extracts against pathogenic fungi attacking sweet oranges in Jimma, Ethiopia. Materials and methods: Various plant extracts were obtained from locally available plant species and tested against selected pathogenic fungi using standard in vitro antifungal assays. The results revealed varying degrees of antifungal activity among the plant extracts, with some showing promising inhibitory effects against the targeted fungi. Statistical analysis indicated significant differences in antifungal efficacy among the tested extracts. Results: The study found that Penicilium spp., Aspergillus spp., Rhizopus spp., Mucor spp., and Fusarium spp, were the predominant fungal species. The study found that the extracts of Vernonia amygdalina, Ginger oficealae, and Pterolobium stalatam were effective in inhibiting mycelial growth against these pathogens. This suggests the use of these medicinal plants for the preservation and control of sweet orange fruit in most of the Ethiopian region. Conlusion: These findings suggest the potential of certain plant extracts as natural alternatives to synthetic fungicides for managing fungal diseases in sweet orange cultivation. Further research is needed to elucidate the mechanisms of action of these plant extracts and optimize their application in agricultural practices. This study contributes to the development of sustainable and eco-friendly strategies for plant disease management in the region.Article Highlights: The researchers identified various plant extracts that exhibit significant antifungal properties against fungi. The study conducted a comparative analysis between natural plant extracts and conventional chemical fungicides. Detailed phytochemical analysis identified the active compounds for the antifungal activity. [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]

Rootstock as grafting material mitigates sodium chloride (NaCl) stress by altering physiological, metabolite, and gene expression patterns across different genotypes, cultivars, or species. In this study, we investigated the antioxidant and metabolic responses of sweet orange cultivar Pusa Sharad (PS) grafted onto various rootstocks: Jatti Khatti (JK), X–639 (X9), CRH–12 (C12), NRCC–1 (N1), NRCC–2 (N2), NRCC–3 (N3), NRCC–4 (N4), NRCC–5 (N5), Troyer citrange (TC), CRH–47 (C47), and Cleopatra mandarin (CM). These responses were assessed under different salinity stress levels. Biochemical parameters, including sugars, proline, phenol, soluble protein, hydrogen peroxide (H2O2), superoxide radicals (O2–), lipid peroxidation, catalase (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR), peroxidase (POD), vitamin C, vitamin E, organic acids, and fatty acids were analysed. Results demonstrated that the accumulation of H2O2, O2–, and malondialdehyde (MDA) was upregulated in PS grafted onto the TC, JK, N2, and C12 rootstocks. Conversely, the CAT, SOD, APX, vitamin C, and vitamin E contents were notably higher in PS grafted onto CM, X9, and C47 under 60 mM NaCl stress. Metabolomic analysis indicated that trehalose, raffinose, sucrose, D-galactose, myo-inositol, piperazine, acetic acid, malonic acid, palmitic acid, stearic acid, and pentanoic acid played crucial roles in metabolic adjustments under increasing NaCl stress. Furthermore, PS grafted onto CM, C47, X9, N1, or N3 showed greater tolerance to NaCl compared to those grafted onto JK, C12, N2, N4, N5, or TC, making these combinations adaptable upto 60 mM NaCl concentrations. This study highlights the role of potential metabolites and its use in enhancing NaCl tolerance through grafting onto tolerant rootstocks.

Callose is a 1,3-β glucan responsible for several processes in planta such as cell division, ripening of pollen mother cells, maintaining the plasmodesmata opening, and providing structure to the sieve plates. Besides the physiological roles, callose is deposited during pathogen attacks, forming papillae to prevent pathogen entrance into the tissue or plugging the sieve pores to limit the spread of phloem pathogens. Candidatus Liberibacter asiaticus (CLas), the putative causal agent of Huanglongbing (HLB), is a phloem-restricted pathogen whose infection leads to the production of callose in the phloem. Characterizing the dynamics of callose plugging during HLB is important for understanding the disease, but no published protocols are available for the extraction and quantification of the callose in citrus trees, and quantitative data are limited. Detection of callose by microscopy is time-consuming and expensive and does not give information about the distribution of callose in the entire plant. Here, we present a short protocol for the efficient extraction and quantification of the total callose from citrus plants. We compared different tissues from healthy and CLasinfected plants and identified an increase in callose levels in the midribs, the stems, and the fruit peduncles of infected plants. Callose levels were highest in leaves, especially midribs, compared to stems, roots, and fruit peduncles. This method could be applied to other woody plant species. [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]

