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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.

BACKGROUND: Late‐ripening citrus plays an important role in the stability of the global citrus industry. However, the regreening phenomenon in Valencia oranges impacts the peel color and commercial value. Ethylene degreening is an effective technique to improve the color of citrus fruits, but this effect may be delayed in regreened oranges. To better clarify this phenomenon, plastid morphology, pigment and phytohormone content in ethephon‐degreened Midknight Valencia oranges harvested in different stages were evaluated. RESULTS: Results showed that in fruits harvested at the turning stage, ethephon degreening treatment induced a chloroplast‐to‐chromoplast transition, and chlorophyll degradation and carotenoid accumulation were accelerated. Conversely, in fruits harvested at the regreening stage, the changes in plastid morphology were minimal, with delayed changes in chlorophyll and carotenoids. Genes related to ethylene biosynthesis and signaling pathways supported these responses. Variations in endogenous auxin, jasmonic acid, abscisic acid and gibberellins could partially explain this phenomenon. CONCLUSION: The response of Midknight Valencia oranges to ethephon degreening was delayed in the regreening stage, possibly due to the dynamic variations in endogenous phytohormones. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

The editorial in "Frontiers in Plant Science" explores the molecular interactions between plants and insects, focusing on defense mechanisms and resistance genes. The research delves into the complex genetic and metabolic processes involved in plant-insect interactions, using advanced omics technologies. Specific studies highlighted in the editorial include the interaction between rice and the brown planthopper, as well as aphid-mediated tritrophic interactions and psyllid-pathogen interactions. The articles provide valuable insights into the molecular arms race between plants and insects, aiming to enhance pest control strategies and sustainable crop production. [Extracted from the article]

The editorial discusses the significant role of microorganisms and their metabolites in agriculture, food production, and environmental sustainability. Microbes like plant growth-promoting rhizobacteria and arbuscular mycorrhizal fungi enhance soil fertility and crop resilience, while microbial metabolites offer eco-friendly biocontrol solutions. Research highlights the potential of engineered microbial communities for sustainable agriculture, food safety, and environmental restoration, emphasizing the need for further exploration in optimizing microbial interactions and biodegradation pathways. The studies presented in the editorial showcase advancements in leveraging microorganisms for various applications, underscoring the importance of microbial solutions in achieving global food security and environmental health. [Extracted from the article]

Fast and effective monitoring and surveillance techniques are crucial for the swift implementation of control methods to prevent the spread of Huanglongbing, a devastating citrus disease, and its invasive psyllid vector, Asian citrus psyllid, Diaphorina citri, into South Africa, as well as to control the native vector, African citrus triozid, Trioza erytreae. Monitoring for citrus psyllid pests can be improved by using semiochemical odorants to augment already visually attractive yellow sticky traps. However, environmental variables such as temperature and humidity could influence odorant release rates. Five field cages were used to test the ability of a selection of odorants to improve yellow sticky trap efficacy in capturing citrus psyllids. Environmental effects on odorant loss from the dispensers were also investigated. The odorants that most improved yellow sticky trap captures in field cages were then tested under open field conditions alongside lower concentrations of those same lures. Gas chromatography-mass spectrometry was used to calculate odorant release rates as well as to determine if any contamination occurred under field conditions. None of the odorants under field cage or field conditions significantly improved psyllid capture on yellow sticky traps. Temperature influenced odorant loss, and release rate from polyethylene bulbs decreased over time. Based on these results, the use of unbaited yellow sticky traps seems to be the most effective method for monitoring of Huanglongbing vectors. [ABSTRACT FROM AUTHOR]

