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Huanglongbing (HLB) is a fatal citrus disease that is currently threatening citrus varieties worldwide. One putative causative agent, Candidatus Liberibacter asiaticus (CLas), is vectored by Diaphorina citri, known as the Asian citrus psyllid (ACP). Understanding the details of CLas infection in HLB disease has been hindered by its Candidatus nature and the inability to confidently detect it in diseased trees during the asymptomatic stage. To identify early changes in citrus metabolism in response to inoculation of CLas using its natural psyllid vector, leaves from Madam Vinous sweet orange (Citrus sinensis (L.) Osbeck) trees were exposed to CLas-positive ACP or CLas-negative ACP and longitudinally analyzed using transcriptomics (RNA sequencing), proteomics (liquid chromatography-tandem mass spectrometry; data available in Dryad: 10.25338/B83H1Z), and metabolomics (proton nuclear magnetic resonance). At 4 weeks postexposure (wpe) to psyllids, the initial HLB plant response was primarily to the ACP and, to a lesser extent, the presence or absence of CLas. Additionally, analysis of 4, 8, 12, and 16 wpe identified 17 genes and one protein as consistently differentially expressed between leaves exposed to CLas-positive ACP versus CLas-negative ACP. This study informs identification of early detection molecular targets and contributes to a broader understanding of vector-transmitted plant pathogen interactions.

A simple aqueous host:guest sensing array can selectively discriminate between different types of citrus varietal from peel extract samples. It can also distinguish between identical citrus samples at varying stages of ripening. The discrimination effects stem from detection of changes in the terpenoid composition of the peel extracts by the host:guest array, despite the overwhelming excess of a single component, limonene, in each sample. The hosts are insensitive to limonene but bind other monoterpenes strongly, even though they are similar in structure to the major limonene component. This work demonstrates the capability of host:guest arrays in sensing target molecules in environments with the competing agents present at high abundances in the sample matrix.

This study aimed to assess the antioxidant capacity of lemon flavonoid extract Eriomin® (LE) and its impact on cholesterol metabolism in the context of healthy aging. We orally treated 24-month-old male Wistar rats with an LE (40 mg/kg) suspended in 0.3 mL of sunflower oil. At the same time, control groups received an equal volume of sunflower oil (CON) or remained untreated (ICON) daily for 4 weeks. We examined LEs effects on superoxide dismutase and catalase- and glutathione-related enzyme activities, the concentration of lipid peroxides and protein carbonyls, total oxidant status (TOS) and antioxidant status (TAS), and oxidative stress index (OSI) in the liver, jejunum, and ileum. We also measured total cholesterol, its biosynthetic precursors (lanosterol, lathosterol, desmosterol), its degradation products (bile acid precursors) in the serum, liver, jejunum, and ileum, and serum phytosterols (intestinal absorption markers). LE reduced TOS, TAS, and OSI (p < 0.05) compared with control values, indicating its consistent antioxidant action in all examined organs. LE lowered hepatic desmosterol (p < 0.05) while also reducing 7α- and 24-hydroxycholesterol levels in the liver and ileum (p < 0.01). Serum cholesterol, hepatic gene expression, and the immunostaining intensity of CYP7A1 were unchanged. In conclusion, LE exerted non-enzymatic antioxidant effects and reduced cholesterol degradation, reducing its biosynthesis products, thereby maintaining serum cholesterol levels.

The Asian Citrus Psyllid (ACP), Diaphorina citri, is a vector of the pathological bacterium Candidatus Liberibacter asiaticus (CLas), which causes the most devastating disease to the citrus industry worldwide, known as greening or huanglongbing (HLB). Earlier field tests with an acetic acid-based lure in greening-free, Valencia citrus orange groves in California showed promising results. The same type of lures tested in São Paulo, Brazil, showed unsettling results. During the unsuccessful trials, we noticed a relatively large proportion of females in the field, ultimately leading us to test field-collected males and females for Wolbachia and CLas. The results showed high rates of Wolbachia and CLas infection in field populations. We then compared the olfactory responses of laboratory-raised, CLas-free, and CLas-infected males to acetic acid. As previously reported, CLas-uninfected males responded to acetic acid at 1 µg. Surprisingly, CLas-infected males required 50 × higher doses of the putative sex pheromone, thus explaining the failure to capture CLas-infected males in the field. CLas infection was also manifested in electrophysiological responses. Electroantennogram responses from CLas-infected ACP males were significantly higher than those obtained with uninfected males. To the best of our knowledge, this is the first report of a pathogen infection affecting a vectors response to a sex attractant.

Roof rats (Rattus rattus) are an invasive rodent that can cause substantial damage in citrus orchards. Their populations appear to be expanding throughout California, yet little is known about efficacious, cost-effective strategies to manage this invasive pest while minimizing pesticide use. Therefore, we developed two Integrated Pest Management (IPM) programs based on results of recent studies that incorporated observations of roof rat movement patterns, compared monitoring tools, and tested trapping and baiting options. Both IPM programs utilized elevated bait stations containing 0.005% diphacinone-treated oats and trapping, and we compared those programs to a bait-station only approach to determine which strategies were most practical. Initial IPM plots included a combination of elevated bait stations followed by a brief snap-trapping program and a longer-duration trapping program with Goodnature® A24 traps to hopefully keep rat numbers at low levels (Trial 1). Although initial bait applications were effective at reducing rat numbers, populations quickly rebounded within both the bait station only and IPM treatment areas within two-months following the completion of the baiting programs. Additionally, costs for this initial IPM approach were almost five times as much as a bait station approach. Our second IPM strategy (Trial 2) again incorporated an initial bait application period to knock down roof rat populations, followed by the use of trapping tunnels that contained two snap traps to further reduce/maintain rat numbers longer-term. We again observed effective knockdown with bait applications. However, in contrast to Trial 1, we observed substantial success with trapping tunnels at maintaining, and even increasing, overall efficacy within IPM plots, and IPM plots were always more efficacious than bait station only plots. Although the bait station only approach was less costly than the IPM approach used in Trial 2, the cost disparity was substantially less than that for Trial 1, and the cost difference disappeared during subsequent years, indicating long-term cost-effectiveness of this IPM approach. Collectively, the relatively low cost and high efficacy of a management program that incorporates initial bait applications to knock down roof rat populations, followed by a long-term snap-trapping program to maintain low densities, should provide an effective strategy for managing roof rats in citrus orchards.

Rapid advancements in technologies provide various tools to analyze fruit crop genomes to better understand genetic diversity and relationships and aid in breeding. Genome-wide single nucleotide polymorphism (SNP) genotyping arrays offer highly multiplexed assays at a relatively low cost per data point. We report the development and validation of 1.4M SNP Axiom® Citrus HD Genotyping Array (Citrus 15AX 1 and Citrus 15AX 2) and 58K SNP Axiom® Citrus Genotyping Arrays for Citrus and close relatives. SNPs represented were chosen from a citrus variant discovery panel consisting of 41 diverse whole-genome re-sequenced accessions of Citrus and close relatives, including eight progenitor citrus species. SNPs chosen mainly target putative genic regions of the genome and are accurately called in both Citrus and its closely related genera while providing good coverage of the nuclear and chloroplast genomes. Reproducibility of the arrays was nearly 100%, with a large majority of the SNPs classified as the most stringent class of markers, "PolyHighResolution" (PHR) polymorphisms. Concordance between SNP calls in sequence data and array data average 98%. Phylogenies generated with array data were similar to those with comparable sequence data and little affected by 3 to 5% genotyping error. Both arrays are publicly available.