Background and aims: Zinc (Zn) deficiency is widespread in citrus orchard around the world, which impairs plant growth and fruit yield. Zn fertilization is usually recommended in field orchards, and application strategies toward nutrient use efficiency are key for successful crop management. Methods: Field studies were carried out with sweet orange trees for four growing seasons, testing Zn (nitrate, sulfate or EDTA) applied either via fertigation or foliar spray compared to a control without Zn. Results: The Zn concentrations in the soil increased with nutrient supply by both application methods. Zn-EDTA via fertigation increased soil nutrient availability compared to the control. Likewise, Zn-nitrate via foliar application also increased soil Zn levels. Regarding the plant, Zn-EDTA via fertigation increased leaf nutrient levels only after the third year of fertilization, whereas Zn-nitrate via foliar spray increased leaf levels in the short term, up to 120 mg kg−1. To a lesser extent, Zn-EDTA or sulfate also increased leaf Zn compared to the control. Accumulated fruit yield was ~20% higher in trees with Zn-EDTA via fertigation and ~ 20% higher in trees with Zn-nitrate or sulfate via foliar application compared to the control, with these latter exerting greater responses. Trees supplied with Zn exhibited lower H2O2 and higher CAT activity compared to the control, which correlated with a fruit yield increase. Conclusion: In conclusion, Zn-EDTA via fertigation or nitrate or sulfate via foliar application improved the horticultural performance of trees, supporting the establishment of best nutrient management practices in fruit production. [ABSTRACT FROM AUTHOR]

Abstract: Nitrogen (N) fertilization in citrus orchards is prone to significant environmental losses. Managing nutrients for sustainable development and optimizing nitrogen use efficiency (NUE) are key tasks in modern agriculture. NUE depends on N uptake and assimilation. In addition to intrinsic fertilizer use efficiency, we evaluated plant growth, nitrate reductase (NRase) activity, and the nutritional status of citrus plants fertilized with different N sources [calcium nitrate (CN), ammonium nitrate (AN), and ammonium sulfate (AS)]. After 240 days, plants supplied with either CN or AN exhibited higher biomass production and N accumulation in the leaves than those fertilized with AS. The supply of ammonium-containing sources (AN and AS) reduced the substrate pH, in which those with AS exhibited lower N partitioning to the leaves, as well as reduced the absorption and accumulation of magnesium and phosphorus. NRase activity was higher in plants supplied with CN or AN compared to AS, and CN fertilization provided the greatest NUE. The data demonstrated that citrus plants fertilized with sources containing nitrate increased the NUE from 10 to 25% and consequently had greater growth compared to those fed with AS.

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.

We report the effects of orange oil encapsulation on the properties of PCL/Pluronic F68-based nanoparticles obtained by the nanoprecipitation technique. Orange oil is a potential candidate as a bioactive compound for the treatment of chronic diseases due to its antioxidant and anti-inflammatory properties. However, this essential oil is poorly soluble and highly volatile. An approach to enhance its solubility while maintaining its properties is nanoencapsulation. To this end, we prepared by the nanoprecipitation method PCL-based nanoparticles coated with Pluronic F68 and loading different concentrations of orange oil–5, 10, 15, and 20%. We characterized the nanosystems by dynamic light scattering, zeta-potential measurement, Fourier-transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, retention efficiency, relaxometry, antioxidant capacity, and release profile techniques. All formulations had monodispersed distributions and nanometric diameters. Besides, the orange oil exhibited a stabilizing and cryoprotective effect on the colloidal dispersions. The infrared spectroscopy analysis revealed the existence of only physical interactions between the oil and the applied matrices. The oil retention volume was higher than 69%, and its encapsulation sustained the active principle's release for approximately 7 h. Moreover, it was possible to observe the presence of the oil in both polymeric layers of nanoparticles and the maintenance of its antioxidant activity. Therefore, the nanoencapsulation of orange oil by colloidal carriers is of interest for its therapeutic potential and its stabilizing action on colloidal carriers. [ABSTRACT FROM AUTHOR]

