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At least 19 recordsLinked to original sources
PubMed2026

Occurrence and Characterization of Graft-Transmissible Pathogens of Citrus in Orchards and Urban Citrus in Chile with a Focus on the Apscaviroid nanocitri.

Apscaviroid nanocitri (citrus dwarfing viroid, CDVd) is a graft-transmissible pathogen that frequently coexists with other citrus viroids and affects tree vigor. This study evaluated the occurrence of citrus viroids in small growers and commercial orchards in Chile and characterized CDVd strains obtained from urban Citrus spp. trees, with unknown propagation history following the discontinuation of the national citrus certification program. A total of 301 samples from five citrus-producing regions were analyzed, revealing that CDVd is widely distributed and commonly associated with Hostuviroid impedihumuli (hop stunt viroid, HSVd). Single infections were the most frequent (41%), followed by double (7.3%) and triple infections (3.0%), indicating that mixed infections are common. CDVd strains from urban trees were characterized using biological indexing on 'Etrog' citron Arizona 861-S-1 indicator plants combined with RT-PCR detection and phylogenetic analysis. Symptom development and pathogen detection were evaluated at 6 and 18 months post-inoculation. All graft-inoculated plants developed symptoms consistent with viroid infection, whereas control plants remained asymptomatic. CDVd was consistently detected at 18 months but not at earlier stages, suggesting delayed systemic accumulation. Although Closterovirus tristezae (citrus tristeza virus, CTV) was present in the source plants, it was not detected in indicator plants at either time point, possibly associated with the higher temperatures required for viroid symptom development during bioindexing. The frequent occurrence of mixed infections highlights the epidemiological relevance of viroid interactions and supports the need for reinstatement and strengthening of the national citrus certification program.

Apscaviroid nanocitri↗
PubMed2025

Molecular characterisation of a novel citrus-infecting emaravirus, citrus emaravirus 1.

The application of high-throughput sequencing (HTS) has accelerated the discovery of novel viruses and the genome sequencing of poorly characterised viruses in fruit crops, revealing a greater complexity of plant viromes than previously understood. Here, we report the identification and genomic characterisation of a novel emaravirus, tentatively named "citrus emaravirus 1" (CiEV1), from Citrus limon leaves collected in the North West Province of South Africa. HTS analysis identified contigs corresponding to the four conserved emaravirus genomic segments (RNA1-RNA4), each encoding characteristic proteins: RNA-dependent RNA polymerase, glycoprotein, nucleocapsid, and movement protein. Comparison of terminal sequences and phylogenetic analysis suggest placing CiEV1 within clade D of the genus Emaravirus (family Fimoviridae). To date, no association with symptoms has been identified. This is the first report of an emaravirus detected in citrus, expanding the known host range of the genus and contributing to the growing evidence of viral diversity in citrus. Further investigation is required to determine the epidemiological significance of CiEV1 in citrus orchards.

Citrus↗
PubMed2025

Targeting the "bitterness gene" by genome editing abolishes synthesis of bitter flavanones in citrus; prospects for new varieties and extended climates for cultivation.

Bitterness in citrus fruit is conferred by flavanone-neohesperidosides, whose accumulation is catalyzed by a single enzyme flavanone-7-O-glucosides-1,2-rhamnosyltransferase (1,2RhaT), expressed in both leaves and fruit. To eliminate citrus bitterness, we used CRISPR/Cas9 genome editing to inactivate the 1,2RhaT gene in grapefruit (Citrus paradisi) and "Carrizo" citrange (Citrus sinensis × Citrus trifoliata). Edited lines displayed frameshift mutations that introduced premature stop codons, effectively abolishing the synthesis of the bitter neohesperidosides naringin, neohesperidin, and poncirin. Metabolomic analyses in leaves from 1,2RhaT-mutant lines confirmed the absence of bitter flavanone-neohesperidosides and a compensatory increase in the tasteless flavanone-rutinosides hesperidin, didymin, and narirutin. Since 1,2RhaT is encoded by a single gene, our findings in leaves are expected to be identical for fruit and thus demonstrate a strategy for developing non-bitter citrus cultivars while retaining health-benefitting flavonoid levels. Furthermore, cold-hardy citrus species that are currently unacceptably bitter due to high flavanone-neohesperidoside levels may become useful sources for introduction of cold-hardiness following inactivation of the 1,2RhaT gene. This approach thus paves the way for expanding grapefruit markets and breeding cold-hardy, palatable citrus varieties that are better suited to a wider range of climates.