Summary Autophagy is a conserved degradation pathway that regulates the clearance of paternal substrate at the early embryogenesis stage of animals. However, its mode of action is likely different in plants, which can regenerate through apomixis without fertilisation. Somatic embryogenesis (SE) is a unique plant process widely used for plant propagation and germplasm utilisation. Here, we studied citrus as an example and found a higher autophagic activity after SE initiation. Interestingly, amyloplasts were frequently found inside autophagosomes, whereas the inhibition of autophagy blocks amyloplasts/starch degradation and hinders somatic embryo formation. Furthermore, the consumption of storage lipids was faster in autophagy mutants, suggesting lipid metabolism is activated when starch utilisation is blocked. Exogenous application of autophagy‐inducing chemicals (e.g. spermidine) significantly promoted the formation of autophagosomes and increased SE efficiency, indicating a positive correlation between autophagy, energy metabolism, and somatic embryo formation in citrus. Taken together, our study unveils a pathway for the degradation of plant‐specific organelles and provides an effective approach for plant propagation. [ABSTRACT FROM AUTHOR]

In citrus, the synthetic auxin 3,5,6-trichloro-2-pyridyloxyacetic acid (3,5,6-TPA), applied as a foliar spray at a concentration of 15 mg l− 1 during physiological fruitlet abscission, caused additional fruitlet drop and reduced the number of fruits reaching maturity. The effect was much more pronounced at full physiological abscission than after. In this study, this thinning effect was successfully exploited for the first time in sour orange trees grown in an urban environment, reducing harvesting costs by up to almost 40%. This effect is mediated by the leaves, which alter their photosynthetic activity. Our results show a reduction of carbon fixation and sucrose synthesis in the leaf, by 3,5,6-TPA repression of the RbcS, SUS1 and SUSA genes, its transport to the fruit, as shown by the reduced expression of the sucrose transporter genes SUT3 and SUT4, and its hydrolysis in the fruit, mainly by repression of the SUS1 gene expression. Genes involved in auxin homeostasis in the fruit, TRN2 and PIN1, were also repressed. The coordinated repression of all these genes is consistent with the decrease in the fruit cell division rate, as shown by the repression of CYCA1-1 gene, leading to the production of ethylene, which ultimately induces fruitlet abscission. [ABSTRACT FROM AUTHOR]

Citrus bacterial canker (CBC) is resulted from Xanthomonas citri subsp. citri (Xcc) infection and poses a significant threat to citrus production. Glutathione S-transferases (GSTs) are critical in maintaining redox homeostasis in plants, especially in relation to abiotic and biotic stress responses. However, the function of GSTs in resisting CBC remains unclear. Here, citrus glutathione S-transferases were investigated applying a genome-wide approach. In total, 69 CsGSTs belonging to seven classes were identified, and the phylogeny, chromosomal distribution, gene structures and conserved motifs were analyzed. Several CsGSTs responded to Xcc infection, as observed in the upregulation of CsGSTF1 and CsGSTU18 in the CBC-sensitive 'Wanjincheng' variety but not in the resistant 'Kumquat' variety. CsGSTF1 and CsGSTU18 were localized at the cytoplasm. Transient overexpression of CsGSTF1 and CsGSTU18 mediated reactive oxygen species (ROS) scavenging, whereas the virus-induced gene silencing (VIGS) of CsGSTF1 and CsGSTU18 caused strong CBC resistance and ROS burst. The present study investigated the characterization of citrus GST gene family, and discovered that CsGSTF1 and CsGSTU18 negatively contributed to CBC through modulating ROS homeostasis. These findings emphasize the significance of GSTs in infection resistance in plants. [ABSTRACT FROM AUTHOR]

Hesperidin is a dihydroflavonoids, accounting for more than 50% of the total flavonoids in Citri Reticulatae Pericarpium (CRP) of traditional Chinese medicine. It is an effective antioxidant and free radical scavenger that has anti-inflammatory, antiviral and hypoglycemic properties. The latest studies reported that hesperidin has a potential for novel coronavirus resistance. However, little is known about the synthesis regulation and accumulation site of hesperidin in plants. In this study, hesperidin synthase gene Crc1,6RhaT was cloned, and the protein can be completely transformed flavanone-7-O-glucoside into hesperidin in vitro and in vivo. Studies on biological characteristics of ovary walls and exocarps showed that the relative expression levels of the Crc1,6RhaT gene and protein decreased gradually with the development of citrus fruits, and the relative content of hesperidin firstly increased, then sequentially decreased. In situ hybridization results further revealed that Crc1,6RhaT transcription was mainly concentrated in the secretory cavity cells, which are revealed to be the site of flavonoid synthesis. Immunocytochemistry localization results showed that the Crc1,6RhaT was mainly located in the endoplasmic reticulum, nucleus and vacuole of secretory cells. We inferred that the Crc1,6RhaT was synthesized in the endoplasmic reticulum, then was transported into the vacuoles through enlarged vesicles at the end of the endoplasmic reticulum. Our results not only revealed that Crc1,6RhaT may be involved in the synthesis of hesperidin of the main bioactive substance in the medicinal plant Citrus reticulata 'Chachi' fruit, but also provided novel insights into the main subcellular sites of hesperidin biosynthesis in vacuoles. [ABSTRACT FROM AUTHOR]

Soil microbial necromass carbon (C) is a crucial component of the soil organic C pool. The impact of both straw mulching treatments and years on the soil microbial necromass C accumulation remains unclear. We investigated factors driving soil microbial necromass C accumulation and its role in improving yield by analyzing the dynamic response of microbial necromass C, total organic C (TOC) and available nutrients, genes encoding carbohydrate-degrading enzymes and fruit yield of citrus under different straw types of mulching (wheat, rice, oilseed rape, no mulch) from 2019 to 2022. Annual rainfall was the main factor affecting the soil bacterial necromass C (BNC) accumulation. Straw mulching treatments were the main factor affecting the soil fungal necromass C (FNC) accumulation. Increased annual rainfall and high soil moisture levels hindered the soil microbial necromass C accumulation, especially BNC. No correlation was found between BNC and the relative abundance of genes encoding peptidoglycan (bacteria-derived biomass) degrading enzymes. Decreased relative abundance of genes encoding chitin (fungal-derived biomass) degrading enzymes, particularly GH18, favored the accumulation of FNC. Actinomycetes were the most significant contributors of the GH18 gene among microbial phyla. Moreover, oilseed rape and rice mulching treatments reduced the relative abundance of genes encoding enzymes degrading chitin. Microbial necromass C, especially BNC, was key for sustaining TOC, supplying nutrients, and enhancing citrus fruit yield. Our results provide new information for optimizing straw mulch type and application time in citrus orchards to improve soil microbial necromass accumulation. [ABSTRACT FROM AUTHOR]

Citrus fruits are widely grown, processed, and distributed in more than 140 countries, with annual global production exceeding 124.3 million metric tons. This substantial consumption generates significant organic waste, accounting for approximately 50–60% of the total fruit mass, primarily in the form of peel, pulp, and seeds. Often discarded or reused as animal feed, these wastes contribute to significant environmental pollution and economic losses. Therefore, the valorization of these by-products represents an important opportunity to mitigate these challenges and improve the sustainability of the Citrus-related industry. This review highlights Citrus seed waste concerning its invaluable bioactive compounds, including fatty acids, phenolic compounds, limonoids, dietary fibers, vitamins, and carotenoids. Chemical compositions of Citrus seed biowaste differ depending on a variety of factors, such as Citrus variety, fruit maturity, environmental conditions, waste storage conditions, and extraction methods. The extraction and purification of phytochemicals from Citrus seed biowaste are one of the major procedures for valorizing waste. The two types of effective extraction methods are traditional (conventional extraction) and innovative (green extraction). Furthermore, Citrus seeds have been demonstrated to exhibit several biological activities and health-promoting properties including antioxidative, anti-inflammatory, and anti-cancer activities. Therefore, these wastes are safe and beneficial compounds used in the production of functional foods, nutraceuticals, pharmaceuticals, and cosmetics. A conclusion can be reached by emphasizing the abundance of bioactive compounds in Citrus seed wastes, which makes them an excellent opportunity for increased environmental and economic utilization. [ABSTRACT FROM AUTHOR]