Research background. There is considerable diversity in newly developed pummelo x sweet orange citrus hybrids. Most hybrids showed lower peel thickness and high juice yield but there is a lack of information on fruit quality parameters and molecular characterization. Therefore, the aim of the current study is to determine the content of antioxidants and properties of the fresh juice of 24 new pummelo x sweet orange citrus hybrids (Citrus maxima [Burm. f.] Osbeck x Citrus sinensis [L.] Osbeck) and the parental genotypes along with molecular characteristics determined using acidity specific markers. Experimental approach. The correlation and estimate of inheritance of the fruit juice properties: ascorbic acid, total phenol, total flavonoid, total antioxidant, total soluble solid and sugar contents, pH, titratable acidity, along with sensory evaluation was performed. Molecular characterization of these hybrids was carried out using de novo generated acidity specific simple sequence repeat (SSR) markers. Results and conclusions. The main constituents of the fruit juice of pummelo x sweet orange hybrids were observed in the range of w(ascorbic acid)=40.00-58.13 mg/100 g, total phenols expressed as gallic acid equivalents w(GAE)=40.67-107.33 mg/100 g, total antioxidants expressed as Trolox equivalents b(Trolox)=2.03-5.49 μmol/g, total flavonoids expressed as quercetin equivalents w(QE)=23.67-59.33 mg/100 g, along with other properties: total soluble solids=7.33-11.33 %, w(total sugar)=2.10-5.76 %, w(reducing sugar)= 1.69-2.78 %, w(non-reducing sugar)=0.39-3.17 % and titratable acidity 1.00-2.11 %. The above parameters differed significantly in the fruit juice of the evaluated pummelo x sweet orange hybrids. Considering these parameters, the hybrids SCSH 17-9, SCSH 13-13, SCSH 11-15 and SCSH 3-15 had superior antioxidant properties in terms of these parameters. A higher heritability (≤80 %) was also observed for all juice properties. Molecular characterization of pummelo x sweet orange hybrids showed that >50 % of the hybrids were grouped with medium acidity parents. Both molecular and biochemical parameter-based clustering showed that interspecific hybrids exhibit transgressive segregation with increased antioxidants that help alleviate the health problems. Novelty and scientific contribution. These newly developed pummelo x sweet orange citrus hybrids are a valuable source of high-quality antioxidants for a healthy diet. The identification of trait markers that enable selection at the seedling stage is of great benefit to citrus breeders, as the characteristic features of a mature tree are not yet visible at the juvenile stage. [ABSTRACT FROM AUTHOR]

AbstractPlant-based derivatives (powders, pellets or extracts) are amongst the most effective types of organic soil amendments for the management of root-knot nematodes (Meloidogyne spp.). The objective of this study was to examine the effect of derivatives (juice, powder and oil) of fruits of several Citrus species (sweet orange, lemon, lime, mandarin and grapefruit) on the reproduction of Meloidogyne incognita race 2 on susceptible tomato plants, and on the vegetative growth of the crop under glasshouse conditions. Results show that juices of sweet orange, and possibly also lemon, applied as soil amendments either before planting or after planting, can significantly suppress the build-up of damaging root population densities of M. incognita on infected tomato plants, limit root galling and improve plant growth. Data confirm the nematode-suppressive and plant-growth enhancing effects reported for Citrus fruit-based plant derivatives, applied either as a compost, powder, extract or pellet. [ABSTRACT FROM AUTHOR]

