Search

Pomelo peel is a valuable source of pectin, but research on its cell wall polysaccharides is limited. This study compared the cell wall polysaccharides of pomelo peel, enzyme-extracted polysaccharides of pomelo peel, and enzyme-extracted polysaccharides of whole pomelo fruit. Cell wall polysaccharides, including water-soluble pectin (WSP), chelator-soluble pectin (CSP), sodium carbonate-soluble pectin (NSP), 1 mol/L KOH soluble hemicellulose (KSH-1), and 4 mol/L KOH soluble hemicellulose (KSH-2), were obtained by sequence-extraction method. Total polysaccharides from whole pomelo fruit (TP) and peel-polysaccharides from pomelo pericarps (PP) were obtained using enzyme-extraction method. The structural, thermal, rheological, antioxidant properties, and wound healing effect in vitro were described for each polysaccharide. WSP had a uniform molecular weight distribution and high uronic acid (UA) content, suitable for commercial pectin. NSP had the highest Rhamnose (Rha)/UA ratio and a rich side chain with highest viscosity and water retention. PP displayed the highest DPPH radical scavenging activity and reducing capacity at 0.1 to 2.0 mg/mL concentration range, with an IC 50 of 1.05 mg/mL for DPPH free radicals. NSP also demonstrated the highest hydroxyl radical scavenging activity and promoted Human dermal keratinocyte proliferation and migration at 10 μg/mL, suggesting potential applications in daily chemical and pharmaceutical industries., Competing Interests: Declaration of competing interest The authors declare that there is no conflict of interest regarding the publication of this article., (Copyright © 2024. Published by Elsevier B.V.)

Granulation of juice sacs is a physiological disorder, which affects pomelo fruit quality. Here, the transcriptome and ubiquitinome of the granulated juice sacs were analyzed in Guanxi pomelo. We found that lignin accumulation in the granulated juice sacs was regulated at transcription and protein modification levels. In transcriptome data, we found that the genes in lignin biosynthesis pathway and antioxidant enzyme system of the granulated juice sacs were significantly upregulated. However, in ubiquitinome data, we found that ubiquitinated antioxidant enzymes increased in abundance but the enzyme activities decreased after the modification, which gave rise to reactive oxygen species (ROS) contents in granulated juice sacs. This finding suggests that ubiquitination level of the antioxidant enzymes is negatively correlated with the enzyme activities. Increased H 2 O 2 is considered to be a signaling molecule to activate the key gene expressions in lignin biosynthesis pathway, which leads to the lignification in granulated juice sacs of pomelo. This regulatory mechanism in juice sac granulation of pomelo was further confirmed through the verification experiment using tissue culture by adding H 2 O 2 or dimethylthiourea (DMTU). Our findings suggest that scavenging H 2 O 2 and other ROS are important for reducing lignin accumulation, alleviating juice sac granulation and improving pomelo fruit quality., (© 2024. The Author(s).)

Maturity determination of pomelo fruits having health-benefiting attributes is an important issue to enhance the quality of harvesting. Here, an interdigitated electrode (IDE) based sensor is introduced to detect its maturity by determining the naringin content. The sensor was made by depositing amberlite IRA-400 as a sensing layer on IDE patterned PCB substrate at room temperature with hydrothermal and spin-coating techniques. The sensor exhibits excellent selectivity for naringin, high sensitivity of 0.008 µA for 10 ppb of naringin, and reusability up to 3-4 times for naringin quantification in maturity testing of fruits. The pomelo fruits start to mature when maximum values of current response and naringin content are found at 140 DAFS. The naringin content decreases as maturity progresses and maximum phytochemical attributes were obtained at 180-220 DAFS. The IDE sensor assures an appropriate period of plucking of pomelo fruits improving harvesting practices and trade of citrus fruits., (Copyright © 2021. Published by Elsevier Ltd.)

Juice sac granulation (a physiological disorder) leads to large postharvest losses of pomelo ( Citrus maxima ). Previous studies have shown that juice sac granulation is closely related to lignin accumulation, while the molecular mechanisms underlying this disorder remain elusive in pomelo. Our results showed that the lignin content in NC (near the core) and FC (far away from the core) juice sacs overall increased from 157 DPA (days post anthesis) to 212 DPA and reached a maximum at 212 DPA. Additionally, the lignin content of NC juice sacs was higher than that of FC juice sacs. In this study, we used transcriptome-based weighted gene co-expression network analysis (WGCNA) to address how lignin formation in NC and FC juice sacs is generated during the development of pomelo. After data assembly and bioinformatic analysis, we found a most correlated module (black module) to the lignin content, then we used the 11 DEGs in this module as hub genes for lignin biosynthesis. Among these DEGs, PAL (phenylalanine ammonia lyase), HCT (hydroxycinnamoyl-CoA shikimate/quinate hydroxycinnamoyl transferase), 4CL 2 (4-coumarate: CoA ligase), C4H (cinnamate 4-hydroxylase), C3'H ( p (caffeoyl CoA 3-Omethyltransferase) were the most distinct DEGs in granulated juice sacs. Co-expression analysis revealed that the expression patterns of several transcription factors such as MYB, NAC, OFP6, and bHLH130 are highly correlated with lignin formation. In addition, the expression patterns of the DEGs related to lignin biosynthesis and transcription factors were validated by qRT-PCR, and the results were highly concordant with the RNA-seq results. These results would be beneficial for further studies on the molecular mechanism of lignin accumulation in pomelo juice sacs and would help with citrus breeding.CCoAOMT 1 (caffeoyl CoA 3-Omethyltransferase) were the most distinct DEGs in granulated juice sacs. Co-expression analysis revealed that the expression patterns of several transcription factors such as MYB, NAC, OFP6, and bHLH130 are highly correlated with lignin formation. In addition, the expression patterns of the DEGs related to lignin biosynthesis and transcription factors were validated by qRT-PCR, and the results were highly concordant with the RNA-seq results. These results would be beneficial for further studies on the molecular mechanism of lignin accumulation in pomelo juice sacs and would help with citrus breeding.

'Liuyuezaoyou' is an early-ripening cultivar selected from a bud mutation of Citrus grandis Osbeck 'Guanximiyou'. They were designated here as MT and WT, respectively. The fruit of MT matures about 45 days earlier than WT, which was accompanied by significant changes in key phytohormones, sugar compounds and organic acids. Recent studies have showed that microRNAs (miRNAs) play an important role in regulation of fruit ripening process. The aim of this study was to compare MT fruits with WT ones to uncover if miRNAs were implicated in the ripening of C. grandis . Fruits of both WT and MT at four developmental stages were analyzed using high-throughput sequencing and RT-PCR. Several independent miRNA libraries were constructed and sequenced. A total of 747 known miRNAs were identified and 99 novel miRNAs were predicted across all libraries. The novel miRNAs were found to have hairpin structures and possess star sequences. These results showed that transcriptome and miRNAs are substantially involved in a complex and comprehensive network in regulation of fruit ripening of this species. Further analysis of the network model revealed intricate interactions of miRNAs with mRNAs during the fleshy fruit ripening process. Several identified miRNAs have potential targets. These include auxin-responsive protein IAA9, sucrose synthase 3, V-type proton ATPase, NCED1 (ABA biosynthesis) and PL1/5 (pectate lyase genes), as well as NAC100 putative coordinated regulation networks, whose interactions with respective miRNAs may contribute significantly to fruit ripening of C. grandis .

Pomelo is rich in bioactive compounds (carotenoids, phenolics and essential oil) in the early stage of fruit development, but it is often wasted in the cultivation and management process. To gain an insight into the carotenoid metabolism pathway in pomelo, the carotenoid profiles and the expression patterns of carotenogenic genes were investigated in two genotypes of pomelo during early fruit development. The results showed that a higher carotenoid content was observed in honey pomelo as compared with golden pomelo, which may be related to different gene regulation mechanisms. Lutein, α-carotene, and β-carotene were the main carotenoids in pomelo young fruit, and lutein was the highest one. The accumulation of carotenoids during fruit early development in honey pomelo is related to the transcriptional regulation of ZISO and LUT5 . In golden pomelo, the rate-limiting gene for carotenoids is PDS and ZDS . In addition, the expression of seven genes except CRTISO in honey pomelo was higher than that in golden pomelo. The results are helpful to further clarify the regulatory mechanism of carotenoid accumulation during early fruit development and provide a direction for the high-value utilization of young fruits in pomelo.