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Drought stress poses increasingly serious threats to agricultural production in the era of global climate change. Arbuscular mycorrhizal (AM) fungi are well-recognized biostimulants promoting plant tolerance to drought stress. Lipids are indispensable for AM fungal colonization, however, the involvement of lipid metabolism in the drought tolerance conferred by AM fungi is largely unknown. In this study, we inoculated Poncirus trifoliata (L.) with Rhizophagus irregularis DAOM197198 under no drought stress, medium drought stress and severe drought stress, with non-inoculation under respective treatments as control. Results indicated that AM fungal inoculation significantly promoted the drought tolerance of P. trifoliata (L.), with the effect size decreasing along with drought severity. Moreover, the effect size was significantly related to arbuscule abundance. Fatty acid profiling showed that the arbuscule abundance was determined by the AM-specific phospholipids (PLs), whose biosynthesis and delivery were inhibited by drought stress as revealed by qRT-PCR of FatM, RAM1 and STR/STR2. More interestingly, AM fungal inoculation increased the lipid allocation to total PLs and the unsaturation rate of total neutral lipids (NLs), probably indicating the involvement of non-AM-specific lipids in the increased drought tolerance. Taken together, our results demonstrate that lipid metabolism in AM mediates the increased drought tolerance conferred by AM fungal inoculation, with AM-specific and non-AM-specific lipids functioning therein in different ways. [ABSTRACT FROM AUTHOR]

This study investigated the phenology and population dynamics of potential insect vectors of Xylella fastidiosa Wells et al. and other Auchenorrhyncha species in olive and citrus groves of Chania province, Crete, Greece. Although X. fastidiosa has not been reported in Greece, its introduction could cause serious diseases in many crops, including olives and citrus. Olive groves of Olea europaea L. 'Koroneiki' were sampled systematically using sweep net and Malaise traps over 24 months. One citrus grove was sampled for one year using a Malaise trap. Sweep net samples were taken from the herbaceous cover, tree canopy, and field borders of olive groves. Auchenorrhyncha were more abundant on the herbaceous cover compared to the canopy and field margins. Aphrophoridae species were mostly found on the herbaceous cover and in low numbers during fall (October–December) and spring (April–May). Cicadellidae species, such as Euscelis spp., were frequently found on the herbaceous cover of both olive and citrus groves. One Aphrophoridae and several Cicadellidae species were recorded in the citrus grove. Altitude was found to influence the population abundance of some Auchenorrhyncha species in olive groves. These results provide information for effective integrated management of insect vectors and their vector-borne pathogens. [ABSTRACT FROM AUTHOR]

Simple Summary: Citrus (Citrus spp.) is the world's largest fruit crop, both in terms of cultivation area and production. In recent years, the citrus industry in countries such as China, Brazil, and the United States has suffered significant damage due to the increasing severity of citrus diseases, such as Citrus Huanglongbing (HLB). Plant nucleotide-binding leucine-rich repeat (NLR) genes play a critical role in the plant immune system by helping plants resist pathogen infections. A thorough understanding of the diversity and evolution of citrus NLR genes is of great significance for the development of disease-resistant cultivars. In this study, we systematically identified 1585 NLR genes across 10 citrus genomes and conducted an in-depth analysis of their origins and evolutionary processes. NLR genes are crucial components of the effector-triggered immunity (ETI) system, responsible for recognizing pathogens and initiating immune responses. Although NLR genes in many plant species have been extensively studied, the diversity of NLR genes in citrus remains largely unknown. Our analysis revealed significant variations in the copy numbers of NLR genes among these species. Gene duplication and recombination were identified as the major driving forces behind this diversity. Additionally, horizontal gene transfer (HGT) emerged as the principal mechanism responsible for the increase in NLR gene copy number in A. buxifolia. The citrus NLR genes were classified into four categories: TIR-NBS-LRR (TNL), CC-NBS-LRR (CNL), RPW8-NBS-LRR (RNL), and NL. Our findings indicate that TNL, RNL, and CNL genes originated from NL genes through the acquisition of TIR and RPW8 domains, along with CC motifs, followed by the random loss of corresponding domains. Phylogenetic analysis suggested that citrus NLR genes originated alongside the species and underwent adaptive evolution, potentially playing crucial roles in the global colonization of citrus. This study provides important insights into the diversity of citrus NLR genes and serves as a foundational dataset for future research aimed at breeding disease-resistant citrus varieties. [ABSTRACT FROM AUTHOR]

Simple Summary: Tephritid fruit flies are major economic pests that impact fruit production and impede international trade. The type of host fruit influences the ability of a fruit fly to complete their life cycle. International regulatory standards that define host status categorize fruits as a natural host, a conditional host, or a nonhost. For those fruits that are natural or conditional hosts, the infestation rate can vary across a spectrum ranging from highly attractive well-suited hosts supporting large numbers of fruit flies to very poor hosts supporting low numbers. Persian lime, Citrus x latifolia, is a new crop in Hawai'i, and no information existed on its susceptibility to Hawai'i's tephritid fruit fly pests. Host status testing was conducted using no-choice laboratory and field cage tests as well as field collection of fruit. Mediterranean fruit fly and Oriental fruit fly oviposited and developed in artificially damaged (punctured) limes in cage tests but did not infest undamaged commercial quality fruit, suggesting Persian limes should be considered a conditional host. Field-collected and processed export-quality Persian limes (total of 45,954 fruit) were not naturally infested by Mediterranean fruit fly and Oriental fruit fly. In regulations, risk managers may use the term conditional nonhost to describe regulated articles, like Persian limes from Hawai'i, which do not pose a pest risk. We investigated the host status of harvest-ready green Persian lime, Citrus x latifolia Tan. (Rutaceae), to Oriental fruit fly (Bactrocera dorsalis [Hendel]) and Mediterranean fruit fly (Ceratitis capitata [Wiedemann]) (Diptera: Tephritidae) using laboratory and field studies. In forced-infestation small cage exposures (using 25 × 25 × 25 cm screened cages with 50 gravid females) and large olfactometer cage tests (using 2.9 × 2.9 × 2.5 m walk-in screened cages with 100 gravid females), punctured limes were infested by Oriental fruit fly and Mediterranean fruit fly at low rates compared to papaya controls, whereas undamaged intact fruit was not infested. Field collection and packing of 45,958 commercial export-grade fruit and subsequent incubation to look for natural infestation resulted in no emergence of fruit flies. Forced infestation studies in the field using sleeve cages to enclose fruit with a high density of fruit flies (50 gravid females) on the tree also showed no infestation. Commercial export-grade Persian lime fruit should be considered a conditional nonhost for Oriental fruit fly and Mediterranean fruit fly. [ABSTRACT FROM AUTHOR]

Extracellular enzymes produced by fungi can serve as a screening tool for entomopathogen candidates. Enzyme secretion ability is important in determining the virulence level of an entomopathogenic fungus. This study aims to see the potential of fungal isolates through chitinolytic, lipolytic, and proteolytic activities of five entomopathogenic fungal isolated from Bactrocera sp. imago from citrus plants. The research was carried out at the Microbiology Laboratory of the Department of Biology at the University of Lampung. Enzymatic activity is known through the method of observing the clear zone formed on agar media. Quantitative tests based on the calculation of enzymatic index values showed that Nigrospora sp. (IB1) had lipolytic activity, Penicillium sp. 2 (IB5) isolates had chitinolytic, lipolytic, and proteolytic activities. The isolates of Penicillium sp. 1 (IB2), Phytopthora sp. (IB3), and Gliocladium sp. (IB4) did not show the activity of the three enzymes. [ABSTRACT FROM AUTHOR]