Since its inception, antisense oligonucleotides (ASOs) have been extensively used in functional genomics. Recent advancements in chemical modification and delivery technology extend its applications to the targeted management of crop pests. ASO was conceptualized in the early 1970s and first applied to inhibit retrovirus replication in chickens. The principles of ASOs rely on target complementarity by hybridizing with the mRNA and inhibiting the function. However, the application of ASO received little attention because of its high instability in the biological environment. Initial ASOs, featuring phosphorothioate linkages, laid the groundwork for subsequent advancements, by addressing challenges such as nuclease degradation and cellular uptake limitations. The second generation introduced 2'-modifications to enhance stability and specificity while allowing reversible gene regulation. Third-generation ASOs incorporated innovative chemical modifications like locked nucleic acids (LNAs), peptide nucleic acids (PNAs), phosphoramidate morpholino oligomers (PMOs), 2′-deoxy-2′-fluoro-d-arabinonucleic acid (FANA), cyclohexene nucleic acids (CeNAs), and tricyclo-DNA (tcDNA), offering enhanced efficacy and stability. ASO technology continues to evolve, promising precision medicine and customized therapies for genetic diseases. In agriculture, ASOs selectively target essential genes in pests or pathogens, which would be a novel option for providing precise crop protection and reducing reliance on conventional pesticides. Recent studies demonstrated successful ASO application in thrips, psyllids, Gypsy moths, scale insects, citrus greening, and Zebra-chip diseases. Additionally, ASOs hold the potential for improving crop yield and quality by modulating gene expression related to plant growth, development, and stress responses. They can enhance abiotic stress tolerance, regulate genes associated with specific traits, and offer alternative strategies for managing diseases, such as targeting S-genes in tomatoes for resistance against bacterial spots. These applications antecede the oligo-based pesticides that will revolutionize future agriculture by reducing pesticide uses and harmful impacts on the ecosystem. Further advancements in environmental stability, field efficacy, delivery formulation, and environmental safety would mold this technology into a novel tool for sustainable crop protection. This review highlights the fundamentals of ASO, recent advancements in design chemistry, delivery systems, validation and optimization process, and its potential in customized pest management. This would serve as a ready reckoner for future ASO research and application. [ABSTRACT FROM AUTHOR]

Citrus tristeza virus (CTV) is a causal agent of diseases that have challenged the global citrus production for more than a century. The disease named 'tristeza', which means 'sadness' in Portuguese and Spanish, has spread by aphids and vegetative propagation, resulting in costly pandemics that reshaped the world citrus production by forcing the adaption of disease‐tolerant rootstocks. Furthermore, management of the second major CTV‐induced disease, stem pitting, became a unique example of the use of cross‐protection on a large nationwide scale, allowing many citrus growing regions to control the disease that could not be managed through horticultural practices. The information gathered in this review commemorates a hundred years of research on the virus and the respective diseases, which began with classical horticultural approaches and advanced toward the cutting‐edge molecular biology studies. In this regard, it is proper to mention that CTV research greatly benefited from close international collaboration between research institutions and scientists from the affected and nonaffected citrus areas. Moreover, despite the considerable initial losses caused by tristeza, the world's fresh fruit and juice concentrate citrus industries reemerged as highly productive following the research advancements, a situation that changed throughout Florida and Brazil in the past two decades or so with the outbreak of the devastating citrus greening (Huanglongbing) bacterial disease. This review encompasses past and recent advances in the CTV research positioning the citrus‐CTV pathosystem as a pivotal model system for investigating virus interactions with perennial woody hosts. The review will also serve as an updated version of the respective section on CTV in the Description of Plant Viruses that the Association of Applied Biologists manages. We dedicated this review to the 85th Birthday celebration of Prof. Moshe Bar‐Joseph, a world‐renowned plant pathologist whose half‐a‐century‐long career devoted to citrus diseases yielded many important, pioneering discoveries on CTV and other closteroviruses. Many of those are highlighted in this review. Prof. Bar‐Joseph retired from the Volcani Center, Agricultural Research Organization in Israel several years ago, yet he continues to be actively engaged in research and provides his expertise to citrus pathologists around the world in the present days. [ABSTRACT FROM AUTHOR]