Citrus grandis or Citrus maxima , widely recognized as Pomelo is widely cultivated in many countries because of their large amounts of functional, nutraceutical and biological activities. In traditional medicine, various parts of this plant including leaf, pulp and peel are used for generations as they are scientifically proven to have therapeutic potentials and safe for human use. The main objective of this study was to review the different therapeutic applications of Citrus grandis and the phytochemicals associated with its medicinal values. In this article different pharmacological properties like antimicrobial, antitumor, antioxidant, anti-inflammatory, anticancer, antiepileptic, stomach tonic, cardiac stimulant, cytotoxic, hepatoprotective, nephroprotective, and anti-diabetic activities of the plant are highlighted. The enrichment of the fruit with flavonoids, polyphenols, coumarins, limonoids, acridone alkaloids, essential oils and vitamins mainly helps in exhibiting the pharmacological activities within the body. The vitamins enriched fruit is rich in nutritional value and also has minerals like calcium, phosphorous, sodium and potassium, which helps in maintaining the proper health and growth of the bones as well as the electrolyte balance of the body. To conclude, various potential therapeutic effects of Citrus grandis have been demonstrated in recent literature. Further studies on various parts of fruit, including pulp, peel, leaf, seed and it essential oil could unveil additional pharmacological activities which can be beneficial to the mankind.

Background: Pomelo is one of the three major species of citrus. The fruit accumulates a variety of abundant secondary metabolites that affect the flavor. UDP-glycosyltransferases (UGTs) are involved in the glycosylation of secondary metabolites., Results: In the present study, we performed a genome-wide analysis of pomelo UGT family, a total of 145 UGTs was identified based on the conserved plant secondary product glycosyltransferase (PSPG) motif. These UGT genes were clustered into 16 major groups through phylogenetic analysis of these genes with other plant UGTs (A-P). Pomelo UGTs were distributed unevenly among the chromosomes. At least 10 intron insertion events were observed in these UGT genome sequences, and I-5 was identified to be the highest conserved one. The expression profile analysis of pomelo UGT genes in different fruit tissues during development and ripening was carried out by RNA-seq., Conclusions: We identified 145 UGTs in pomelo fruit through transcriptome data and citrus genome database. Our research provides available information on UGTs studies in pomelo, and provides an important research foundation for screening and identification of functional UGT genes.

The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama, is the only natural vector of bacteria responsible for Huanglongbing (HLB), a worldwide destructive disease of citrus. ACP reproduces and develops only on the young leaves of its rutaceous host plants. Olfactory stimuli emitted by young leaves may play an important role in ACP control and HLB detection. In this study, volatile organic compounds (VOCs) from healthy and HLB-infected young leaves of navel orange and pomelo were analyzed by headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS). A total of 36 compounds (including dimers or polymers) were identified and quantified from orange and 10 from pomelo leaves. Some compounds showed significant differences in signal intensity between healthy and HLB-infected leaves and may constitute possible indicators for HLB infection. Principal component analysis (PCA) clearly discriminated healthy and HLB-infected leaves in both orange and pomelo. HS-GC-IMS was an effective method to identify VOCs from leaves. This study may help develop new methods for detection of HLB or find new attractants or repellents of ACP for prevention of HLB.

Visible/near-infrared (VIS/NIR) spectroscopy is a powerful tool for rapid, nondestructive fruit quality detection. This technology has been widely applied for quality detection of small, thin-peeled fruit, though less so for large, thick-peeled fruit due to a weak spectral signal resulting in a reduction of accuracy. More modeling work should be focused on solving this problem. "Shatian" pomelo is a traditional Chinese large, thick-peeled fruit, and granulation and water loss are two major internal quality factors that influence its storage quality. However, there is no efficient, nondestructive detection method for measuring these factors. Thus, the VIS/NIR spectral signal detection of 120 pomelo samples during storage was performed. Information mining (singular sample elimination, data processing, feature extraction) and modeling were performed in different ways to construct the optimal method for achieving an accurate detection. Our results showed that the water content of postharvest pomelo was optimally detected using the Savitzky-Golay method (SG) plus the multiplicative scatter correction method (MSC) for data processing, genetic algorithm (GA) for feature extraction, and partial least squares regression (PLSR) for modeling (the coefficient of determination and root mean squared error of the validation set were 0.712 and 0.0488, respectively). Granulation degree was best detected using SG for data processing and PLSR for modeling (the detection accuracy of the validation set was 100%). Additionally, our research showed a weak relationship between the pomelo water content and granulation degree, which provided a reference for the existing debates. Therefore, our results demonstrated that VIS/NIR combined with optimal information mining and modeling methodswas feasible for determining the water content and granulation degree of postharvest pomelo, and for providing references for the nondestructive internal quality detection of other large, thick-peeled fruits.

This study utilized pomelo steam distillation to isolate pomelo peel essential oil. The constituents were then analyzed through gas chromatography-mass spectrometry (GC-MS), and the antibacterial activity of the essential oil emulsions at different homogenizer speed conditions and concentrations of water-soluble chitosan (degree of acetylation, DA = 54.8%) against S. aureus and E. coli was examined. Analysis of the essential oil composition identified a total of 33 compounds with the main constituent, limonene accounting for 87.5% (940.07 mg/g) of the total. The pomelo peel oil was emulsified through homogenization at 24,000 rpm, resulting in a minimal inhibitory concentration (MIC) for E. coli that was 1.9 times lower than that of the essential oil without homogenization. In addition, a mixture of 0.4% essential oil emulsion and 0.03% water-soluble chitosan had the strongest synergetic antibacterial effect on S. aureus and E. coli at pH 7.4. In comparison with chitosan alone, the MIC value of this mixture was significantly 2.4 and 2.5 times lower. Hence, this study suggests using a mixture of emulsified pomelo peel oil and water-soluble chitosan to develop a novel natural food preservative, and that the processability of food, as well as the economic value of the byproducts of the Taiwan Matou pomelo and chitosan, could be increased., Competing Interests: The authors declare no conflict of interest.

Food intake has a great influence on blood glucose in patients with diabetes. This study was to determine the glycemic index (GI) and glycemic load (GL) of a particular pomelo named Majia pomelo and its effects on postprandial glucose (PPG) in patients with type 2 diabetes (T2D). Twenty healthy subjects and 20 T2D patients (controlled on lifestyle measures and/or metformin) were tested on 2 separate days with 50 g of glucose and 50 g equivalent of carbohydrates from Majia pomelo for GI measurement. To test effects of Majia pomelo on PPG, 19 hospitalized T2D patients (controlled on insulin therapy) were selected for a 9-day study. The dose of insulin for each patient was adjusted on the first 3 days. A total of 100 mg Majia pomelo was consumed per meal in the last 3 tested days. Blood glucose was measured to evaluate the glycemic excursions. The GIs for Majia pomelo in healthy individuals and T2D patients were 78.34±1.88 and 72.15±1.95 respectively. The value of GL was as low as 4.23 in diabetic patients with serving size of 100 g pomelo, indicting Majia pomelo as a high GI but low GL fruit. Consumption of Majia pomelo in hospitalized T2D patients did not cause significant glucose fluctuation. It was concluded that high GI pomelo can serve as a low GL fruit if it is consumed with a limited daily amount and thus can be supplied to diabetic patients. These results may mean more varieties of food choices for T2D patients.

A microwave pretreatment method was developed to preserve pectin, naringin, and limonin contents in pomelo flavedo to allow for longer storage times and subsequent extraction of pomelo essential oil. In terms of the essential oil, microwave pretreatment performed better than hydrodistillation with respect to extraction efficiency (1.88±0.06% in 24min versus 1.91±0.08% in 240min), oxygenation fraction (48.59±1.32% versus 29.63±1.02%), energy consumption (0.15kWh versus 1.54kWh), and environmental impact (123.20g CO 2 versus 1232g CO 2 ). Microwave-pretreated samples retained higher amounts of pectin, naringin, and limonin compared with non-pretreated samples. No obvious change in the degree of pectin esterification was observed. This study shows that the proposed process is a promising methodology for both preserving valuable compounds in pomelo flavedo during storage and acquiring essential oils., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

3-Methyl-1-(4-sulfonylbutyl) imidazolium hydrogensulfate, [HO 3 S(CH 2 ) 4 mim]HSO 4 , was applied as an extractant in an ultrasound-microwave synergistic extraction approach to substitute conventional solvent for the extraction of pectin from the albedo part of pomelo peels. The analysis of variance (ANOVA) test and response surface method were employed for the optimization of the extraction conditions. A pectin yield of 328.64±4.19mg/g was achieved using the obtained optimal conditions, which was significantly higher than yields of conventional methods with reference solvents. Pectin samples extracted with [HO 3 S(CH 2 ) 4 mim]HSO 4 and hydrochloric acid solutions were tested by ANOVA and showed no significant differences in total carbohydrate content and degree of esterification; while galacturonic acid content was significantly different for the pectin from each extraction solvents. The differences revealed from images of atomic force microscopy and scanning electron microscope, Fourier transform infrared spectroscopy, and thermogravimetric analysis suggested the physiochemical properties of pectin could be affected by the extraction solvent. The [HO 3 S(CH 2 ) 4 mim]HSO 4 proved to be a promising alternative to conventional solvents and the proposed method is efficient for the extraction of pectin from the albedo of pomelo peels., (Copyright © 2016 Elsevier B.V. All rights reserved.)