Bujangseta is a technology used throughout the year to produce citrus fruits. This technology has economically succeeded in increasing the income of citrus farmers by 23.5%. Sustainable management of bujangseta technology is neede, one of which is maintaining the sustainability of the agroecosystem. A stable agroecosystem ensures the availability of ecosystem services through nutrient cycling and the natural control of pest and disease populations. The stability of agroecosystems is coherent with the high biodiversity of arthropods. This study aims to evaluate the effect of applying the citrus plant bujangseta in Karangwidoro village and Krajan village, Dau District, Malang Regency, East Java, from June to December 2022. The two application methods were light trapping (lighttrap) and pit trap (pitfall glass), and the results were analyzed using a t-test. The diversity index, species richness index, species evenness index, and dominance index were calculated. The results showed that the detrivores of the Collembola group dominated the diversity of arthropods, the primary pest of the Diaphorina citri, and the predatory arthropods of Paederus sp. and Braconidae. Diversity and community structure of arthopods indicated there at significant differences in diversity, dominance, evenness, and species richness in those two locations. Bujangseta in the Krajan has a higher community structure compared to the Karangwidoro, showing that the ecosystem at the Krajan location is better preserved. [ABSTRACT FROM AUTHOR]

The purpose of this study was to compare the efficacy of citrus peel phenolic compounds extracted using carboxylated multi -walled carbon nanotubes (MWCNT –COOH) with common synthetic antioxidants [butylhydroxyanisole (BHA) and butylhydroxytoluene (BHT)] in stabilizing sunflower oil (SO) during frying (180 ± 5 °C, 24 h). To evaluate the antioxidant activity of these compounds, total phenolic, and flavonoid contents, reducing power, ABTS scavenging activity, β -carotene bleaching ability, and 1, 1 -diphenyl - 2 - picrylhydrazyl (DPPH) radical scavenging activity were measured. Extracts were combined at various concentrations (100 -1000 ppm) with SO, and both synthetic antioxidants were standardized at 200 ppm. Thermal -oxidative stability was investigated by assessing the change in peroxide value (PV), color, free fatty acid (FFA) content, conjugated diene value (CDV), and thiobarbituric acid (TBA). Bitter orange peel extract (BPE) displayed a higher content of phenolic compounds and antioxidant activity. At 1000 ppm, it showed a lower FFA content, PV, TBA, and CDV. It can be used as an alternative to synthetic antioxidants. As a result, citrus peel phenolic compounds extracted with MWCNT –COOH can be used as preservatives in frying oils. [ABSTRACT FROM AUTHOR]

Citrus is one of the world's most important and widely produced fruit crops, with over a 100 million metric tons harvested from nearly 10 million hectares in 2023. Challenges in crop maintenance, production, and fruit quality necessitate developing new traits through Agrobacterium-mediated genetic transformation. While a few Agrobacterium strains (EHA105, GV3101, LBA4404) are known to transform citrus, many wild strains remain untested. We screened forty-one wild-type Agrobacterium strains isolated from various woody species and identified five capable of DNA transfer into citrus cells. Strain 1D1416 demonstrated the highest transient transformation frequency in Carrizo epicotyl explants (88%), outperforming the control EHA105 (84%) with comparable shoot regeneration rates (32% and 42%, respectively). Notably, 1D1416 exhibited no overgrowth and had the lowest necrosis and mortality rates in transformed tissues. It efficiently transferred the DsRed gene and induced galls in mature tissues of Mexican lime (70%), lemon (48%), Washington navel orange (25%), and clementine (6%). Genome sequencing of 1D1416 allowed for the disarming of the native T-DNA and addition of GAANTRY technology. This novel strain, combined with an optimized transformation procedure, make it a valuable tool for advancing citrus transformation. [ABSTRACT FROM AUTHOR]

'Redson' is a new triploid, red-fleshed pomelo x grapefruit hybrid. The goal of this study was to examine the effects of rainfall, harvest time, tree age, and yield on the postharvest storage performance of 'Redson' fruit. During 2022/23, two postharvest storage trials were conducted with early- and late-harvested fruit. The fruit from the early harvest retained good quality for up to 16 weeks of storage at 7.5 °C plus 1 week at 22 °C, whereas the late-harvested fruit suffered from a high decay incidence. During 2023/24, we expanded the postharvest trials to nine different fruit sets harvested from early season (late October) until the end of the season (January). Fruit quality was examined under the same storage conditions after 6 and 16 weeks, and the results indicated that early- and mid-season fruit retained good quality with minimal decay incidence even after prolonged storage for 16 weeks, whereas the late-season fruit suffered from significant decay incidences of 17–22% and a decline in flavor acceptability. Further analysis revealed strong and significant correlations between various rainfall parameters and harvest time and decay incidences. Overall, early-harvested fruit during the autumn had a superior postharvest storage performance, whereas late-harvested fruit during the rainy winter suffered from decay development. [ABSTRACT FROM AUTHOR]

For citrus trees cultivated by dwarf dense planting, the fruits are randomly distributed in space, which poses difficulties for mechanized picking. To improve picking efficiency, a citrus picking system based on dual robot collaboration is designed and a global scanning picking scheme that scans the entire fruit tree to achieve orderly fruit picking is proposed in this research. The dual‐robot calibration with the iterative method and closed‐form method is completed in the research. The picking problem is attributed to the single traveling salesman problem, and the trajectory planning and the picking task are completed with genetic algorithm in the research. The picking experiments are designed in the research. As a result, in the picking experiments, the average time for planning the picking sequence of citrus was 0.1184 s, the longest time is 0.1560 s. In each group of citrus picking experiments, the total picking time averaged 158.9 s, the longest group took 170 s, the picking success rate is 82%. The picking results show that the built dual‐machine system can effectively complete the picking task and meet the real‐time requirement of picking. The proposed dual‐robot picking system can provide a reference for the establishment of other picking robot system. [ABSTRACT FROM AUTHOR]

Blue mold disease, caused by Penicillium italicum (P. italicum), presents a significant challenge to orange fruits (Citrus sinensis L.) and other citrus crops globally. Biological control, particularly Trichoderma species, offers a promising alternative to synthetic fungicides. Therefore, this study aimed to isolate, identify, and evaluate the antagonistic activities of two Trichoderma isolates against P. italicum. These isolates were molecularly identified and assigned accession numbers PP002254 and PP002272, respectively. Both isolates demonstrated significant antifungal activity in dual culture assays. Moreover, the culture filtrates (CFs) of Trichoderma longibrachiatum PP002254 and Trichoderma harzianum PP002272 suppressed the mycelial growth of P. italicum by 77.22% and 71.66%, respectively. Additionally, CFs reduced the severity of blue mold on orange fruits by 26.85% and 53.81%, compared to 100% in the control group. Scanning electron microscopy revealed that treated P. italicum hyphae were shrunken and disfigured. Enzyme activities (catalase, peroxidase, polyphenol oxidase, and phenylalanine ammonia-lyase) in treated oranges increased, along with total soluble phenolics and flavonoids. Conversely, malondialdehyde (MDA) levels decreased in treated fruits. These findings suggest that T. longibrachiatum PP002254 and T. harzianum PP002272 could be effective biocontrol agents for managing blue mold and other citrus postharvest diseases. [ABSTRACT FROM AUTHOR]