Flavanones↗
PubMed2025

In planta genome editing in citrus facilitated by co-expression of CRISPR/Cas and developmental regulators.

Recent advances in the field of genome editing offer a promising avenue for targeted trait improvements in fruit trees. However, the predominant method taken for genome editing in citrus (and other fruit trees) involves the time-consuming tissue culture approach, thereby prolonging the overall citrus breeding process and subjecting it to the drawbacks associated with somaclonal variation. In this study, we introduce an in planta approach for genome editing in soil-grown citrus plants via direct transformation of young seedlings. Our editing system, abbreviated here as IPGEC (in planta genome editing in citrus), is designed to transiently co-express three key gene groups in citrus tissue via Agrobacterium tumefaciens: (i) a genome-editing catalytic group, (ii) a shoot induction and regeneration group, and (iii) a T-DNA enhanced delivery group. This integrated system significantly improves de novo shoot induction and regeneration efficiency of edited tissue. By incorporating single-guides RNA's (sgRNA's) targeting the carotenoid biosynthetic gene PHYTOENE DESATURASE (CsPDS), the IPGEC system effectively produced mutated albino shoots, confirming its ability to generate homozygous/biallelic genome-edited plants. By using high throughput screening, we provide evidence that transgene-free genome-edited plants could be obtained following the IPGEC approach. Our findings further suggest that the efficiency of specific developmental regulators in inducing transformation and regeneration rates may be cultivar-specific and therefore needs to be optimized per cultivar. Finally, targeted breeding for specific trait improvements in already successful cultivars is likely to revolutionize fruit tree breeding and will pave the way for accelerating the development of high-quality citrus cultivars.

Citrus↗
PubMed2026

Application of compact CRISPR/Cas nucleases for citrus genome editing.

Gene editing technology continues to advance, and the range of available editing tools is steadily expanding. Recently, several compact and ultracompact systems have been developed, gaining considerable attention because their components can be efficiently packaged into viral vectors. To identify compact tools suitable for efficient genome editing in citrus, Casπ, CoCas9, along with their respective single guide RNAs, were synthesized, and CRISPR/Casπ and CRISPR/CoCas9 constructs were designed to assess their editing efficiency in 'Wanjincheng' orange (Citrus sinensis Osbeck). The Casπ was able to mediate genome editing in the citrus genome, although with low efficiency. In comparison, CoCas9 showed a transformation efficiency three times higher than that of the widely used SpCas9. Moreover, while the gene editing efficiency of CoCas9 was comparable to that of SpCas9, the significantly elevated transformation efficiency resulted in a significantly higher overall editing efficiency for CoCas9 relative to SpCas9. Mutation profiles generated by CoCas9 and SpCas9 were highly similar, and both nucleases displayed comparable target specificity at three potential off-target sites. These results indicate that Casπ is not suitable for application in citrus genome editing, whereas CoCas9 represents a promising alternative to SpCas9 for efficient and precise genome modification in citrus.

CRISPR-Cas Systems↗
PubMed2025

A high-quality chromosome-scale genome assembly of Xingan mandarin (Citrus reticulata 'Xingan'), a primitive Mandarin type.

Mandarin (Citrus reticulata) is broadly recognized as one of the foremost citrus crops globally. Our study identified the Xingan mandarin (Citrus reticulata 'Xingan') as a primitive type found near Maoer Mountain. This report provides a high-resolution, chromosome-scale genome assembly for the Xingan mandarin. The total size of the genome assembly is an impressive 325.12 Mb, including contig N50 and scaffold N50 values of 29.32 Mb and 29.62 Mb, respectively. Notably, we successfully anchored approximately 93.08% of the assembled sequences onto nine pseudochromosomes. Our predictions identified 30,581 protein-coding genes, 166 miRNAs, 415 tRNAs, 728 rRNAs, 325 snRNAs, and 659 snoRNAs. We were able to predict the functions of 27,242 genes, constituting 89.08% of the total protein-coding genes. A notable finding of our study was the high degree of genome synteny between the Xingan mandarin and the Mangshan mandarin (Citrus reticulata 'Mangshan'), reinforcing their genetic similarity. The acquisition of the chromosome-level genome for the Xingan Mandarin represents a significant milestone, laying an indispensable foundation for rigorous molecular investigations of this species. Moreover, it is poised to invigorate advanced research in comparative genomics within the Citrus genus.