The aim of this study was to investigate the effect of pomelo pulp on the pharmacokinetics of cyclosporine in healthy male Thai volunteers. The study design was an open-label, randomized, single dose, crossover study with a 2-week washout period. A single oral dose of 2 × 100 mg cyclosporine was administered with 200 mL of water. Each subject received 250 g of pomelo pulp or 250 mL of water 1 hour before drug administration and once again 10 minutes following drug administration. Blood samples were collected over a 24 hour period. The point estimates (90% confidence intervals) of the test/control ratio using logarithmic transformed data for the area under the curve (AUC) for blood concentration from time 0 to infinity (AUC(0- ∞)) and the observed maximum concentration (C(max)) were 128.8% (120.6-137.6) and 136.1% (126.0-146.8), respectively. These 90% confidence intervals were higher than the accepted bioequivalence range defined by the European Medicines Agency guidelines for narrow therapeutic index drugs (90%-111% for AUC and 80%-125% for C(max)). However, the apparent terminal half-life (t(1/2)) was not significantly different. In conclusion, co-administration of cyclosporine and pomelo pulp increased the relative bioavailability of cyclosporine., (© 2014, The American College of Clinical Pharmacology.)

Eighty pomelo samples and 80 soil samples were examined using a multielement component test to predict the geographical origins of pomelos produced in 4 regions (Sichuan, Chongqing, Fujian, and Guangxi Provinces) of China. The concentrations of 8 elements were determined by atomic absorption spectrometry. Ca, K, and Na were the most abundant elements. Principal component analysis (PCA) and linear discriminant analysis (LDA) were applied to reduce the dimensionality of the multielement data from 8 to 2 while retaining the highest possible variance. Using PCA and LDA, 69.66% and 91.30%, respectively, of the pomelo origins were classified correctly using multielement variables, along with 67.06% and 83.40% for soil multielement analysis. Results indicated that the LDA method was more effective for geographical origin classification than PCA. The results of the multielement component test demonstrated its capability to screen pomelo origins rapidly., (© 2015 Institute of Food Technologists®)

Unlabelled: A method was established for purification of limonin, nomilin, and isoobacunoic acid simultaneously from segment membranes of pomelo (Citrus Grandis). This method includes 3 steps, removing most impurities by macroporous resin HZ-816, isolating limonin by High Speed Counter Current Chromatography (HSCCC), and isolating nomilin and isoobacunoic acid by semi-preparative HPLC. Naringin was partially purified as a by-product of this process using Sephadex LH-20. All limonoids purified through this method reached 95% purity. The purified limonin, nomilin and isoobacunoic acid were identified according to the retention time of the standard substances using HPLC and characteristic fragment ions of LC-MS/MS., Practical Application: A method of getting health care products limonoids from fruit processing by-products segments membrane of pomelo., (© 2014 Institute of Food Technologists®)

Plant endophytic microbial communities consist of many latent plant pathogens and, also, many pathogen-related species with reduced virulence. Though with a long history of co-evolution, the diversity and composition of the endophytic mycobiota, especially the pathogen-related fungal groups, has been under-investigated in Citrus (C.). Based on the amplicon sequencing of fungal internal transcribed spacer (ITS), the leaf endophytic mycobiota were profiled on citrus varieties from different citrus-producing regions. The pomelo variety shared significantly distinctive leaf mycobiota when compared to the mandarin and sweet orange; these conform to their host genetic relationships. In addition, a data set of 241 citrus-related fungi, including 171 (71%) pathogens and potential pathogens, was summarized from previous studies. Under the criteria of local BLAST (covered ITS nucleotide ≥ 150 bp, sequence identity ≥ 99%), a total of 935 fungal operational taxonomic units (OTUs) were assigned to 62 pathogen-related fungal groups, representing 14.9% of the relative abundance in the whole community. Of which, the top groups consisted of Colletotrichum gloeosporioides (mean relative abundance, 4.3%), Co. citricola and Co. karstii (2.7%), Zasmidium citri-griseum (2.4%), and Z. fructigenum (1.4%). At the genus level, the ratio of the pathogen-related fungal groups in 64% of fungal genera (16 out of 25) exceeded 50%, which are the solely or mainly occurring fungi of their genus in citrus. Our study suggests that the leaf endophytic compartment may be an important place for the growth of latent pathogens. [ABSTRACT FROM AUTHOR]

Dwarfing is a pivotal agronomic trait affecting both yield and quality. Citrus species exhibit substantial variation in plant height, among which internode length is a core element. However, the molecular mechanism governing internode elongation remains unclear. Here, we unveiled that the transcriptional cascade consisting of B‐BOX DOMAIN PROTEIN 22 (BBX22) and ELONGATED HYPOCOTYL 5 (HY5) finely tunes plant height and internode elongation in citrus. Loss‐of‐function mutations of BBX22 in an early‐flowering citrus (Citrus hindsii "SJG") promoted internode elongation and reduced pigment accumulation, whereas ectopic expression of BBX22 in SJG, sweet orange (C. sinensis), pomelo (C. maxima) or heterologous expression of BBX22 in tomato (Solanum lycopersicum) significantly decreased internode length. Furthermore, exogenous application of gibberellin A3 (GA3) rescued the shortened internode and dwarf phenotype caused by BBX22 overexpression. Additional experiments revealed that BBX22 played a dual role in regulation internode elongation and pigmentation in citrus. On the one hand, it directly bound to and activated the expression of HY5, GA metabolism gene (GA2 OXIDASE 8, GA2ox8), carotenoid biosynthesis gene (PHYTOENE SYNTHASE 1, PSY1) and anthocyanin regulatory gene (Ruby1, a MYB DOMAIN PROTEIN). On the other hand, it acted as a cofactor of HY5, enhancing the ability of HY5 to regulate target genes expression. Together, our results reveal the critical role of the transcriptional cascade consisting of BBX22 and HY5 in controlling internode elongation and pigment accumulation in citrus. Unraveling the crosstalk regulatory mechanism between internode elongation and fruit pigmentation provides key genes for breeding of novel types with both dwarf and health‐beneficial fortification in citrus. [ABSTRACT FROM AUTHOR]

In the framework of our studies on Citrus cultivars in Greece, the chemical composition of the essential oils (EOs) from the peels and leaves of orange, pummelo, and tangelo (mandarin × grapefruit hybrid) cultivated in Greece have been studied. All EOs have been analyzed through GC-MS, and a total of 47 and 87 metabolites were identified in the peels and leaves, respectively. These metabolites are classified into the chemical groups of terpenes, alcohols, aldehydes, esters, ketones, and organic acids. Limonene was the most abundant compound in the peel EOs. Moreover, bioactive polymethoxyflavones (PMFs) were isolated and structurally determined from the peels of orange and tangelo, highlighting them as a good potential source of natural PMFs. All EOs were evaluated for their antimicrobial activity against nine human pathogenic microorganisms (six bacteria and three fungi), showing an interesting profile. The EOs from the peels of all Citrus species exhibited a stronger antimicrobial activity compared to those from the leaves. The susceptibility of the assayed Gram-positive bacteria was observed to be greater than that of Gram-negative bacteria, while the fungi were also relatively less resistant than bacteria. The rootstock choice did not influence the EO profile of the fruit peel but exerted an influence on the chemical profile of the leaves. [ABSTRACT FROM AUTHOR]

Self-incompatibility (SI) is a crucial mechanism that prevents self-fertilization and inbreeding in flowering plants. Citrus exhibits SI regulated by a polymorphic S -locus containing an S-RNase gene and multiple S -locus F-box (SLF) genes. It has been documented that S-RNase functions as the pistil S determinant, but there is no direct evidence that the SLF genes closely linked with S-RNase function as pollen S determinants in Citrus. This study assembled the genomes of two pummelo (Citrus grandis) plants, obtained three novel complete and well-annotated S -haplotypes, and isolated 36 SLF or SLF-like alleles on the S -loci. Phylogenetic analysis of 138 SLFs revealed that the SLF genes were classified into 12 types, including six types with divergent or missing alleles. Furthermore, transformation experiments verified that the conserved S6-SLF7a protein can lead to the transition of SI to self-compatibility by recognizing non-self S8-RNase in 'Mini-Citrus' plants (S 7 S 8 and S 8 S 29 , Fortunella hindsii), a model plant for citrus gene function studies. In vitro assays demonstrated interactions between SLFs of different S haplotypes and the Skp1–Cullin1–F-box subunit CgSSK1 protein. This study provides direct evidence that SLF controls the pollen function in Citrus , demonstrating its role in the 'non-self recognition' SI system. [ABSTRACT FROM AUTHOR]