Penicillium digitatum Sacc is a common postharvest pathogen affecting lime fruits. It causes significant losses in postharvest lime production. An emerging alternative to chemical control is the use of environmentally friendly such as edible and biodegradable films and packaging. The goal of the current study was to test different concentrations of Aloe vera gel (5, 15, 25, 50, 75, and 100% v/v), tea tree oil coating (0.5, 1, 2.5, 5, and 10% v/v), and their combination for controlling P. digitatum in vitro. The results revealed that specific concentrations of Aloe vera gel (75% and 100% v/v), tea tree oil (2.5, 5, and 10% v/v), and Aloe vera gel (25%) + tea tree oil (1%) v/v showed the highest inhibitory effect against the pathogen. The most effective concentrations of Aloe vera gel (75%), tea tree oil (2.5%), and Aloe vera gel (25%) + tea tree oil (1%) were evaluated against the green mold disease of lime under natural infection through storage period (0, 7, 14, 21, and 28 days). Compared to the control group, all edible layers demonstrated a significant delay and reduced in disease severity percentage throughout the storage periods. However, coating lime fruits with a combination of Aloe vera gel (25%) + tea tree oil (1%) successfully prevented the green mold disease of lime fruits over 28 days. The impact of these coatings was evaluated on lime fruit quality maintenance (weight loss, firmness, juice weight, total soluble solids, total acidity, pH, vitamin C, lipid peroxidation content, total phenols, total flavonoid, and total protein) over 28 days of storage during the 2021 and 2022 seasons. All treatments improved fruit quality through the storage period compared with untreated fruits. Treated lime fruits with Aloe vera gel (25%) + tea tree oil (1%) exhibited slight reductions in weight loss and juice weight compared to alternative treatments as an average of the two successive seasons. Simultaneously, this treatment improved fruit firmness, vitamin C levels, total phenols, total flavonoid, and total protein when contrasted with other treatments as an average of the two studied seasons. These findings show that the combination of Aloe vera gel and tea tree oil coatings enhances the shelf life and maintains the quality of lime fruits. They can also be used as an environmentally acceptable, chemical-free alternative treatment to preserve the postharvest quality of lime fruit. [ABSTRACT FROM AUTHOR]

Citrus huanglongbing (HLB) is a major challenge that impacts the flourishing of the citrus industry. Therefore, analyzing the genomic information of HLB-resistant or tolerant citrus resources is crucial for breeding HLB-resistant citrus varieties. The Carrizo citrange, a hybrid of Citrus sinensis and Poncirus trifoliata, plays a pivotal role in citrus cultivation. However, its genetic explorations are difficult due to the absence of a reference genome or full-length transcriptome. In order to enhance our understanding of the genetic information of citrange, we conducted a full-length transcriptomic sequencing of multiple tissues from the Carrizo citrange using the PacBio Sequel II platform. Moreover, we performed gene ontology (GO) annotation, gene functional annotation, simple sequence repeats (SSR) types analysis, as well as identification of lncRNAs, alternative splicing events, and analysis of pathogen defense-related genes. Results showed that a total of 43,452 isoforms were generated, with 43,307 of them being annotated. GO annotation indicated the involvement of these isoforms in various biological processes, cellular components, and molecular functions. The coding sequence length of the isoforms ranged from 1,000 to 4,000 base pairs (bp). Moreover, we have discovered 54 varieties of transcription factors and regulators, along with 16 classifications of genes associated with resistance. Among all types of SSRs, trimer type SSRs were the most abundant. 130 lncRNAs were predicted to be highly reliable in the isoforms of the Carrizo citrange, with alternative splicing events identified, and the most frequent being retained intron. The analysis of gene family expansion and contraction revealed a significant increase in pathogen defense-related genes within the Carrizo citrange. The results of this study will be of great value for future investigations into gene function in citrange and for expanding the genetic pool for breeding citrus varieties resistant or tolerant to HLB. [ABSTRACT FROM AUTHOR]