Citrus↗
PubMed1976

Effects of citrus pulp in high urea rations for steers.

Effects of pelleted and conventional citrus pulp as a replacement for corn, with soybean meal added to keep protein comparable, were tested in rations with 5% urea and 33.33% sugarcane bagasse for fistulated steers. Thus, all rations were low in readily fermented carbohydrates other than those of corn or citrus pulp. Evaluation criteria were concentrations of urea in blood and of pH, ammonia, and volatile fatty acids of rumen fluid. Citrus pulp for diets 1, 2, 3, and 4 was 0, 19, 38, or 55%. Rumen fluid and blood were sampled 1 h before and 2, 4, 7, and 12 h after feed was placed directly into the rumen. No differences between pelleted and conventional pulp or among time trends were significant except that for both forms rumen ammonia was lower with the two highest percents of citrus pulp. Addition of citrus pulp at 0, 19, 38, or 55% of the ration reduced rumen pH (6.85, 6.65, 6.61, 6.51). Blood urea and rumen ammonia decreased in steers fed 19, 38, or 55% pulp; thus, the acetic to propionic ratio was higher. Butyric acid changed only in the time trend. Total volatile fatty acid concentrations were higher at 19, 38, and 55% than at 0% pulp. They were higher at 38 and 55 than at 19%.

Ammonia↗
PubMed2025

Transgene-free genome editing in citrus and poplar trees using positive and negative selection markers.

Transgene-free genome editing of the gene of interest in citrus and poplar has been achieved by co-editing the ALS gene via transient transgene expression of an efficient cytosine base editor. CRISPR-Cas genome editing systems have been widely used in plants. However, such genome-edited plants are nearly always transgenic in the first generation when Agrobacterium-mediated transformation is used. Transgene-free genome-edited plants are valuable for genetic analysis and breeding as well as simplifying regulatory approval. It can be challenging to generate transgene-free genome-edited plants in vegetatively propagated or perennial plants. To advance transgene-free genome editing in citrus and poplar, we investigated a co-editing strategy using an efficient cytosine base editor (CBE) to edit the ALS gene to confer herbicide resistance combined with transient transgene expression and potential mobile RNA-based movement of CBE transcripts to neighboring, non-transgenic cells. An FCY-UPP based cytotoxin system was used to select non-transgenic plants that survive after culturing on 5-FC containing medium. While the editing efficiency is higher in poplar than in citrus, our results show that the CBE-based co-editing strategy works in both citrus and poplar, albeit with low efficiency for biallelic edits. Unexpectedly, the addition of the TLS mobile RNA sequence reduced genome editing efficiency in both transgenic and non-transgenic plants. Although a small fraction of escaping plants is detected in both positive and negative selection processes, our data demonstrate a promising approach for generating transgene-free base-edited plants.

Populus↗
PubMed2026

CgMYC2 directly activates jasmonate-induced naringin biosynthesis in Citrus grandis 'Tomentosa'.