Citrus peels are rich in flavonoids, and some valuable flavonoids with health benefits, such as polymethoxyflavones (PMFs), are found almost exclusively in citrus peels. While the peels usually regarded as by-product, leading to source waste. As a traditional method, drying is helpful to increase added-value of peels which can be used as medicine. However, the variations in variety and quantity of flavonoids during drying processes of citrus peel remain unknown. In this study, Guanxi honey pomelo peel investigated the effect of different drying methods on flavonoids content in citrus peels. Five drying techniques, namely, freeze-drying (FD) and hot air drying (HAD) at 30 °C, 50 °C, 70 °C and 90 °C were used employed for drying the pomelo peels and HPLC-Q-TOF-MS analysis identified 39 flavonoids changes in flavonoids across samples. FD proved to better preserve most glycosidic flavonoids. Flavonoid aglycones could be better preserved in samples of HAD at 30 ℃, 50 ℃ HAD and 90 ℃ HAD. Specifically, HAD at 30 ℃ and 50 ℃ HAD is beneficial for obtaining more valued polymethoxyflavones such as 5-hydroxy-6,7,4′-trimethoxyflavone, 5,7,8,4′-tetramethoxyflavone and 3,5,6,7,8,3′,4′-heptamethoxyflavone. The 90℃ HAD resulted in the highest content of naringenin and 5,7,8,4′-tetramethoxyflavanone. This study demonstrated the transformation characteristics of flavonoids in pomelo peel under varying drying conditions, providing benefits for comprehensive utilization of pomelo peel in extracting valued-added flavonoids. [ABSTRACT FROM AUTHOR]

The citrus cultivar 'Local Juhong', which has historically been used as a traditional Chinese medicinal material, originated in Yuanjiang County, Hunan Province.Its parental type and genetic background are indistinct as of yet. Morphological observation shows that 'Local Juhong' has a slight oblateness in fruit shape, a relatively smooth pericarp, a fine and slightly raised oil vacuole, and an inward concave at the blossom end. The tree form and fruit and leaf morphology of 'Local Juhong' are similar to those of 'Huangpi' sour orange. To reveal the genetic background of 'Local Juhong', 21 citrus accessions were evaluated using nuclear and chloroplast SSR markers and whole-genome SNP information. 'Local Juhong' was grouped with mandarins and sub-grouped with 'Miyagawa Wase' and 'Yanxi Wanlu' in a nuclear SSR analysis, which indicated that its pollen parent might be mandarins. It was closely clustered with orange and pummelo in the chloroplast SSR analysis. The genomic sequence similarity rate of 'Local Juhong' with mandarin and pummelo heterozygosity was 70.88%; the main part was the heterozygosity, except for the unknown (19.66%), mandarin (8.73%), and pummelo (3.9%) parts. Thus, 'Local Juhong' may be an F1 hybrid with pummelo as the female parent and mandarin as the male parent, sharing sisterhood with 'Huangpi' sour orange. [ABSTRACT FROM AUTHOR]

Citrus canker disease affects citrus production. This disease is caused by Xanthomonas citri subsp. citri (Xcc). Previous studies confirmed that during Xcc infection, PthA4, a transcriptional activator like effector (TALE), is translocated from the pathogen to host plant cells. PthA4 binds to the effector binding elements (EBEs) in the promoter region of canker susceptibility gene LOB1 (EBEPthA4-LOBP) to activate its expression and subsequently cause canker symptoms. Previously, the Cas12a/CBE co-editing method was employed to disrupt EBEPthA4-LOBP of pummelo, which is highly homozygous. However, most commercial citrus cultivars are heterozygous hybrids and more difficult to generate homozygous/biallelic mutants. Here, we employed Cas12a/CBE co-editing method to edit EBEPthA4-LOBP of Hamlin (Citrus sinensis), a commercial heterozygous hybrid citrus cultivar grown worldwide. Binary vector GFPp1380N-ttLbCas12a:LOBP1-mPBE:ALS2:ALS1 was constructed and shown to be functional via Xcc-facilitated agroinfiltration in Hamlin leaves. This construct allows the selection of transgene-free regenerants via GFP, edits ALS to generate chlorsulfuron-resistant regenerants as a selection marker for genome editing resulting from transient expression of the T-DNA via nCas9-mPBE:ALS2:ALS1, and edits gene(s) of interest (i.e., EBEPthA4-LOBP in this study) through ttLbCas12a, thus creating transgene-free citrus. Totally, 77 plantlets were produced. Among them, 8 plantlets were transgenic plants (#HamGFP1 - #HamGFP8), 4 plantlets were transgene-free (#HamNoGFP1 - #HamNoGFP4), and the rest were wild type. Among 4 transgene-free plantlets, three lines (#HamNoGFP1, #HamNoGFP2 and #HamNoGFP3) contained biallelic mutations in EBEpthA4, and one line (#HamNoGFP 4) had homozygous mutations in EBEpthA4. We achieved 5.2% transgene-free homozygous/biallelic mutation efficiency for EBEPthA4-LOBP in C. sinensis cv. Hamlin, compared to 1.9% mutation efficiency for pummelo in a previous study. Importantly, the four transgenefree plantlets and 3 transgenic plantlets that survived were resistant against citrus canker. Taken together, Cas12a/CBE co-editing method has been successfully used to generate transgene-free canker-resistant C. sinensis cv. Hamlin in the T0 generation via biallelic/homozygous editing of EBEpthA4 of the canker susceptibility gene LOB1. [ABSTRACT FROM AUTHOR]

Naringin is a flavonoid found primarily in citrus species with especially high concentrations being present in grapefruit (Citrus paradisi), bitter orange (Citrus aurantium), and pomelo (Citrus grandis). Because of its many positive effects on human health, naringin has been the focus of increasing attention in recent years. Recently, conventional extraction methods have been commonly replaced with unconventional methods, such as ultrasound-assisted extraction (UAE) and other, more eco-friendly extraction methods requiring little-to-no environmentally harmful solvents or significantly less energy. Naringin analysis is most commonly done via high-performance liquid chromatography (HPLC), and ultrahigh-performance liquid chromatography (UHPLC) coupled with a mass spectrometer (MS) or a photodiode array (DAD) detector. The aim of this review is to provide an overview of recent trends developments in the extraction, sample preparation, and liquid chromatographic analysis of the compound originating from citrus fruits or their products. [ABSTRACT FROM AUTHOR]

Introduction: Obesity can lead to death with associated high-risk diseases such as cardiovascular disease, diabetes, hypertension, stroke and cancer. Obesity results from an excessive dietary fat intake. Pancreatic lipase (PL) is an enzyme that plays a major role in hydrolyzing fats into monoacylglycerol and fatty acids that can be absorbed into the small intestine. One of the strategies to treat obesity is by reducing fat absorption via PL inhibition. This study aims to search for potential PL inhibitors from selected Malaysian plants capable of reducing fat absorption. Methods: Potential PL inhibitors were virtually screened using AutoDock Vina against reported phytochemical compounds from the peels, fruits and leaves of five selected citrus plants namely Citrus aurantifolia (C. aurantifolia), C. grandis, C. medica, C. hystrix and C. microcarpa. Results: The results were classified based on the free energy of binding into three groups: high, moderate, and low inhibition. Eight compounds exhibited high activity against PL. Citrus grandis contributed the highest number of compounds, followed by C. medica, C. microcarpa, C. aurantifolia, and C. hystrix. To validate these findings, 15 methanolic extracts from various parts of these citrus plants were subjected to in vitro bioassays. Notably, the fruit extract of C. medica demonstrated the most potent PL inhibition at 62.59%, possibly due to the presence of diosmetin-6-C-glucoside. Conclusions: In conclusion, virtual screening of small molecules derived from selected citrus plants offers valuable insights into molecular docking and C. medica emerges as a potential anti-obesity plant. [ABSTRACT FROM AUTHOR]

Citrus polyploidy is associated with a wide range of morphological, genetic, and physiological changes that are often advantageous for breeding. Citrus triploid hybrids are very interesting as new seedless varieties. However, tetraploid rootstocks promote adaptation to different abiotic stresses and promote resilience. Triploid and tetraploid hybrids can be obtained through sexual hybridizations using tetraploid parents (2x × 4x, 4x × 2x, or 4x × 4x), but more knowledge is needed about the inheritance pattern of tetraploid parents to optimize the efficiency of triploid varieties and tetraploid rootstock breeding strategies. In this work, we have analyzed the inheritance pattern of three tetraploid genotypes: ‘Chandler’ pummelo (Citrus maxima) and ‘Cleopatra’ mandarin (Citrus reticulata), which represent two clear examples of autotetraploid plants constituted by the genome of a single species, and the ‘Sevillano’ sour orange, which is an allotetraploid interspecific hybrid between C. maxima and C. reticulata. Polymorphic simple sequence repeat (SSR) and single-nucleotide polymorphism (SNP) markers were used to estimate parental heterozygosity restitution, and allele frequencies for centromeric loci were used to calculate the preferential pairing rate related to the proportion of disomic and tetrasomic segregation. The tetraploid pummelo and mandarin displayed tetrasomic segregation. Sour orange evidenced a clear intermediate inheritance for five of the nine chromosomes (1, 2, 5, 7, and 8), a slight tendency toward tetrasomic inheritance on chromosome 3, and intermediate inheritance with a tendency toward disomy for chromosomes 4, 6, and 9. These results indicate that the interspecific versus intraspecific phylogenomic origin affects preferential pairing and, therefore, the inheritance patterns. Despite its high level of heterozygosity, the important preferential chromosome pairing observed in sour orange results in a limited diversity of the genotypic variability of its diploid gametes, and consequently, a large part of the genetic value of the original diploid sour orange is transferred to the tetraploid progenies. [ABSTRACT FROM AUTHOR]

The article discusses four new citrus rootstock cultivars, US SuperSour 2, 3, 4, and 5, released by the US Department of Agriculture between 2018 and 2023. Topics include the rootstocks' origin, genetic characteristics, field performance, and their positive impact on fruit yield, preharvest fruit drop, and fruit quality in HLB-endemic environments.