For over two decades, Florida citrus growers have been heavily using copper sprays to combat citrus canker (Xanthomonas citri subsp. citri; Xcc), but it raises the risk of developing resistant bacterial strains and excessive accumulation in the soil. Alternative methods are needed to reduce copper dependency and better manage Xcc. Therefore, we screened copper-alternative products against canker on young seedlings in the greenhouse and mature trees in a commercial grove in Florida, USA. In the greenhouse, we evaluated the efficacy of single foliar application of new plant defense inducers (PDI), 'PDI5', 'PDI26', and 'PDI31', and a commercially available systemic acquired resistance inducer, Actigard (drench; 2g/tree), applied two days before injection-infiltration with citrus canker bacterium Xcc (104 CFU/ml), on two-year-old Valencia trees. All three PDIs, sprayed at 500 ppm, as well as Actigard (drench), effectively reduced canker severity on the inoculated leaves in the greenhouse (P =0.02). In the grove, we tested new antimicrobials, Mastercop 'MC' (21.46% copper sulfate pentahydrate; metallic copper equivalent 5.4%) at concentrations of 1.12 kg/ha, 1.68 kg/ha and 2.24 kg/ha, 'AM' at 1.68 kg/ha and 2.24 kg/ha, and a nutrient solution (AGROMOS) at 1.12 kg/ha for canker suppression on 4-6-year-old Hamlin trees. Kocide 2000 (growers' standard control; metallic copper equivalent 30%; 3.92 kg/ha) was used as a control check. Although 2021 was not as conducive for citrus canker due to the relatively dry spring months in the field, our results showed that the six sprays of AM (2.24 kg/ha) or MC (1.68 kg/ha, and 2.24 kg/ha), in 2022, provided excellent control of Xcc, with a significant reduction in disease incidence in leaves and fruits, and disease severity in fruits, similar to Kocide 2000. The results indicate that antimicrobials, AM and MC, and plant defense inducers PDI5, PDI26, and PDI31 can be part of an integrated pest management (IPM) program with copper for managing citrus canker. Reducing the frequency and amount of copper applications can help reduce pesticide and application expenses, lower risks of copper buildup in the soil and toxicity for citrus trees and reduce the risk of the emergence of copper-resistant Xcc strains. Further research on these products is needed to assess their long-term effectiveness and potential environmental risks. [ABSTRACT FROM AUTHOR]

Callose is a 1,3-β glucan responsible for several processes in planta such as cell division, ripening of pollen mother cells, maintaining the plasmodesmata opening, and providing structure to the sieve plates. Besides the physiological roles, callose is deposited during pathogen attacks, forming papillae to prevent pathogen entrance into the tissue or plugging the sieve pores to limit the spread of phloem pathogens. Candidatus Liberibacter asiaticus (CLas), the putative causal agent of Huanglongbing (HLB), is a phloem-restricted pathogen whose infection leads to the production of callose in the phloem. Characterizing the dynamics of callose plugging during HLB is important for understanding the disease, but no published protocols are available for the extraction and quantification of the callose in citrus trees, and quantitative data are limited. Detection of callose by microscopy is time-consuming and expensive and does not give information about the distribution of callose in the entire plant. Here, we present a short protocol for the efficient extraction and quantification of the total callose from citrus plants. We compared different tissues from healthy and CLas-infected plants and identified an increase in callose levels in the midribs, the stems, and the fruit peduncles of infected plants. Callose levels were highest in leaves, especially midribs, compared to stems, roots, and fruit peduncles. This method could be applied to other woody plant species.

An analgesic-antipyretic drug widely used is paracetamol, which has various health benefits and several adverse effects. Therefore, various natural products have been extensively studied as alternative analgesic-antipyretics, one of which is sweet orange peel. This study aimed to investigate sweet orange peel's analgesic and antipyretic activity by in vivo methods. This experimental study evaluated the analgesic and antipyretic effects of sweet orange peel extract extracted by the maceration method. The analgesic effect was evaluated by tail immersion (Maximum Possible Analgesia) and acetic acid-induced writhing method (total abdominal writhing). Meanwhile, the antipyretic effect was evaluated by the brewer yeast-induced hyperpyrexia (body temperature) method. This study showed that sweet orange peel methanol extract significantly increased the maximum possible analgesia value (132.79%) and reduced the number of abdominal writhing (44.05%) at the highest dose of 750 mg/kg BW. It indicated analgesic activity from sweet orange peels. Meanwhile, the antipyretic effect of sweet orange peel methanol extract was observed from 1-4 hours after administration, and the highest percentage inhibition of body temperature 4 hours after administration was found in a moderate dose, that was 5.98% (P value: 0.042). Therefore, it can be concluded that sweet orange peel methanol extract has analgesic and antipyretic effects with an optimal dose range of 500-750 mg/kg BW.

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.