CgMYC2 links jasmonate signaling to naringin biosynthesis by binding G-box motifs and activating flavonoid-pathway promoters in Citrus grandis 'Tomentosa' Naringin, the predominant bitter-flavanone glycoside in Citrus grandis 'Tomentosa', has well-characterized biosynthetic enzymes, yet the transcriptional regulators coupling hormonal signals to pathway activation remain poorly understood. We demonstrate that CgMYC2, a jasmonate-responsive bHLH transcription factor, functions as a central activator of naringin biosynthesis. Exogenous methyl jasmonate (MeJA) treatment increased naringin content 3.45-fold in seedlings, coinciding with a rapid 6.6-fold induction of CgMYC2 that preceded the peak transcription of five core biosynthetic genes (CgPAL5, CgCHS, CgFNS, Cg7GlcT, and Cg1,2RhaT). Physical interaction between CgMYC2 and the JAZ protein CgJAZ3 was confirmed by pull-down and Co-IP assays, placing CgMYC2 within the canonical jasmonate signaling cascade. Y1H confirmed CgMYC2 binding to the Cg1,2RhaT promoter, EMSA demonstrated direct G-box-dependent binding to all five pathway promoters, and dual-luciferase assays showed transactivation of all five promoters, with the strongest activation for CgCHS. As complementary chromatin-level support, a single-sample CUT&Tag profile revealed G-box-enriched CgMYC2-associated chromatin regions across jasmonate-responsive and secondary-metabolic loci. Virus-induced gene silencing (VIGS) of CgMYC2 reduced naringin content by ~21% and suppressed biosynthetic gene expression, supporting its positive contribution. Furthermore, heterologous overexpression in tomato activated the flavonoid pathway and elevated 16 flavonoid compounds, consistent with evolutionary conservation of the MYC2-G-box regulatory logic. These findings establish CgMYC2 as a central, JA-responsive activator bridging jasmonate perception and naringin biosynthesis, providing a molecular framework for the targeted improvement of bitter-flavonoid traits in citrus.

Citrus↗
PubMed2026

High-efficiency genome-editing, transgene evaluation, and antimicrobial efficacy testing using Citrus medica L. hairy roots.

Huanglongbing (HLB) disease, associated with the fastidious bacterium Candidatus Liberibacter asiaticus (CLas), has a significant impact on citrus production worldwide. Conventional biochemical and genetic evaluation studies to identify potential disease resistance strategies have been mainly hindered due to the inability to culture CLas in a defined medium and the general recalcitrance of Citrus cultivars (grapefruits and oranges) to Agrobacterium-mediated plant transformation. We previously demonstrated the utility of plant hairy roots to co-cultivate CLas. In this study, we developed a hairy root transformation system using citron (Citrus medica L.), which is highly amenable to Rhizobium-mediated hairy root transformation. The explant survival and hairy root transformation efficiencies were up to 100% and 73%, respectively, and transgenic roots can be attained in as little as 30-60 days. We demonstrate the utility of this citron-based hairy root transformation for rapid CRISPR/Cas9-mediated gene editing, transgene evaluation, and antimicrobial efficacy testing. The citron-based hairy root transformation system will significantly help the research community to speed-track the assessment of potential HLB disease resistance strategies.

Citrus↗
PubMed2026

A CsWRKY46-CsPBL9-CsARI1 tripartite regulatory module coordinates H2O2 production and callose deposition in citrus fruit immunity.

Plant immunity against pathogens involves multiple immune responses and intricate regulatory networks. However, how immune networks are deployed in fruit remains poorly understood. Here, we show that citrus fruit immune responses, including hydrogen peroxide (H2O2) production and callose deposition, are multiply regulated by transcriptional activation, phosphorylation, and ubiquitination. Citrus sinensis genes encoding nicotinamide adenine dinucleotide phosphate (NADPH) oxidase CsRBOHG and callose synthase CsCalS5, responsible for H2O2 production and callose deposition, respectively, are transcriptionally activated by CsWRKY46. Phosphorylation-enhanced activity of CsRBOHG by CsPBL9 enhances immunity. RING1-IBR-RING2 (RBR)-type E3 ligase CsARI1, acting as an immune brake, ubiquitinates CsRBOHG and CsCalS5 for degradation. Interestingly, CsARI1 also shows a moonlight function wherein it interacts with CsPBL9 in a non-ubiquitination manner, disrupting CsPBL9's interaction with CsRBOHG. This CsARI1-CsPBL9 interaction is stimulated by H2O2 as feedback. Moreover, H2O2 contributes to callose deposition, indicating an interplay between two immune responses. Our study reveals a tripartite regulatory hub orchestrating self-linked immunity in citrus fruit.

CP: plants↗
PubMed2026

Genome-wide association studies of plant traits and functional analysis of leaf development-related genes in citrus.