The assessment of the optimum harvesting stage is a prerequisite to evaluating the performance of new citrus genotypes. The intrinsic and extrinsic fruit quality traits of citrus fruits change throughout their developmental process; therefore, to ensure the highest quality, the fruit must be harvested at an appropriate stage of maturity. The biochemical changes in terms of total soluble solids (TSS), titratable acidity (TA), TSS/TA ratio, BrimA (Brix minus acidity), and ascorbic acid, in addition to the organoleptic acceptability of 16 new interspecific citrus hybrids, were evaluated in New Delhi (India) during the H1-H8 harvesting stage at 15-day intervals to standardize the optimum harvesting stage. The TA and ascorbic acid content were at a maximum level during the early harvesting stage and declined with time, reaching the minimum level in the last harvesting stage. The TSS, TSS/TA ratio, and BrimA values were found to have an increasing trend up to the last stage in most of the hybrids. The juice content shows an inclining trend during the initial harvesting observations, followed by stable juice content and then a decline. The BrimA was found to be a better predictor for consumer acceptability compared to the traditional maturity index TSS/TA ratio and, thus, harvesting maturity. Specific TSS, TA, and BrimA values, in addition to the juice percentage and ascorbic acid content, corresponding to the highest hedonic score, were judged as the optimum harvesting stage indicators for an individual hybrid genotype. Among the interspecific hybrids, SCSH-9-10/12, SCSH-11-15/12, and SCSH-17-19/13 were found to be superior, having better juice acceptability organoleptic scores (≥6.0) and higher juice content (≥40%). Principal component analysis based on fruit physico-chemical traits could be able to distinguish the optimum maturity stage in all of the citrus genotypes. [ABSTRACT FROM AUTHOR]

• Chloroplast genome of 'Zangju' had one less protein-coding gene (rpl22) than 'Tuju'. • There were high commonality of codons and a significant AT preference in chloroplast genomes of the two citrus varieties. • The chloroplast genomes of different citrus species could share one haplotype. • Citrus species had complex lineage relationships and extensive hybridization. Citrus plants, comprising some of the most widely cultivated fruit crops worldwide, have great research value. We assembled and annotated the chloroplast genomes of two local important citrus varieties of China, 'Tuju' and 'Zangju', and comparatively analyzed their sequences. The full lengths chloroplast genomes of 'Tuju' and 'Zangju' were 160,121 and 160,694 bp, respectively. Both featured a quadripartite structure with two copies of a large inverted repeat (IR) separated by small (SSC) and large (LSC) single-copy regions. 'Tuju' chloroplast genome contained 134 genes. 'Zangju' had one less protein-coding gene (rpl22) than 'Tuju'. We also found 27 and 21 optimal codons, all of which ended with A or U, for chloroplast protein-coding genes of 'Tuju' and 'Zangju', respectively. There were 32 haplotypes obtained from 43 citrus chloroplast genomes, some different species or cultivars could share one haplotype. Of them, 'Tuju', one individual of Citrus limon , one individual of Citrus maxima and Citrus platymamma shared one haplotype, which implied they had the same maternal origin. The phylogenetic trees supported that all haplotypes could be divided five groups, while haplotype network analysis tended to get three groups. Our study reveals the complex lineage relationship of citrus plants at a certain level, and provides a valuable reference tool for future research on citrus plants. [ABSTRACT FROM AUTHOR]

Simple Summary: The orange spiny whitefly, Aleurocanthus spiniferus, has invaded Greece and expanded its distribution in other countries in the European Union since 2008. It is a polyphagous pest that includes several highly important crop plants, such as citrus. Damage symptoms and effects on plants are identical to those of the citrus blackfly, Aleurocanthus woglumi (both Hemiptera: Aleyrodidae). The species also share a complex of natural enemies that were successfully introduced to Hawaii during 1974–1998. A short expedition to the islands of Oahu, Hawaii, and Kauai was conducted to retrieve the prominent natural enemies for introduction into Greece. Hawaii was chosen because it does not have citrus diseases and because of the existence of connections to facilitate research and export permits. Infested leaves were shipped to a quarantine facility in Greece for parasitoid emergence and evaluation. The identity of emerged parasitoids and host testing on the orange-spiny whitefly Greece strain were conducted. Only one parasitoid was abundant, characterized using molecular analysis as Encarsis perplexa. A summary of infestation records, parasitism rates, and localities on the Hawaiian Islands has been reported here for the first time since the release of parasitoids. Results showed that the infestations of citrus trees were minimal on the islands of Hawaii and Oahu, primarily on pummelo and sweet orange. Citrus whiteflies were not detected on the island of Kauai during this survey. E. perplexa had parasitism rates ranging from 0 to 28% on the island of Hawaii and 11 to 65% on the island of Oahu. A starter colony of the parasitoids has been colonized in the Greece Quarantine Facility for evaluation. This was the first field survey of Hawaii since the introduction and release of citrus whitefly natural enemies. Further surveys should be repeated in different countries to eliminate the risk of disease introduction. Whitefly species of Aleurocanthus spiniferus (Quaintance) and A. woglumi Ashby (Hemiptera: Aleyrodidae) are serious pests of citrus and other important fruit crops. The problem of citrus has initiated the successful introduction of several natural enemies for biocontrol programs in Hawaii and many other countries. Here, we summarized the history of infestation and biocontrol efforts of the two whiteflies in Hawaii for possible parasitoid importation into Greece. Two Platygasteridae (Amitus hesperidum Silvestri, A. spiniferus (Brethes), and three Aphelinidae (Encarsia clypealis (Silvestri), E. smithi (Silvestri), E. perplexa Huang, and Polaszek) were released in Hawaii for biocontrol of the citrus whiteflies during the period 1974–1999. The aphelinid Cales noacki Howard, purposely released for Aleurothrixus flococcus (Maskell) in 1982, was also reported to attack other whiteflies, including Aleurocanthus species, on citrus. An additional aphelinid parasitoid, Encarsia nipponica Silvestri, native to Japan and China, was accidentally introduced and found to attack both citrus whiteflies on the islands. Since the colonization of introduced parasitoids in infested fields on four Hawaiian Islands, no survey has been conducted to evaluate their potential impact. We conducted two short surveys during September–November 2022 on the islands of Kauai, Hawaii, and Oahu to introduce the dominant parasitoids to Greece for the biocontrol of A. spiniferus. Results showed that the infestation level was very low on Kauai, Hawaii, and Oahu Islands, with a mean infestation level range of 1.4–3.1 on Hawaii and Oahu Islands, mostly on pummelo and sweet orange, with no detection on the island of Kauai. The dominant parasitoid was characterized as Encarsia perplexa, using molecular analysis. Its parasitism rates ranged from 0 to 28% on the island of Hawaii and 11 to 65% on the island of Oahu. Emerged parasitoids have been reared in Greece for evaluation. This was the first field survey of Hawaii since the introduction and release of citrus whitefly natural enemies. [ABSTRACT FROM AUTHOR]