The effect of N-(2-chloro-4-pyridyl)-N′-phenylurea (CPPU) on fruit splitting of 'Murcott' tangor fruit (Citrus reticulate × Citrus sinensis) was analyzed throughout two successive seasons during 2020 and 2021. 'Murcott' trees were treated with various concentrations of CPPU, 1.0, 5.0, and 10.0 mg·L−1, which significantly reduced the splitting of fruit compared with the control fruit and the gibberellic acid (GA3)-treated fruit (20.0 mg·L−1). The fruit treated with 5.0 mg·L−1 CPPU exhibited higher levels of fruit weight, longitudinal diameter, transverse diameter, peel strength, and peel thickness compared to the control fruit. In addition, the tree sprayed with 5.0 mg·L−1 CPPU had the greatest number of cellular layers and cells at the stylar end calculated in fruit. However, there were no other fruit quality characteristics significantly affected by CPPU and GA3 treatments. [ABSTRACT FROM AUTHOR]

Citrate is a major determinant of fruit flavor quality. Currently, citrus species and/or varieties with significant alterations in citrate level have greatly advanced the molecular basis of citrate accumulation in fruit. However, in-depth dissections of the molecular mechanism specific to citrate accumulation are still limited due to the lack of mutants, especially within one single variety. In this study, a fresh-sweet 'Shatangju' mutant (Citrus reticulata cv.) was obtained during a survey of citrus resources in Guangdong, China, and the phenotype, fruit morphology, and primary flavor profiles were comparatively analyzed. Unlike the wild-type 'Shatangju' (WT), the mutant (MT) material exhibited a dwarfed and multi-branched tree shape, delayed flowering and fruit ripening at maturity, a prolonged fruit tree-retention time, and a decreased single fruit weight at maturity. Dynamic measurement of the metabolite levels further suggested that the contents and fluctuation patterns of vitamin C, malate, quinate, and oxalate showed no obvious difference between MT and MT fruits, while the citrate level in MT fruits significantly decreased over various developmental stages, ranging from 0.356 to 1.91 mg g−1 FW. In addition, the accumulation patterns of the major soluble sugars (sucrose, fructose, and glucose), as well as the sugar/acid ratio, were also altered in MT fruits during development. Taken together, this study provides a novel acid-free 'Shatangju' mutant, which can serve as a powerful tool for the research of fruit flavor quality, especially for the comprehensive understanding of the molecular mechanism of citrate accumulation in fruits. [ABSTRACT FROM AUTHOR]

The Defective in Induced Resistance 1 (DIR1) gene, a member of the lipid transferase proteins (LTPs), plays a crucial role in plant defense against pathogens. While previous transcriptomic studies have highlighted the significant expression of citrus LTPs during biotic stress, functional annotations of LTPs in the Citrus genera remain limited. In this study, we cloned the Murraya paniculata DIR1 (MpDIR1(t)) gene and overexpressed it in Arabidopsis thaliana to evaluate its stress response mechanisms against biotic stress. The transgenic Arabidopsis lines showed fewer disease symptoms in response to Pseudomonas syringae (Pst DC3000) compared to wild-type Arabidopsis. Defense and pathogenesis-responsive genes such as PR1, PR4, PR5, and WRKY12 were significantly induced, showing a 2- to 12-fold increase in all transgenic lines compared to the wild type. In addition, the Pst DC3000-infected transgenic Arabidopsis lines demonstrated elevated levels of flavonoids and salicylic acid (SA), along with higher expression of SA-related genes, compared to the wild type. Moreover, all transgenic lines possessed lower reactive oxygen species levels and higher activity of antioxidant defense enzymes such as superoxide dismutase, peroxidase, and catalase under Pst DC3000 stress compared to the wild type. The up-regulation of defense genes, activation of the SA pathway, accumulation of flavonoids, and reinforcement of antioxidant defense mechanisms in transgenic Arabidopsis lines in response to Pst DC3000 underscore the critical role of MpDIR1(t) in fortifying plant immunity. Thus, MpDIR1(t) constitutes a promising candidate gene for improving bacterial disease resistance in commercial citrus cultivars. [ABSTRACT FROM AUTHOR]

Citrus fruits are among the most produced and traded agricultural products worldwide, with significant economic and social importance. Despite their importance in the European Union, Middle East, and Africa, the existing literature is limited. Several studies have reviewed different aspects of general agri-food supply chains, but a product-based literature review on citrus supply chains has not been conducted. This paper provides a comprehensive review of the citrus supply chain in these regions, identifying the key research topics, methodologies, and supply chain echelons addressed in the literature. The study employed a systematic review, real-world case studies, and supply chain stakeholders' interviews. This multi-faceted approach allows researchers to highlight research gaps, map a complete citrus supply chain, and provide a detailed material flow and sustainability-oriented overview of potential inputs and outputs at different stages. By incorporating real-world case studies and stakeholder interviews, this paper offers a nuanced and practical perspective on the operational and sustainability challenges unique to the citrus supply chain. This study serves as a guide for future research and enables practitioners to pinpoint areas and strategies for operational improvement across the supply chain. [ABSTRACT FROM AUTHOR]

The complexity of citrus phylogeny and taxonomy, influenced by polyembryony, genetic diversity, and extended generation cycles, necessitates assessing genetic relationships for improved production and disease resilience. DNA polymorphism markers are pivotal in genotyping and resolving phenotypic varietal ambiguities through accurate and objective genetic relatedness and distinctiveness assessments. In this study, 27 accessions of kagzi and ornamental lime were evaluated at morphological (based on IPGRI citrus descriptor), biochemical, and molecular levels using DNA-based markers, namely, random amplified polymorphic DNA (RAPD), start codon targeted (SCoT) polymorphism, and simple sequence repeats (SSR). Morphological analysis unveiled significant variation in leaf lamina attachment, shape, margins, fruit characteristics, and texture across all parameters. Biochemical research noted minimal differences, with total soluble solids (TSS) ranging from 5.7° to 8.0° Brix and titratable acidity (TA) from 0.36 to 0.50%. Notably, ornamental lime accessions exhibited higher TSS:TA ratios of 16.00. Molecular markers (RAPD, SCoT, and SSR) corroborated these findings, yielding 115, 74, and 64 amplicons, respectively, with polymorphic percentages varying from 33.33 to 100%. Polymorphic information content ranged from 0.20 to 0.90 for RAPD, 0.41 to 0.99 for SCoT, and 0.07 to 0.67 for SSR markers. Analysis of molecular variance (AMOVA) substantiated significant genetic differences among the kagzi and ornamental lime accessions (RAPD PhiPT = 0.267, SCoT PhiPT = 0.351, SSR PhiPT = 0.107). Furthermore, STRUCTURE software 2.3.4 revealed a ΔK value of two (K = 2), indicating two distinct genetic pools within the accessions, possibly attributable to bud mutations generating varying morphological traits within the same plant. Molecular marker-based germplasm characterization can mitigate confusion linked to morphological characteristics and multiple cultivar registrations. [ABSTRACT FROM AUTHOR]