Labor-saving and high-light-efficiency tree architecture is a key breeding objective for woody fruit trees like citrus. However, population genetics information on these traits remains limited. In this study, tree architecture, thorn, and leaf traits were evaluated in 353 F2 progeny derived from a cross between Clementine mandarin and precocious trifoliate orange-an early-flowering variety. A random subset of 300 offspring was sequenced for a genome-wide association study (GWAS), which detected 10 216 significantly associated SNPs and defined several major quantitative trait loci (QTLs) for the target traits. Subsequent bulked segregant analysis (BSA) and GWAS on individuals with extreme compound leaf phenotypes mapped the causal gene(s) to a 0.8 Mb region (22.15-22.95 Mb) on chromosome 4. Genetic analysis across multiple hybrid combinations confirmed that the compound leaf trait in trifoliate orange is dominantly inherited and follows Mendelian segregation. Transcriptome profiling of parental leaves at different developmental stages identified a KNOX gene, CiKNAT6, as a candidate. Further validation using CAPS markers and Hi-Tom sequencing demonstrated tight linkage between an InDel polymorphism in CiKNAT6 and leaf shape across diverse citrus species and the F2 population, with co-segregation observed for the compound leaf trait. Due to alternative splicing producing seven splice variants, the CiKNAT6 DNA sequence was selected for genetic transformation experiments. Functional analysis revealed that the Clementine mandarin allele of CiKNAT6 is non-functional owing to an InDel, whereas ectopic expression of the trifoliate orange allele in tobacco and lemon induced leaf curling and reduced leaf size. CRISPR-Cas9 knockout of CiKNAT6 in trifoliate orange resulted in increased leaf area. These findings provide valuable genetic resources and insights for future studies on tree architecture and leaf morphology.

Plant Leaves↗
PubMed2026

Development of a Droplet-Based RNA Interference Feeding Assay for Neonates of the Citrus Root Weevil Diaprepes abbreviatus.

The citrus root weevil, Diaprepes abbreviatus, is an economically important pest of citrus and ornamental crops whose subterranean larval feeding damages roots and predisposes plants to secondary pathogen infection. Development of efficient RNA interference (RNAi) delivery methods for early larval stages is essential for functional genomics studies and the evaluation of RNAi-based pest management strategies. In this study, we developed a droplet-based feeding assay for oral delivery of double-stranded RNA (dsRNA) to neonates of D. abbreviatus using chitin synthase 2 (DaCHS2) as a model RNAi target to validate the assay. Feeding solutions containing dsRNA were supplemented with sucrose and bromophenol blue dye, with bromophenol blue used to visually confirm ingestion. Across three independent biological replicates, all neonates exposed to DaCHS2-dsRNA, GFP-dsRNA, and water control droplets were confirmed to have ingested the feeding solution (45/45 neonates per treatment; 100% feeding success). Oral delivery of dsRNA targeting DaCHS2 reduced transcript abundance and was associated with developmental abnormalities and mortality, including incomplete molting, abnormal pigmentation, cuticular deformities, defective pupation, and malformed adults. Regression analysis demonstrated moderate and significant relationship between dsRNA concentration and neonate mortality and developmental abnormalities. RT-qPCR further confirmed reduced DaCHS2 transcript abundance following oral dsRNA exposure. The developed assay provides a simple, reproducible, and minimally invasive proof-of-concept platform for oral dsRNA delivery to D. abbreviatus neonates. The assay requires only small dsRNA volumes, provides visual confirmation of ingestion, and may facilitate laboratory-based screening of additional RNAi target genes in D. abbreviatus and other coleopteran pests.

Animals↗
PubMed2026

De novo transcriptome meta-analysis reveals candidate genes involved in life-stage transitions for RNAi-mediated management of the citrus root weevil (Diaprepes abbreviatus).