Citrus species are prone to suffer from copper (Cu) toxicity because of improper application of Cu-based agrochemicals. Copper immobilization mediated by pectin methylesterase (PME) in the root cell wall (CW) is effective for Cu detoxification. However, the underlying mechanisms of the structural modification and stress responses of citrus root CW pectin to Cu toxicity have been less discussed. In the present study, seedlings of 'Shatian pummelo' (Citrus grandis L. Osbeck) and 'Xuegan' (Citrus sinensis L. Osbeck), which differ in Cu tolerance, were irrigated with nutrient solution containing 0.5 (as control), 100, 300 or 500 μM Cu for 18 weeks in sandy culture or 24 h in hydroponics. At the end of treatments in the 18-week sandy culture, Cu toxicity on CW pectin content, Cu distribution, degree of pectin methylesterification (DPM) and the PME enzyme activity were discussed. At the genome-wide level, PME gene family was identified from the two citrus species, and qRT-PCR array of citrus PMEs under control and 300 μM Cu stress for 18 weeks were performed to screen the Cu-responsive PME genes. Moreover, the candidate genes that responded to Cu toxicity were further examined within 24 h. The results showed that Cu toxicity increased the root CW pectin content. The root CW pectin under Cu toxicity was remodeled by upregulation of the expression of the Cu-responsive PME genes followed by increasing PME activity, which mainly promoted low methylesterased pectin level and the Cu content on root CW pectin. Compared with C. sinensis , C. grandis root CW had a lower DPM and higher Cu content on the Cu-stressed root CW pectin, contributing to its higher Cu tolerance. Our present study provided theoretical evidence for root CW pectin remodeling in response to Cu toxicity of citrus species. [ABSTRACT FROM AUTHOR]

The assessment of genetic diversity is crucial in citrus improvement programs that represents the relationship among genotypes, thus determining an effective plant breeding program. A molecular assessment of 52 collected citrus accessions based on ISSR and SSR was conducted at the ICSFRI in 2020. Based on 4 ISSR primers and 3 SSR primers, the citrus genotypes were grouped into 6 major clusters. Cluster I has the largest 25 members, while Cluster II, III, IV, V and VI have 5, 2, 2, 4 and 13 accession members, respectively. Members of Cluster I are the majority in the mandarin type with spheroids fruit shape with truncate on the fruit top. Cluster II contains citrus accessions from naturally occurring hybrids, while orange accession members of Cluster III are originally grown in different climates. Cluster IV and V members are connected to a common ancestor, Citrus aurantifolia and Citrus limonia. At the same time, Cluster VI is a pumelo group that contains members of Citrus maxima. Clustering based on molecular markers (ISSR and SSR) resulting in this study is useful in citrus breeding programs in Indonesia and other countries. The genetic distance of the parents affects the heterosis effect of the progeny. [ABSTRACT FROM AUTHOR]

Citrus fruits are cultivated around the world, and they face drought stress frequently during their growth and development. Previous studies showed that citrus plants biosynthesized flavonoid compounds in response to abiotic stress. In this study, we have quantified 37 flavonoid compounds from the leaves of three distinct citrus species including sour orange (drought-tolerant), pummelo 'Majia you pummelo' (drought-sensitive), and lemon (drought-sensitive). The 37 flavonoids consisted of 12 flavones, 10 flavonols, 6 flavanones, 5 isoflavanones, and 1 each for chalcone, flavanol, flavanonol, and flavone glycoside. Drought stress differentially altered the flavonoid metabolism in drought-tolerant and drought-sensitive citrus species. The kaempferol 3-neohesperidoside was 17-fold higher in sour orange (124.41 nmol/L) after 18 days of drought stress than lemon (7.33 nmol/L). In sour orange, neohesperidin (69.49 nmol/L) was 1,407- and 37-fold higher than pummelo and lemon, respectively. In sour orange, some flavonoids were significantly increased, such as vitexin, neohesperidin, cynaroside, hyperoside, genistin, kaempferol 3-neohesperidoside, eriocitrin, and luteolin, in response to drought stress, whereas in lemon, these flavonoids were significantly decreased or not altered significantly in response to drought stress. Moreover, the total contents of flavonoids and antioxidant activity were increased in sour orange as compared with pummelo and lemon. The genes associated with flavonoid biosynthesis (PAL, CHI, FLS, GT1, F3H, F3'M, C4H, 4CL, FLS, FG2, FG3, and CYP81E1) were more highly expressed in sour orange leaves than in pummelo and lemon after drought stress. These outcomes showed that pummelo and lemon failed to biosynthesize antioxidant flavonoids to cope with the prolonged drought stress, whereas the sour orange biosynthesized fortified flavonoid compounds with increased antioxidant activity to detoxify the harmful effects of reactive oxygen species produced during drought stress. [ABSTRACT FROM AUTHOR]

Main conclusion: CgPG21 is mainly located in the cell wall, participates in the intercellular layer degradation of the cell wall during the formation of secretory cavity in the intercellular space-forming and lumen-expanding stages. The secretory cavity is a common structure in Citrus plants and is the main site for synthesis and accumulation of medicinal ingredients. The secretory cavity is formed in lysogenesis, when epithelial cells enter a process of programmed cell death. Pectinases are known to be involved in degradation of the cell wall during the cytolysis of secretory cavity cells, but the changes in cell structure, the dynamic characteristics of cell wall polysaccharides and the related genes regulating cell wall degradation are unclear. In this study, electron microscopy and cell wall polysaccharide-labeling techniques were used to study the main characteristics of cell wall degradation of the secreting cavity of Citrus grandis 'Tomentosa' fruits. At the same time, the full CDS length of the pectinase gene CgPG21 was cloned, encoding a protein composed of 480 amino acids. CgPG21 is mainly located in the cell wall, participates in the degradation of the intercellular layer of the cell wall during the development of the secretory cavity, and plays an important role in the formation of the secretory cavity in the intercellular space-forming and lumen-expanding stages. With the development of secretory cavity, the cell wall polysaccharides of epithelial cells gradually degrade. CgPG21 is mainly involved in the intercellular layer degradation. [ABSTRACT FROM AUTHOR]

Citrus species among the most important and widely consumed fruit in the world due to Vitamin C, essential oil glands, and flavonoids. Highly variable simple sequence repeats (SSR) markers are one of the most informative and versatile molecular markers used in perennial tree genetic research. SSR survey of Citrus sinensis and Citrus maxima were identified perfect SSRs spanning nine chromosomes. Furthermore, we categorized all SSR motifs into three major classes based on their tract lengths. We designed and validated a class I SSRs in the C. sinensis and C. maxima genome through electronic polymerase chain reaction (ePCR) and found 83.89% in C. sinensis and 78.52% in C. maxima SSRs producing a single amplicon. Then, we selected extremely variable SSRs (> 40 nt) from the ePCR-verified class I SSRs and in silico validated across seven draft genomes of citrus, which provided us a subset of 84.74% in C. sinensis and 77.53% in C. maxima highly polymorphic SSRs. Out of these, 129 primers were validated on 24 citrus genotypes through wet-lab experiment. We found 127 (98.45%) polymorphic HvSSRs on 24 genotypes. The utility of the developed HvSSRs was demonstrated by analysing genetic diversity of 181 citrus genotypes using 17 HvSSRs spanning nine citrus chromosomes and were divided into 11 main groups through 17 HvSSRs. These chromosome-specific SSRs will serve as a powerful genomic tool used for future QTL mapping, molecular breeding, investigation of population genetic diversity, comparative mapping, and evolutionary studies among citrus and other relative genera/species. [ABSTRACT FROM AUTHOR]

The global food industry and especially fruit juice production generates millions of tons of organic waste annually. Citrus waste, also known as citrus pulp оr citrus pomace, is a residue obtained during various citrus juices production. This by-product has the potential to become an excellent source of essential nutrients in animal feeding. In the current study, the chemical and mineral composition were determined in the citrus waste by Orange (Citrus sinensis), Lemon (Citrus limon), Red grapefruit (Citrus paradisi), Mandarin (Citrus reticulata), Lime (Citrus aurantifolia), Pomelo (Citrus maxima). Waste products are derived from the production factory of freshly squeezed fruit and vegetable juices located in the village of Musachevo, Western Bulgaria. For all citrus waste, the following indicators were determined: dry matter (DM), moisture (RH), crude protein (CP), crude fibre (CF), crude ash (CA), ether extract (EE), manganese (Mn), zinc (Zn), magnesium (Mg), calcium (Ca), phosphorus (P), sodium (Na), potassium (K). The mineral content was determined by Atomic Absorption Spectrophotometer. Their chemical and mineral composition analyses showed differences in the distribution of nutrients and minerals. The data obtained from the conducted analyses showed that citrus pulp could successfully replace some of the main raw materials in the animal’s ration, as it is a source of essential nutrients for it. [ABSTRACT FROM AUTHOR]

Meloidogyne enterolobii Yang & Eisenback, 1983 is amongst the most aggressive root-knot nematodes, causing significant annual losses worldwide to many crops and emerging in many countries recently. Although plants belonging to the citrus family such as grapefruit and citrus have been reported as non-hosts or poor hosts for M. enterolobii, our study recorded the heavy infection of a root-knot nematode that resembles M. enterolobii on pomelo, a species in the citrus family. The molecular data of D2-D3 of 28S rRNA region, morphometrics, and morphological features of second-stage juveniles, males, and females in the present study have confirmed that the root-knot nematode recovered from pomelo in Vietnam belongs to M. enterolobii. To the best of our knowledge, this represents the first report of M. enterolobii infecting pomelo, providing new insight into the host status of this important pest. [ABSTRACT FROM AUTHOR]