This study evaluated the relationship between Zn in citrus leaves and some easily available soil properties using artificial neural network (ANN), gene expression programming (GEP), and stepwise regression methods. The data of 40 soil samples collected at the South of Kerman region (Iran) were used. Different combinations of input parameters, including soil texture, pH, organic carbon (OC), total neutralizing value (TNV), electrical conductivity (EC), and soil available P (Polsen), were considered. The coefficient of determination (R2), the normalized root means square error (NRMSE), mean absolute error (MAE), and Nash–Sutcliffe efficiency (NS) were used to evaluate the accuracy of the models. The results showed that the models with whole input parameters offered the lowest NRMSE and the highest R2. The ANN model with four input variables showed that 77% of the Zn variation in leaves could be elucidated by the explicit soil parameters, including clay, silt, OC, and Polsen. These results showed that the ANN model with six neurons in the hidden layer had the best performance in modeling Zn uptake. However, since the main goal of this research was to improve the models based on easily measurable variables, the GEP model with three input variables, including silt, OC, and Polsen, was found to be beneficial in estimating 71% of Zn-leaves variability. [ABSTRACT FROM AUTHOR]

Mastication trait of citrus significantly influences the fruit's overall quality and consumer preference. The accumulation of cellulose in fruits significantly impacts the mastication trait of citrus fruits, and the glycoside hydrolase 9 (GH9) family plays a crucial role in cellulose metabolism. In this study, we successfully identified 32 GH9 genes from the Citrus sinensis genome and subsequently conducted detailed bioinformatics analyses of the GH9 family. Additionally, we profiled the spatiotemporal expression patterns of CsGH9 genes across four distinct fruit tissue types and six crucial developmental stages of citrus fruits, leveraging transcriptome data. Parallel to this, we undertook a comparative analysis of transcriptome profiles and cellulose content among diverse fruit tissues spanning six developmental stages. Furthermore, to identify the pivotal genes involved in cellulose metabolism within the GH9 family during fruit maturity, we employed correlation analysis between cellulose content and gene expression in varying tissues across diverse citrus varieties. This analysis highlighted key genes such as CsGH9A2/6 and CsGH9B12/13/14/22. Collectively, this study provides an in-depth analysis of the GH9 gene family in citrus and offers novel molecular insights into the underlying mechanisms governing the mastication trait formation in citrus fruits. [ABSTRACT FROM AUTHOR]

CRISPR/Cas9-mediated gene editing requires high efficiency to be routinely implemented, especially in species which are laborious and slow to transform. This requirement intensifies further when targeting multiple genes simultaneously, which is required for genetic screening or more complex genome engineering. Species in the Citrus genus fall into this category. Here we describe a series of experiments with the collective aim of improving multiplex gene editing in the Carrizo citrange cultivar using tRNA-based sgRNA arrays. We evaluate a range of promoters for their efficacy in such experiments and achieve significant improvements by optimizing the expression of both the Cas9 endonuclease and the sgRNA array. In the case of the former we find the UBQ10 or RPS5a promoters from Arabidopsis driving the zCas9i endonuclease variant useful for achieving high levels of editing. The choice of promoter expressing the sgRNA array also had a large impact on gene editing efficiency across multiple targets. In this respect Pol III promoters perform especially well, but we also demonstrate that the UBQ10 and ES8Z promoters from Arabidopsis are robust alternatives. Ultimately, this study provides a quantitative insight into CRISPR/Cas9 vector design that has practical application in the simultaneous editing of multiple genes in Citrus, and potentially other eudicot plant species. [ABSTRACT FROM AUTHOR]

Introduction: Citrus hybrids with Poncirus trifoliata L. Raf. introgression have gained interest due to their tolerance to Huanglongbing (HLB), a devastating disease for Florida citrus agriculture. While these hybrids inherit disease tolerance from P. trifoliata, they sometimes also suffer from undesirable off-flavors. Methods: A selection of thirteen genotypes were harvested over the 2020-2021 and 2021-2022 seasons. Their juices were evaluated by a trained sensory panel and were comprehensively analyzed for their chemical makeup, including soluble solids content (SSC), titratable acidity (TA), volatiles, flavonoids and limonoids. Results & discussion: Overall, along with the commercial orange cultivars 'Valencia' and 'Hamlin', the HLB-tolerant Poncirus hybrid 'US SunDragon,' and the mandarin hybrids Sugar Belle¬, FF-5-51-2, and 'US Superna' had positive citrus flavor quality. Esters, some sesquiterpenes, along with flavonoids, eriocitrin and quercetin-3-(3R-glucosylrutinoside), were positively correlated with orange flavor while b-ionone and eucalyptol were highly abundant in the mandarins. The flavonoid linarin, was more abundant in Poncirus hybrids with off-flavors than in the Poncirus hybrid 'US SunDragon', having high orange flavor. Two mandarin hybrids, FF-5-6-36 and FTP-6-32-67, were not bitter at harvest, but the juice exhibited delayed bitterness after storage at -20°C, which was associated with significant increases of limonin, nomilin, naringenin, and prunin. Interestingly, during freezer storage, a newly identified flavonoid in citrus, tricin-C-hexoside, increased dramatically across all of the genotypes. The identification of diseasetolerant hybrids with satisfactory flavor quality at juicing as well as after storage where delayed bitterness may develop, has great significance for future breeding efforts for fresh fruit or for use in stand-alone juice/juice blends. [ABSTRACT FROM AUTHOR]

Citrus diseases caused by fungal pathogens drastically decreased the yield and quality of citrus fruits, leading to huge economic losses. Given the threats of chemical pesticides on the environment and human health, biocontrol agents have received considerable attention worldwide as ecofriendly and sustainable alternative to chemical fungicides. In the present study, we isolated a Bacillus velezensis strain TZ01 with potent antagonistic effect against three citrus pathogenic fungi: Diaporthe citri, Colletotrichum gloeosporioides and Alternaria alternata. The culture supernatant of this strain exhibited remarkable antifungal activity on potato dextrose agar plates and detached leaves of five citrus varieties. Treatment with TZ01 culture supernatant obviously affected the hyphal morphology and caused nucleic acid leakage. The crude lipopeptides (LPs) extracted from the culture supernatant were found as the major active ingredients, and could maintain the activity under a wide range of temperature and pH and ultraviolet radiation. Furthermore, the type of LPs, produced in vitro, were explored. Whole-genome sequencing of TZ01 revealed secondary metabolite gene clusters encoding synthetases for non-ribosomal peptides and polyketide production, and gene clusters responsible for the synthesis of three important LPs (surfactin, iturin, and fengycin) were identified in the genome. The liquid chromatography-mass spectrometry analysis confirmed the presence of various homologs of surfactin A, bacillomycin D, and fengycin A in the extracted LPs. Taken together, these results contribute to the possible biocontrol mechanisms of B. velezensis strain TZ01, as well as providing a promising new candidate strain as a biological control agent for controlling citrus fungal pathogens. [ABSTRACT FROM AUTHOR]

Lemon fruit (Citrus limon (L.) Burm.) is highly appreciated by consumers due to its antioxidant properties and health benefits. However, its shelf life can be limited by various factors, reducing the economy, and thereafter, new strategies to maintain the quality of lemons are necessary. Melatonin is a derivative of tryptamine, which is ubiquitously found in plants and has a wide range of functions regulating numerous physiological processes in plants. During two consecutive harvests, we evaluated the effect of preharvest treatments with melatonin on crop yield and on quality and functional properties of fruit of lemon cv. Verna at harvest and weekly after storage up to 28 days at 2 and 10 °C plus 2 days at 20 °C. Melatonin was applied as foliar spray treatments at dosages of 0.1, 0.3, and 0.5 mM and at three different stages of fruit development. The results showed that melatonin treatment had a positive impact on crop yield as well as in fruit quality parameters, such as firmness, content of bioactive compounds, and antioxidant activity, especially for a 0.5 mM dose. Taking all these effects into account, the application of melatonin along the growth cycle of fruit development could be considered a non-contaminant and eco-friendly tool for improving crop yield and quality of 'Verna' lemons at harvest and during postharvest storage. [ABSTRACT FROM AUTHOR]