BACKGROUND: The citrus root weevil, Diaprepes abbreviatus, is a destructive agricultural pest for which molecular control options remain limited due to historically sparse genomic resources. Leveraging a comprehensive de novo transcriptome, we investigated developmental gene regulation across larval, pupal, and adult stages and identified essential targets for RNA interference (RNAi)-based intervention. RESULTS: Stage-resolved transcriptomic analyses revealed extensive transcriptional reprogramming associated with metabolism, detoxification, cuticle biosynthesis, endocrine signaling, and sensory perception. Among these, chitin synthase (DaCHS) emerged as a critical developmental gene, exhibiting pronounced up-regulation during late larval and pupal stages corresponding to intensive cuticle synthesis. Phylogenetic and structural analyses demonstrated that DaCHS is highly conserved among insects and retains canonical catalytic domains and transmembrane topology. Alpha Fold-based structural modeling and molecular docking confirmed stable interaction of DaCHS with its substrate, N-acetylglucosamine, supporting functional conservation of enzymatic activity. Oral delivery of DaCHS double-stranded RNA induced robust transcript suppression, leading to significant mortality and severe developmental defects, including larval and pupal abnormalities, and adults with disrupted wing and abdominal morphogenesis. CONCLUSION: These findings establish DaCHS as an indispensable gene for D. abbreviates development and validate transcriptome-guided RNAi as a powerful framework for target discovery. This work provides a strong molecular foundation for developing RNAi-based strategies that can be integrated into sustainable management programs for citrus root weevil control. © 2026 Society of Chemical Industry.

Animals↗
PubMed2025

Based on network pharmacology, molecular docking, and validation experiments to investigate the active components and mechanisms of action of Tibetan Medog County Citrus medica L.: In antioxidant activity.

BACKGROUND: The antioxidant potential of citrus plants is closely related to their geographical origin, making it crucial to evaluate the natural antioxidant properties of Citrus medica L. (C. medica) from Medog County, Tibet. METHODS: This study systematically investigates the antioxidant mechanisms of C. medica using network pharmacology, molecular docking, and experimental assays. RESULTS: The antioxidant activity experiments showed that C. medica exhibits good bioactivity, and the fruit has better antioxidant activity than the leaves. Network pharmacology revealed 11 active components of C. medica with 1547 antioxidant-related targets. Key targets include TP53, IL6, AKT1, STAT3, and TNF. Gene ontology (GO) analysis identified 1419 biological process entries, 147 cellular component entries, and 306 molecular function entries. Kyoto Encyclopedia of Genes and Genomes analysis identified 212 antioxidant-related signaling pathways. The GO and Kyoto Encyclopedia of Genes and Genomes enrichment analyses showed that the targets are involved in cancer pathways, protein binding, enzyme binding, lipid metabolism, and atherosclerosis. Molecular docking demonstrated that the 11 active components of Medog C. medica exhibit binding energies with core targets TP53, IL6, AKT1, STAT3, and TNF generally less than -5 kcal·mol-1, indicating good affinity. CONCLUSION: This study identifies the excellent antioxidant activity of C. medica from multiple aspects and elucidates its potential antioxidant mechanisms, providing a theoretical basis for the development and application of C. medica as an antioxidant functional additive.

Molecular Docking Simulation↗
PubMed1979

Acephate and methamidophos residue behavior in Florida citrus, 1976.

The half-life of acephate and its hydrolysate, methamidophos, in the rind of Temple and Valencia oranges, and grapefruit, lemons, and tangerines was 10.3 days and 10.5 days, respectively. Half-lives of acephate and methamidophos in citrus pulp were 15.0 days and 6.1 days, respectively based on 7-, 14-, and 21-day data. Seven days after treatment, acephate and methamidophos reached maximum levels in rind and pulp. Acephate residue levels in rind were less than 3.0 ppm 14 days after treatment; acephate residues in pulp were less than 3.0 ppm throughout the experiment. Methamidophos residue levels averaged less than 0.25 ppm after 21 days.

Absorption↗
PubMed1979

Gas-liquid chromatographic determination of thiourea in citrus peels.

A gas-liquid chromatographic (GLC) method was developed for the detection and determination of thiourea in citrus peels. After the peel is extracted with ethyl ether, the ether extract is adsorbed on sodium sulfate together with water. Thiourea is recoverd from both the sodium sulfate and the peel residue with ethyl acetate-acetone(2+1). The extracted mixture is cleaned on an alumina column, the eluate is concentrated under vacuum, and thiourea is extracted from the concentrate with sodium carbonate solution. GLC was carried out on the prepared benzoyl derivative of thiourea. The average recoveries of thiourea from lemon peel were 85.3, 93.1, and 97.6% at the fortification levels of 1, 10, and 100 ppm, respectively. The detection limit was low as 0.08 ppm.

Chromatography, Gas↗