Interstocks have been used in fruit tree cultivation to regulate tree size and improve fruit production and quality. In this study, several Huanglongbing (HLB)-tolerant open-pollinated pummelo interstock candidates were evaluated as interstocks between the Swingle rootstock and the 'Valencia' scion, with Swingle serving as the control interstock. After 5 years in the field, most trees did not exhibit visual HLB symptoms, although the trees were infected with HLB, and the CaLas Ct values in the 'Valencia' leaves of the different interstock treatments ranged between 25.88 and 27.82. Although the foliar chlorophyll content among the interstock treatments was not highly significant (p-value = 0.0313), the foliar starch content was significantly different (p-value = 0.0018). 'Valencia' grafted onto 5-1-99-3 and HBJL-4 interstocks (both open pollinated seedlings of the Hirado Buntan pummelo) exhibited the highest total phenolic compound (TPC) levels (46.44 and 46.36 mg gallic acid g−1 FW). Transcripts of CsPR1 and CsPR2, two pathogenesis-related (PR) genes, were upregulated in 'Valencia' grafted onto open pollinated seedling selections of the red shaddock pummelo, Liang Ping Yau pummelo, and Hirado Buntan pummelo compared with 'Valencia' grafted onto Swingle. All interstocks influenced the tree growth rate and improved canopy volume in the field compared to the control trees without any interstocks (p-value = 0.0085). The 5-4-99-7 (red shaddock pummelo) and 8-1-99-1B (Liang Ping Yau pummelo) interstock trees had the highest canopy volume among all the treatments. We propose, based on our current results, that HLB-tolerant citrus accessions, when judiciously used as interstocks, may enhance plant defense and provide increased HLB tolerance to susceptible scions. [ABSTRACT FROM AUTHOR]

Aluminum (Al) toxicity is one of the most serious hazards of soil acidification, which limits root formation and hinders crop growth. Soil acidification in orchards has been widely reported. However, there is little information about the effect of Al3+ on citrus roots in acidified red soil. Taking pomelo (Citrus grandis), the main citrus variety in Southeast China, as an example, soil surveys were conducted to analyze the status and characteristics of acidification in pomelo orchards. Subsequently, we explored whether optimized fertilization and liming can effectively reduce Al toxicity in roots and increase yield by three treatments, including farmer fertilization practice (FFP), NPK optimization (OPT), and OPT combined with lime (OPT+L). The results showed that (1) rapid soil acidification occurred in pomelo orchards in the past 40 years (with a decrease of 0.81 units). The severity of soil acidification increases with orchard age. In addition, the soil pH and base saturation (BS) at the drip line (DL; i.e., fertilization site) were the lowest, while the concentration of exchangeable acid (Ex.Acid) and exchangeable Al (Ex.Al), and the ratio of Ex.Al to cation exchange capacity (Ex.Al%) was highest compared to other locations away from DL. Random forest analysis indicated Ex.Al was the most important factor to reflect soil acidification. (2) Under the OPT+L treatment, the concentrations of soil Ex.Acid and Ex.Al decreased, and BS increased, which markedly reduced the Al3+ concentration in the roots and promoted root growth. OPT+L significantly decreased the Al concentrations in soils (by 71.3%) and roots (by 47.8%) but increased root activity, root length, root tips and root surface area by 119.2%, 80.3%, 124.6% and 136.6%, respectively. In addition, structural equation modeling further proved that increasing soil pH and BS while decreasing Ex.Al was beneficial to citrus production in acidic soil, and optimized fertilization and lime application are necessary. [ABSTRACT FROM AUTHOR]

'Aliza' is a new pomelo × mandarin hybrid (Citrus maxima, cv. Red Chandler × Citrus reticulata, cv. Ora) developed by the Israeli citrus breeding program at the Volcani Institute. Here, we aimed to characterize the quality and flavor of 'Aliza' fruit as compared to other commercial citrus fruit, specifically pomelo (C. maxima), grapefruit (Citrus paradisi), orange (Citrus sinensis) and mandarin (C. reticulata). 'Aliza' fruits have a similar size as grapefruits, but have a thinner peel and a unique yellowish/golden color. 'Aliza' fruits are completely seedless and have especially high juice contents. They also have a unique, highly preferred flavor, characterized by high sweetness and moderate bitterness and acidity, with strong citrusy and tropical fruity aromas. Sensory analyses conducted with the aid of a trained panel and an electronic tongue revealed that the flavor of 'Aliza' fruits is different from the flavors of other citrus species. Consumer acceptance and preference tests revealed that 'Aliza' fruit are highly appreciated and favored. The aroma volatile profile of 'Aliza' fruit was somewhat similar to those of pomelo and grapefruit, but very different from those of orange and mandarin. Overall, 'Aliza' fruits can be distinguished from other citrus fruits by their unique color, high juice content and exceptional, unique flavor. [ABSTRACT FROM AUTHOR]

Orange (Citrus x aurantium var sinensis) is the most widely consumed citrus fruit, and its essential oil, which is made from the peel, is the most widely used in the food, perfume, and cosmetics industries. This citrus fruit is an interspecific hybrid that would have appeared long before our era and would result from two natural crosses between mandarin and pummelo hybrids. This single initial genotype was multiplied by apomictic reproduction and diversified by mutations to produce hundreds of cultivars selected by men essentially based on phenotypic characteristics of appearance, spread of maturity, and taste. Our study aimed to assess the diversity of essential oil composition and variability in the aroma profile of 43 orange cultivars representing all morphotypes. In agreement with the mutation-based evolution of orange trees, the genetic variability tested with 10 SSR genetic markers was null. The oils from peels and leaves extracted by hydrodistillation were analyzed for composition by GC (FID) and GC/MS and for aroma profile by the CATA (Check All That Apply) method by panelists. Oil yield varied between varieties by a factor of 3 for PEO and a factor of 14 for LEO between maximum and minimum. The composition of the oils was very similar between cultivars and was mainly dominated by limonene (>90%). However, small variations were observed as well as in the aromatic profile, with some varieties clearly distinguishing themselves from the others. This low chemical diversity contrasts with the pomological diversity, suggesting that aromatic variability has never been a selection criterion in orange trees. [ABSTRACT FROM AUTHOR]

Citrus is among the most economically important fruit crops. Its vast species diversity and global production was observed by N.I. Vavilov during his international plant explorations from the early to mid-1900s. Currently, ex situ citrus collections located around the world conserve and protect citrus genetic resources, as revealed in a survey conducted in 2021. Responses were received from 43 collections in 27 countries, of which 35 provided data regarding collection composition, management practices, and security, as well as other information. The six largest citrus collections have between 1000 and 1735 accessions. The largest accession holdings are mandarins and sweet oranges, although all citrus fruit types are maintained: mandarin, sweet orange, lemon, pummelo, grapefruit, hybrids, lime, sour orange, citron, kumquat, papeda, finger lime, and crop wild relatives. Diseases pose significant threats to collections, though some collections are maintained in a clean-plant state as a result of intensive sanitation efforts. National and regional quarantine regulations often limit the export and import of citrus plants or propagative materials, thus limiting the availability of materials at an international level. Resources, both financial and human, are necessary to ensure the long-term safety and security of citrus collections on a global scale. Future efforts to develop citrus genebanking communities will provide opportunities for improved conservation, as well as collaborations and training. [ABSTRACT FROM AUTHOR]

Among Citrus species, the sweet orange (Citrus sinensis (L.) Osbeck) is the most important in terms of production volumes and cultivated areas. Oranges are particularly appreciated for the organoleptic characteristics and the high nutraceutical value of the fruits (thanks especially to their high content of antioxidants). Recent advances in citrus genetic and genomic resources, such as the release of the reference genomes of several sweet orange cultivars, have contributed to (i) understanding the diversification of C. sinensis and its relation with other citrus species, (ii) assessing the molecular mechanisms underlying traits of interest, (iii) identifying and characterizing the candidate genes responsible for important phenotypic traits, and (iv) developing biotechnological methods to incorporate these traits into different citrus genotypes. It has been clarified that all the genetic diversity within the sweet orange species was derived from subsequent mutations starting from a single ancestor and was derived from complex cycles of hybridization and backcrossing between the mandarin (Citrus reticulata Blanco) and the pummelo (Citrus maxima (Burm.) Merr.). This paper provides an overview of the varietal panorama together with a description of the main driving forces in present and future sweet orange breeding. In fact, for the sweet orange, as well as for other citrus species, the release of novel varieties with improved characteristics is being pursued thanks to the employment of conventional and/or innovative (molecular-based) methods. The state of the art methods together with the innovations in genomics and biotechnological tools leading to the so-called new plant breeding technologies were also reviewed and discussed. [ABSTRACT FROM AUTHOR]