Mandarin Chinese is typologically unusual among the world's languages in having flexible word order despite a near absence of inflectional morphology. These features of Mandarin challenge conventional linguistic notions such as subject and object and the divide between syntax and semantics. In the present study, we tested monolingual processing of argument structure in Mandarin verb-final sentences, where word order alone is not a reliable cue. We collected participants' responses to a forced agent-assignment task while measuring their electroencephalography data to capture real-time processing throughout each sentence. We found that sentence interpretation was not informed by word order in the absence of other cues, and while the coverbs BA and BEI were strong signals for agent selection, comprehension was a result of multiple cues. These results challenge previous reports of a linear ranking of cue strength. Event-related potentials showed that BA and BEI impacted participants' processing even before the verb was read and that role reversal anomalies elicited an N400 effect without a subsequent semantic P600. This study demonstrates that Mandarin sentence comprehension requires online interaction among cues in a language-specific manner, consistent with models that predict crosslinguistic differences in core sentence processing mechanisms. [ABSTRACT FROM AUTHOR]

Huanglongbing (HLB), associated with the psyllid-vectored phloem-limited bacterium, Candidatus Liberibacter asiaticus (CLas), is a disease threat to all citrus production worldwide. Currently, there are no sustainable curative or prophylactic treatments available. In this study, we utilized mass spectrometry (MS)-based metabolomics in combination with 3D molecular mapping to visualize complex chemistries within plant tissues to explore how these chemistries change in vivo in HLB-infected trees. We demonstrate how spatial information from molecular maps of branches and single leaves yields insight into the biology not accessible otherwise. In particular, we found evidence that flavonoid biosynthesis is disrupted in HLB-infected trees, and an increase in the polyamine, feruloylputrescine, is highly correlated with an increase in disease severity. Based on mechanistic details revealed by these molecular maps, followed by metabolic modeling, we formulated and tested the hypothesis that CLas infection either directly or indirectly converts the precursor compound, ferulic acid, to feruloylputrescine to suppress the antimicrobial effects of ferulic acid and biosynthetically downstream flavonoids. Using in vitro bioassays, we demonstrated that ferulic acid and bioflavonoids are indeed highly bactericidal to CLas, with the activity on par with a reference antibiotic, oxytetracycline, recently approved for HLB management. We propose these compounds should be evaluated as therapeutics alternatives to the antibiotics for HLB treatment. Overall, the utilized 3D metabolic mapping approach provides a promising methodological framework to identify pathogen-specific inhibitory compounds in planta for potential prophylactic or therapeutic applications. [ABSTRACT FROM AUTHOR]

Citrus fruit cultivation, especially mandarin oranges, is crucial to the economy of Nepal's hilly regions due to their ideal geoclimatic conditions. Despite its economic importance, the sector faces several challenges, such as inadequate grafting techniques, low-quality saplings, and ineffective post-harvest storage. This paper explores these issues and proposes innovative solutions through the use of Internet of Things (IoT) technology. To address these challenges, we identified key areas for improvement. First, we focused on extending grafting practices during the off-season to ensure a higher success rate and better-quality saplings. Second, we examined different post-harvest storage methods to determine their effectiveness in terms of shelf life, decay loss, and quality of fruit. In addition to exploring post-harvest strategies, this paper provides preharvest recommendations for farmers, emphasizing methods to enhance fruit quality and longevity through effective pre-storage practices. Our IoT-based approach introduces off-season grafting in polyhouses and advanced monitoring for post-harvest storage. The results are promising: We achieved grafting success rates of 91% for acid lime and 92% for local mandarin orange varieties. Additionally, our research compared different post-harvest storage methods for mandarin oranges, including room, cellar, and cold chamber. We assessed these methods based on shelf life, physiological weight loss, and the total soluble solids (TSS) to titratable acidity (TA) ratio. The cold chamber proved to be the most effective method, offering superior conditions for storing mandarin oranges. The IoT-based monitoring system played a crucial role in maintaining optimal temperature, humidity, and gas content within the cold chamber, resulting in reduced post-harvest losses and extended shelf life. These findings highlight the transformative potential of IoT technology in mandarin orange cultivation and post-harvest storage. [ABSTRACT FROM AUTHOR]

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]

Simple Summary: The main aim of this study was to identify antennally active pheromone components from the citrus long-horned beetle, Anoplophora chinensis, and to test them for behavioral activity. We identified three antennally active male-produced chemical components (nonanal, 4-(n-heptyloxy)butan-1-ol, and 4-(n-heptyloxy)butanal). When tested together in Y-tube behavioral assays, these three compounds were shown to be attractive to adult female A. chinensis. Pheromone production and behavior of A. chinensis are discussed in relation to other closely related Anoplophora cerambycid species. The citrus long-horned beetle, Anoplophora chinensis (Coleoptera: Cerambycidae), is a highly polyphagous species native to eastern and southeastern Asia. Detection of these beetles is dependent on visual surveys, which are inefficient and labor-intensive. The identification and development of pheromone-based lures would help improve survey efforts for A. chinensis should it become established within the US. We identified three antennally active male-produced chemical components (nonanal, 4-(n-heptyloxy)butan-1-ol, and 4-(n-heptyloxy)butanal), which were then tested for behavioral activity at our USDA Quarantine laboratory. When tested together in Y-tube behavioral assays, a three-component blend of the identified compounds was shown to be attractive to adult female A. chinensis. Pheromone production and behavior of A. chinensis and other closely related Anoplophora cerambycid species are discussed in relation to mate finding and potential monitoring. [ABSTRACT FROM AUTHOR]

Understanding canopy nitrogen (N) and phosphorus (P) differences is crucial for optimizing plant nutrient distribution and management. This study evaluated leaf N and P content in citrus trees across three cultivation modes: traditional mode (TM), wide-row and narrow-plant mode (WRNPM), and fenced mode (FM). We used hyperspectral data for non-destructive quantification and compared 1080 leaf samples from upper, middle, and lower canopy layers. Four models—Random Forest (RF), Backpropagation Neural Network (BPNN), Partial Least Squares (PLS), and Support Vector Machine (SVM)—were employed for leaf N and P estimation. Results showed that the TM had significantly lower N content compared to the WRNPM and FM, while the WRNPM exhibited higher P content. The canopy layer had minimal impact on N and P in the FM, and leaves in the upper layer had higher nutrient content in the WRNPM and TM. RF provided the best estimation accuracy, with R2 values of 0.66 for N and 0.72 for P. The cultivation mode and canopy layer significantly influenced the estimation accuracy, with the TM yielding the highest R2, followed by the WRNPM and FM obtaining the lowest accuracy. The labor-saving cultivation mode had different nutrient utilization efficiency compared to the TM. The cultivation mode and canopy layer should be considered when hyperspectral data were used for estimating the leaf N and P content. The study can offer new insights for precise fertilization strategies in fruit trees. [ABSTRACT FROM AUTHOR]

The "limón sutil" (Citrus aurantifolia) has been widely cultivated and well established for many years in Piura, northwestern Peru, because of its exceptional climate and soil conditions. However, decline and death of C. aurantifolia trees caused by different phytopathogens remain a common problem which has been observed in the last decades. It is known that the microbiota of soil plays an important role with their host and could be the starting point to understand the causes of citrus decline. In this study, we identified through culture-independent methods the bacterial and fungal microbiota associated to C. aurantifolia, C. jambhiri and C. volkameriana rhizospheres in the main areas of Piura. By using a 16S rRNA and ITS-metabarcoding analysis, we evaluated the taxonomic diversity between healthy trees and with decline symptoms and how this diversity could influence the health status of citrus trees. More than 600 and 200 bacterial and fungal ASVs were identified, respectively. Our metabarcoding analysis was able to identify Proteobacteria, Cyanobacteria, Firmicutes, Bacteroidota and Acidobacteriota prokaryotic phyla, while fungal phyla included Ascomycota, Basidiomycota and Glomeromycota. In addition, there were differences between microbial diversity indices in rhizospheres evaluated. Finally, bacterial and fungal genera were shared among the different citrus rhizospheres. These results have allowed us to obtain a preliminary identification of microbiota in the citrus rhizospheres of healthy trees and with decline symptoms. [ABSTRACT FROM AUTHOR]