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 Centromeres play a crucial role in ensuring the accurate separation of chromosomes during cell division. Despite the three rounds of genome sequencing technology undergone by Citrus sinensis (sweet orange), the presence of numerous repetitive DNA elements in its genome has led to substantial gaps in centromeric genomic mapping, leaving the composition of centromeric repeats unclear. To address this, we employed a combination of chromatin immunoprecipitation sequencing with the C. sinensis centromere-specific histone H3 variant antibody and centromere-specific bacterial artificial chromosome-3a sequencing to precisely locate the centromeres. This approach allowed us to identify a series of centromere-specific repeats, comprising five tandem repeats and nine long terminal repeat retrotransposons. Through comprehensive bioinformatics analysis, we gained valuable insights into potential centromeric evolution events and discovered the presence of DNA G-quadruplex structures of centromeric repeats in C. sinensis. Altogether, our study not only offers a valuable reference for centromeric genome assembly but also sheds light on the structural characteristics of C. sinensis centromeres.

Insect pollination plays a pivotal role in maintaining sustainable and profitable agriculture practices with limited environmental disturbance. This research was conducted to assess the diversity of floral visitor insects and their foraging and behavioral activities over two seasons. In addition, we determined the impact of insect pollination on the qualitative and quantitative parameters of sweet orange (cvs. Early Gold, Rhode Red, and Trovita). During seasons 1 and 2, seven insect species, including six Hymenopterans and one Dipteran, visited the sweet orange flowers and collected nectar and/or pollen. During the two seasons, the highest mean number of flowers visited (per min) by various floral visitor insects was recorded for Xylocopa tenuiscapa Westwood and the lowest for Nomia sp. The time spent (s/flower) was the highest in Nomia sp. and lowest in X. tenuiscapa. The fruit set, fruit yield, fruit weight, number of seeds/fruit, and total soluble solids (TSS) content were considerably higher with open pollination during the two seasons than with pollinator exclusion. In both seasons the highest fruit set, number of seeds/fruit, fruit weight, and fruit yield were noted in cv. Early Gold. To summarize, the quality and quantity of fruit production of sweet oranges were influenced by insect pollination. [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.

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.

The use of canopy density for crop production is a useful tool for evaluating management practices for informed decision-making and predicting crop yields. Traditional methods for analyzing canopy density include expensive equipment that requires advanced software and costly repairs, such as leaf area index analyzers, or equipment that can only be used during optimal weather conditions, such as light meters, that quantify photosynthetically active radiation (PAR), thus making it difficult for researchers to maximize the time needed for field research evaluations and data collection. Digital image analyses using technologically advanced cameras, such as smartphone cameras, have allowed new ways of collecting data without the need to purchase specialized instruments. Using a combination of smartphone cameras and ImageJ software, canopy density can be measured in any weather conditions for a much lower cost than that of traditional equipment. This low-cost, digital image analysis method was compared with traditional PAR measurements for ‘Valencia’ sweet orange [Citrus sinensis (L.) Osb.] trees with varying levels of canopy density. A strong positive correlation between the digital image analysis method and standard canopy density measurement method using PAR measurements (r = 0.79; P