Over-applied copper (Cu)-based agrochemicals are toxic to citrus trees. However, less information is available discussing the ultrastructural alterations in Cu-stressed citrus species. In the present study, seedlings of Citrus sinensis and Citrus grandis that differed in Cu-tolerance were sandy-cultured with nutrient solution containing 0.5 µM Cu (as control) or 300 µM Cu (as Cu toxicity) for 18 weeks. At the end of the treatments, the physiological parameters and ultrastructural features of the citrus leaves and roots were analyzed. The results indicate that Cu toxicity significantly decreased the ratio of shoot biomass to dry weight, the Cu translocation factor and the total chlorophyll of two citrus species. The anatomical and ultrastructural alterations verified that excessive Cu resulted in starch granules accumulated in the leaves and roots of the two citrus species. Under Cu toxicity, increased root flocculent precipitate and thickened root cell wall might reduce the Cu translocation from citrus roots to the shoots. Compared with C. sinensis, C. grandis maintained a relatively integral root cellular structure under Cu toxicity, which provided a structural basis for a higher Cu tolerance than C. sinensis. The present results increase our understanding of the physiological and ultrastructural responses to Cu toxicity in citrus species. [ABSTRACT FROM AUTHOR]

'Liuyuezao' (LYZ) pummelo (Citrus maxima) originated from a spontaneous bud sport on a 'Guanxi' (GXB) pummelo tree and was released as a new very earlyseason cultivar. The objective of this study was to present the sensory and nutritional profiles of LYZ fruits, and compare it with other major commercialized pummelo cultivars including GXB, 'Sanhong' (SH) and 'Hongrou' (HR). LYZ had higher contents of organic acids (12.01 mg/g), phenols (669.01 mg/L), vitamin C (75.73 mg/100 mL) and stronger antioxidant capacity (77.65 mg/100 mL) but lower levels of soluble sugars (62.85 mg/g), carotenoids (0.25 mg/L) and flavonoids (46.3 mg/L) when compared to the other pummelos. Moreover, a smaller number (49) andmuch less content (7.63) of fruit volatiles were detected in LYZ than them in GXB, SH and HR. The relatively high levels of fructose (20.6mg/g) and organic acids and low levels of volatile compounds in LYZ mainly contributed to its sweet and mildly sour taste and moderate aroma of pummelo note. LYZ is presented as an alternative pummelo cultivar with the potential for commercialization. [ABSTRACT FROM AUTHOR]

Fertilization is one of the most important aspects during commercial citrus production. A better tradeoff is also required for the fruit quality with the fertilizer reduction and nutrients efficiency. In this study, an expert system was constructed for the citrus fertilization recommendation of mineral nutrients, according to the comprehensive evaluation of fruit quality. The 40 plots of 10-12a Longan pomelo (Citrus Grandis cv. ‘Longan’) orchard were selected in the Modern Agricultural Industrial Park of Longan Pomelo, Guangan City, Sichuan Province, China. The indexes were tracked from 2019 to 2020, including the tree mineral nutrition at the fruit expansion stage (early June), and the fruit quality at the fruit maturity stage (mid-November). The original database was then established. Three algorithms were constructed, including the nutrient criteria generation of high-quality leaf at the fruit expansion stage, the correction fertilization of deviation from the optimum percentage (DOP), according to the standard of “yield quantification, the total quantity control, and staging control”, and the compound fertilizer formula recommendation using the local fertilizer and agricultural materials supply database. Four functions were then achieved, namely, the automatic generation of high-quality leaf nutrient criteria during fruit expansion, the nutritional assessment of citrus orchards, the recommendation of available nutrient formulations, and the recommendation of compound fertilizer formulations. The system was distributed to the growers, government agencies, and system administrators with the different permissions using role-based access control (RBAC). A series of validation experiments were carried out on the nutrient expert system for the citrus fertilization recommendation at the early stage of fruit expansion in 2021. Two circus orchards were selected, where the chemical fertilizer was applied in the Longan Town, whereas, the organic fertilizer was in the Chongwang Town. The average low-, middle-, and high-yield plantations were taken as the system target yields. The effective formula of nutrient correction was used to generate three schemes of recommended fertilization for two orchards, labeled as the RF1, RF2, RF3. The FP control groups were marked as the experience fertilization schemes for the citrus orchards in Longan and Chongwang Town, respectively. The results showed that the RF2 treatments for two orchards performed the best with the average yield of 35.71 t/hm2, particularly serving as the recommended fertilization scheme. Specifically, the RF2 treatment for Longan was reduced by 40.3%, 43.6%, and 1.3% in the nitrogen (N), Kalium (K), and potassium (P) inputs, respectively, compared with the chemical experience fertilization schemes. By contrast, the RF2 treatment for Chongwang was reduced the N, K and P inputs by 27.1%, 30.8%, and 78.8%. Those two RF2 treatments were achieved in the optimal purpose of “Fertilizer reduction”. At the same time, the treatments can be expected to effectively avoid the delays in the fruit coloring and the low overall fruit quality that caused by the excessive and imbalanced chemical fertilization inputs. The low inputs of N and P fertilizers can be alleviated the small fruit sizes and delayed fruit pulp color, due to the empirical organic fertilizer application. Therefore, the nutrient fertilization recommendation system can be promising potential to promote the nutrient correction formula fertilization for commercial citrus industry. [ABSTRACT FROM AUTHOR]

Sweet orange originated from the introgressive hybridizations of pummelo and mandarin resulting in a highly heterozygous genome. How alleles from the two species cooperate in shaping sweet orange phenotypes under distinct circumstances is unknown. Here, we assembled a chromosome-level phased diploid Valencia sweet orange (DVS) genome with over 99.999% base accuracy and 99.2% gene annotation BUSCO completeness. DVS enables allele-level studies for sweet orange and other hybrids between pummelo and mandarin. We first configured an allele-aware transcriptomic profiling pipeline and applied it to 740 sweet orange transcriptomes. On average, 32.5% of genes have a significantly biased allelic expression in the transcriptomes. Different cultivars, transgenic lineages, tissues, development stages, and disease status all impacted allelic expressions and resulted in diversified allelic expression patterns in sweet orange, but particularly citrus Huanglongbing (HLB) shifted the allelic expression of hundreds of genes in leaves and calyx abscission zones. In addition, we detected allelic structural mutations in an HLB-tolerant mutant (T19) and a more sensitive mutant (T78) through long-read sequencing. The irradiation-induced structural mutations mostly involved double-strand breaks, while most spontaneous structural mutations were transposon insertions. In the mutants, most genes with significant allelic expression ratio alterations (≥1.5-fold) were directly affected by those structural mutations. In T19, alleles located at a translocated segment terminal were upregulated, including CsDnaJ, CsHSP17.4B, and CsCEBPZ. Their upregulation is inferred to keep phloem protein homeostasis under the stress from HLB and enable subsequent stress responses observed in T19. DVS will advance allelic level studies in citrus. [ABSTRACT FROM AUTHOR]

Different genetic and environmental factors like altitude, temperature, light radiation, etc. affect the production of phytoconstituents like ascorbic acid, phenol, flavonoid, tannin, etc. So, it is necessary to evaluate phytoconstituents quantitatively and qualitatively because of their different medicinal values. This study is aimed at evaluating and comparing ascorbic acid concentration, total phenol, and flavonoid content in citrus species grown in different places in Western Nepal. For this, fruit collected from Lamjung and Nawalparasi was peeled, and collected juice was extracted with ethanol. Ascorbic acid was estimated using titration with dichlorophenolindophenol dye, and total phenol was estimated using Folin reagent; whereas, flavonoid content was determined by aluminum chloride colorimetric assay. The result showed the maximum ascorbic acid concentration in the fruit juice of Citrus maxima collected from Lamjung, i.e., 2.98 ± 0.161 mg / 100 ml , and the least concentration was recorded on extract of Citrus limon collected from Nawalparasi, i.e., 1.005 ± 0.205 mg / 100 ml. The total phenol content was comparatively higher in Citrus maxima and Citrus aurantifolia collected from Lamjung, i.e., 12.48 ± 0.40 mg GAE/gm, respectively. Flavonoid content was comparatively higher in Citrus maxima collected from Nawalparasi, i.e., 484.466 ± 3.055 mg QE/gm. This study showed a variation in the concentration of chemical constituents between different places in Western Nepal. This might be due to differences in climatic conditions, environmental factors, altitude, temperature, etc. This study helps to reflect the best-suited altitude for commercial cultivation of the citrus species as these phytochemicals have different medicinal values. Also, this study can help the food industry to use an alternative source of synthetic antioxidant such as ascorbic acid, phenol, and flavonoid. And local people will economically benefit by the commercial cultivation of citrus fruits. [ABSTRACT FROM AUTHOR]