The symptoms of huanglongbing (HLB), a disease caused by the bacterium Candidatus Liberibacter asiaticus (CLas), are visible on the canopy of citrus plants. They include mottling of leaves followed by dropping and lopsided fruits with premature dropping. Loss in phloem functionality and degradation of the root system are also HLB symptoms with a severe impact on plant growth and production. Some Citrus relatives, such as Poncirus trifoliata and its hybrids, have shown more tolerance to HLB disease and low titers of CLas compared to Citrus species, but little is known about the effects of CLas on their root system. In this study, we investigated the effects of CLas-infected 'Valencia' scion on the citrandarin IAC3222 (a hybrid between P. trifoliata and Sunki mandarin) used as rootstock as well as interstock between 'Valencia' and Swingle citrumelo rootstock. At 13 months post-inoculation, the cycle threshold values (CT) for CLas in the infected scion samples indicated a high CLas titer (from 15.9 to 22.7) regardless of the rootstock variety or interstock used. However, no CLas-positive samples were detected in the roots of IAC3222 (CT ranging from 37.9 to 40.0), in contrast to all Swingle roots (CT ranging from 27.9 to 31.3). Both root volume and mass were reduced in IAC3222 compared to uninfected 'Valencia' scion, suggesting that scion infection damages roots, regardless of whether they are contaminated or not by CLas. The damage to the root system of IAC3222 was significantly less severe than that of the Swingle rootstock. Multivariate hierarchical analysis considering all evaluated parameters clustered the CLas-infected plants grafted on IAC3222 together with the non-inoculated plants. We concluded that the IAC3222 rootstock was less affected by the CLas-infected scion compared to the Swingle rootstock and is a promising rootstock to minimize the HLB effect on plant development. [ABSTRACT FROM AUTHOR]

Transposable elements (TEs) significantly contribute to the evolution and diversity of plant genomes. In this study, we explored the roles of TEs in the genomes of Citrus and Citrus-related genera by constructing a pan-genome TE library from 20 published genomes of Citrus and Citrus-related accessions. Our results revealed an increase in TE content and the number of TE types compared to the original annotations, as well as a decrease in the content of unclassified TEs. The average length of TEs per assembly was approximately 194.23 Mb, representing 41.76% (Murraya paniculata) to 64.76% (Citrus gilletiana) of the genomes, with a mean value of 56.95%. A significant positive correlation was found between genome size and both the number of TE types and TE content. Consistent with the difference in mean whole-genome size (39.83 Mb) between Citrus and Citrus-related genera, Citrus genomes contained an average of 34.36 Mb more TE sequences than Citrus-related genomes. Analysis of the estimated insertion time and half-life of long terminal repeat retrotransposons (LTR-RTs) suggested that TE removal was not the primary factor contributing to the differences among genomes. These findings collectively indicate that TEs are the primary determinants of genome size and play a major role in shaping genome structures. Principal coordinate analysis (PCoA) of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) identifiers revealed that the fragmented TEs were predominantly derived from ancestral genomes, while intact TEs were crucial in the recent evolutionary diversification of Citrus. Moreover, the presence or absence of intact TEs near the AdhE superfamily was closely associated with the bitterness trait in the Citrus species. Overall, this study enhances TE annotation in Citrus and Citrus-related genomes and provides valuable data for future genetic breeding and agronomic trait research in Citrus. [ABSTRACT FROM AUTHOR]

The prolonged utilization of copper (Cu)-containing fungicides results in Cu accumulation and affects soil ecological health. Thus, a pot experiment was conducted using Citrus reticulata cv. Shatangju with five Cu levels (38, 108, 178, 318, and 388 mg kg−1) to evaluate the impacts of the soil microbial processes, chemistry properties, and citrus growth. These results revealed that, with the soil Cu levels increased, the soil total Cu (TCu), available Cu (ACu), organic matter (SOM), available potassium (AK), and pH increased while the soil available phosphorus (AP) and alkali-hydrolyzable nitrogen (AN) decreased. Moreover, the soil extracellular enzyme activities related to C and P metabolism decreased while the enzymes related to N metabolism increased, and the expression of soil genes involved in C, N, and P cycling was regulated. Moreover, it was observed that tolerant microorganisms (e.g., p_Proteobacteria, p_Actinobacteria, g_Lysobacter, g_Sphingobium, f_Aspergillaceae, and g_Penicillium) were enriched but sensitive taxa (p_Myxococcota) were suppressed in the citrus rhizosphere. The citrus biomass was mainly positively correlated with soil AN and AP; plant N and P were mainly positively correlated with soil AP, AN, and acid phosphatase (ACP); and plant K was mainly negatively related with soil β−glucosidase (βG) and positively related with the soil fungal Shannon index. The dominant bacterial taxa p_Actinobacteriota presented positively correlated with the plant biomass and plant N, P, and K and was negatively correlated with plant Cu. The dominant fungal taxa p_Ascomycota was positively related to plant Cu but negatively with the plant biomass and plant N, P, and K. Notably, arbuscular mycorrhizal fungi (p_Glomeromycota) were positively related with plant P below soil Cu 108 mg kg−1, and pathogenic fungi (p_Mortierellomycota) was negatively correlated with plant K above soil Cu 178 mg kg−1. These findings provided a new perspective on soil microbes and chemistry properties and the healthy development of the citrus industry at increasing soil Cu levels. [ABSTRACT FROM AUTHOR]

Citrus species are widely cultivated across the globe and frequently encounter drought stress during their growth and development phases. Previous research has indicated that citrus species synthesize flavonoids as a response mechanism to drought stress. This study aimed to comprehensively quantify and analyze the presence of 85 distinct flavonoids in the leaf and root tissues of lemon (drought susceptible) and sour orange (drought tolerant). In drought-stressed sour orange roots, flavonoids, such as isosakuranin, mangiferin, trilobatin, liquiritigenin, avicularin, silibinin, and glabridin, were more elevated than control sour orange roots and drought-stressed lemon roots. Additionally, hydroxysafflor yellow A, cynaroside, tiliroside, and apigenin 7-glucoside were increased in drought-stressed sour orange leaves compared to drought-stressed lemon leaves. Under drought stress, flavonoids such as (-)-epigallocatechin, silibinin, benzylideneacetophenone, trilobatin, isorhamnetin, 3,7,4′-trihydroxyflavone, and liquiritigenin were significantly increased, by 3.01-, 3.01-, 2.59-, 2.43-, 2.07-, 2.05-, and 2.01-fold, in sour orange roots compared to control sour orange roots. Moreover, the total flavonoid content and antioxidant capacity were significantly increased in drought-stressed sour orange leaves and root tissues compared to drought-stressed lemon leaves and root tissues. The expression levels of genes involved in flavonoid biosynthesis were highly expressed in sour orange leaves and roots, compared to lemon leaves and root tissues, post-drought stress. These findings indicate that lemons fail to synthesize protective flavonoids under drought conditions, whereas sour orange leaves and root tissues enhance flavonoid synthesis, with higher antioxidant activities to mitigate the adverse effects of reactive oxygen species generated during drought stress. [ABSTRACT FROM AUTHOR]