For over two decades, Florida citrus growers have been heavily using copper sprays to combat citrus canker (Xanthomonas citri subsp. citri; Xcc), but it raises the risk of developing resistant bacterial strains and excessive accumulation in the soil. Alternative methods are needed to reduce copper dependency and better manage Xcc. Therefore, we screened copper-alternative products against canker on young seedlings in the greenhouse and mature trees in a commercial grove in Florida, USA. In the greenhouse, we evaluated the efficacy of single foliar application of new plant defense inducers (PDI), ‘PDI5’, ‘PDI26’, and ‘PDI31’, and a commercially available systemic acquired resistance inducer, Actigard (drench; 2g/tree), applied two days before injection-infiltration with citrus canker bacterium Xcc (104 CFU/ml), on two-year-old Valencia trees. All three PDIs, sprayed at 500 ppm, as well as Actigard (drench), effectively reduced canker severity on the inoculated leaves in the greenhouse (P ≤0.02). In the grove, we tested new antimicrobials, Mastercop ‘MC’ (21.46% copper sulfate pentahydrate; metallic copper equivalent 5.4%) at concentrations of 1.12 kg/ha, 1.68 kg/ha and 2.24 kg/ha, ‘AM’ at 1.68 kg/ha and 2.24 kg/ha, and a nutrient solution (AGRO-MOS) at 1.12 kg/ha for canker suppression on 4–6-year-old Hamlin trees. Kocide 2000 (growers’ standard control; metallic copper equivalent 30%; 3.92 kg/ha) was used as a control check. Although 2021 was not as conducive for citrus canker due to the relatively dry spring months in the field, our results showed that the six sprays of AM (2.24 kg/ha) or MC (1.68 kg/ha, and 2.24 kg/ha), in 2022, provided excellent control of Xcc, with a significant reduction in disease incidence in leaves and fruits, and disease severity in fruits, similar to Kocide 2000. The results indicate that antimicrobials, AM and MC, and plant defense inducers PDI5, PDI26, and PDI31 can be part of an integrated pest management (IPM) program with copper for managing citrus canker. Reducing the frequency and amount of copper applications can help reduce pesticide and application expenses, lower risks of copper buildup in the soil and toxicity for citrus trees and reduce the risk of the emergence of copper-resistant Xcc strains. Further research on these products is needed to assess their long-term effectiveness and potential environmental risks.

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]

Sweet orange is an important citrus fruit grown throughout the world as it rich in phytonutrients properties and excellent source of vitamin C. The conventional clarification process involves more costs with personnel, equipment, and physical space. As an alternative, microfiltration (MF) has been applied in fruit juices for clarification. Clarification of sweet orange juice was carried out by microfiltration process using 0.2 μm size cellulose acetate MF membrane in a stirred cell. Flux decline was majorly due to deposits formed with soluble and suspended fraction of pectin, proteins and fibers, forming a low methoxy gel layer on membrane surface causing fouling during clarification. Long term flux decline was dictated by intermediate pore blocking in combination with growth of gel layer over the membrane surface. Reversible resistance was considered as domineering resistance and therefore, 90% of original permeate flux was recovered by following proper washing protocol to clean membranes. It was noticed that most of the total soluble solids (TSS), pH and vitamin C expressed as ascorbic acid of the feed were recovered in the permeate after filtration and there was no loss of the important properties pertaining to sweet orange juice. [ABSTRACT FROM AUTHOR]

An improved organogenesis protocol for multiplication of sweet orange cv. Mosambi has been standardized by the use of different PGRs, basal media and ethylene adsorbents. Incorporation of cytokinins, BAP (8.8 µM) and kinetin (6.97 µM) resulted in best shoot organogenesis with the highest response (81.40%), no. of micro-shoots/explant (2.06), mean micro-shoot length (1.30 cm) and no. of leaves/micro-shoot (3.55) owing to complementary effect of these factors. However, the regenerated micro-shoots failed to establish due to 100% leaf abscission of micro-shoot. To retard the effect of ethylene accumulation on the regenerated micro-shoots, two types of ethylene adsorbents carrying silver ions, namely, AgNO3 and Ag2S2O3 and two gelling agents (agar–agar and Phytagel™) were tested at different concentrations. Addition of AgNO3 (5.88 µM) to the medium containing Phytagel™ along with cytokinin (BAP 8.8 µM and kinetin 6.97 µM) led to significant reduction in shoot abscission rate (4.20), while 17.66 µM AgNO3 supplementation improved no. of micro-shoots/explants (2.19) and micro-shoot length (3.36 cm) whereas Ag2S2O3 at 20 µM enhanced the total chlorophyll content (3.47 mg g−1 FW) three times as compared to control. Similarly, among the tested basal media, MS basal medium induced best response on shoot organogenesis. Rooting of micro-shoots was highest (81.12%) with the supplementation of NAA (5.37 µM), which also affected no. of roots/explant (4.52) and mean root length (5.26 cm). The supplementation of ethylene adsorbents during in vitro micro-shoot multiplication significantly improved their quality, which provides ideal rooting for development of complete plantlets in sweet orange cv. Mosambi. Key message: Ethylene accumulation in glass containers inhibited micro-shoot establishment of Citrus sinensis L. Use of silver ions enhanced culture establishment and quality of the micro-shoot. [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.

Understanding of orchard nutrition status can facilitate the proper management of orchards for higher fruit yield and quality. From 2011 to 2019, the nutrition status of orchards in Hunan Province, a major citrus-producing area in china, were assessed. A total of 361 soil samples, 378 leaf samples and 285 fruit samples of sweet oranges including navel orange (citrus sinensis l. Osbeck ‘newhall’) and common sweet orange (citrus sinensis l. Osbeck ‘bingtangcheng’), and mandarins including satsuma mandarin (citrus unshiu marc. ‘miyagawa’) and ponkan (citrus reticulata blanco ‘xinnu’) were collected. These samples were from112 sweet orange orchards and 140 mandarin orchards. Parameters of soil, leaf and fruit nutrition and fruit quality were analyzed based on these samples. The results revealed that soil acidification occurred in 79.0% of sweet orange orchards (ph 3.56 to 8.12) and 74.7% of mandarin orchards (ph 2.75 to 8.15). Soil organic matter (om) was abundant in both sweet orange orchards (21.3 g/kg on average) and mandarin orchards (19.77 g/kg on average). Nutrient analysis demonstrated deficiencies of nitrogen (n), potassium (k) and boron (b) in soils and leaves of sweet orange and mandarin orchards. Zinc (zn) was abundant in soils but deficient in leaves, suggesting a low zn utilization efficiency in these orchards. Besides, excessive iron (fe), magnesium (mn) and copper (cu) were found in sweet orange and mandarin leaves, which may be associated with low soil ph and fungicides application in this area. The average contents of n, phosphorus (p) and k in the fruit were about 0.80%, 0.11% and 0.51%, respectively, with a ratio close to 1:0.14:0.6. Multiple linear regression (mlr) analysis revealed that leaf npk and molybdenum (mo) significantly affect fruit fresh fruit weight (ffw) and total soluble solids (tss), and leaf p is closely correlated with fruit titratable acid (ta).

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]

Accurate models for early harvest estimation in citrus production generally involve expensive variables. The goal of this research work was to develop a model to provide early and accurate estimations of harvest using low-cost features. Given the original data may derive from tree measurements, meteorological stations, or satellites, they have varied costs. The studied orchards included tangerines (Citrus reticulata x C. sinensis) and sweet oranges (C. sinensis) located in northeastern Argentina. Machine learning methods combined with different datasets were tested to obtain the most accurate harvest estimation. The final model is based on support vector machines with low-cost variables like species, age, irrigation, red and near-infrared reflectance in February and December, NDVI in December, rain during ripening, and humidity during fruit growth. Highlights: • Red and near-infrared reflectance in February and December are helpful values to predict orange harvest. • SVM is an efficient method to predict harvest. • A ranking method to A ranking-based method has been developed to identify the variables that best predict orange production.

Abstract Background Citrus species are among the most important and widely consumed fruit trees in the world and are subjected to increasing global cultivation. Sweet orange (Citrus sinensis L. Osbeck) is one of 30 species of citrus which is cultivated in different regions of Iran. In this study, 80 trees of 13 sweet orange cultivars of Mazandaran province were studied for genetic diversity and fingerprinting by five short simple repeat (SSR) marker. Results The studied cultivars showed a high degree of genetic variability with an average genetic polymorphism of 98.46%. Behshahr and Jadeh Ghadim2 genotypes had the highest and lowest values in Nei genetic diversity, number of effective alleles, and Shannon index, respectively. Based on k-means clustering, the studied genotypes were divided into two main different groups. The high magnitude of genetic similarity between replicates of different cultivars indicated a potential case of homonymy or synonymy. DAPC analysis showed genetic admixture among some of the cultivars. The heatmap plot illustrated the alleles involved in cultivar differentiation. The CAPs analysis of monomorphic alleles of SSR loci indicated that these alleles differ in their sequences which add up to the genetic variability of citrus germplasm. Conclusion In general, SSR markers, due to their codominant nature and abundance in genome, are a good indicator for cultivar fingerprinting and hybrid prediction in orange cultivars. The present results showed the high diversity of sweet orange trees in different cultivars in the north of the country.