The editorial in "Frontiers in Plant Science" discusses the molecular interactions between plants and insects, focusing on defense mechanisms and strategies used by both organisms. The research topic explores the genetic, metabolic, and molecular interactions between herbivorous insects and host plants, using advanced omics technologies. Specific articles in the research topic delve into the interaction between rice and the brown planthopper, highlighting the molecular mechanisms of resistance genes such as Bph6, Bph14, Bph15, and Bph30. Additionally, the editorial covers studies on aphids as vectors in tritrophic interactions and psyllids as vectors in vector-pathogen interactions. [Extracted from the article]

BACKGROUND: Asian citrus psyllid, Diaphorina citri, is a hemipteran that vectors the causal pathogen of citrus greening disease, or huanglongbing (HLB). HLB is a tree killing disease that has severely limited citrus production globally. Unfortunately, there is no cure for this disease, and mitigation depends on multiple insecticide applications to reduce vector populations. Silencing of cytochrome P450 expression associated with detoxification enzymes by RNA interference is known to increase susceptibility of D. citri to insecticides. However, dsRNA was previously introduced into psyllids by topical applications. The possible application of this technology for pest management will require effective field delivery of the dsRNA. Therefore, we evaluated a virus vector (Citrus tristeza virus; 'mild strain' T36) to deliver gene silencing directly to this sap‐sucking insect via plant phloem. Citrus macrophylla plants inoculated with CTV expressing a truncated consensus sequence of CYP450 (CTV‐tCYP450) constantly produced small interfering RNA in the plant phloem that targeted five cytochrome p540 (CYP450) genes in D. citri. RESULTS: Insecticide susceptible D. citri reared on citrus infected with CTV‐tCYP450 were subsequently more susceptible to imidacloprid, fenpropathrin, carbaryl, and chlorpyrifos than those reared on citrus infected with wildtype CTV or non‐infected negative controls. Additionally, nymph survival and adult lifespan were significantly reduced when psyllids were reared on CTV‐tCYP450 citrus plants compared with controls. Interestingly, similar results were obtained after one and two generations of rearing. Finally, field‐collected psyllids from areas with known broad‐spectrum insecticide resistance were rendered more susceptible to imidacloprid and fenpropathrin after feeding on CTV‐tCYP450 citrus trees as compared with those reared on controls. CONCLUSION: The integration of citrus‐mediated RNA inference targeting psyllid detoxification enzymes could function as a resistance management tool and reduce insecticide input in an integrated pest management program for HLB. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Citrus huanglongbing (HLB), which is caused by the phloem-colonizing bacteria Candidatus Liberibacter asiaticus (CLas), poses a significant threat to citrus production worldwide. The pathogenicity mechanism of HLB remains poorly understood. SEC-dependent effectors (SDEs) have been suggested to play critical roles in the interaction between citrus and CLas. Here, we explored the function of CLIBASIA_05320 (SDE19), a core SDE from CLas, and its interaction with its host target. Our data revealed that SDE19 is expressed at higher level during infection of citrus than that during infection of the Asian citrus psyllid. Subcellular localization assays showed that SDE19 is localized in the nucleus and cytoplasm and is capable of moving from cell to cell in Nicotiana benthamiana. To investigate whether SDE19 facilitates pathogen infection, we generated transgenic Arabidopsis thaliana and citrus plants overexpressing SDE19. Transgenic A. thaliana and citrus plants were more susceptible to Pseudomonas syringae pv. tomato (Pst) and Xanthomonas citri subsp. citri (Xcc), respectively. In addition, RNA-seq analysis demonstrated that overexpression of SDE19 resulted in a reprogramming of expression of genes related to biotic stimulus responses. SDE19 interacts with Citrus sinensis Sec12, a guanine nucleotide exchange factor responsible for the assembly of plant COPII (coat protein II)-coated vesicles, which mediate vesicle trafficking from the ER to the Golgi. SDE19 colocalizes with Sec12 in the ER by binding to its N-terminal catalytic region, affecting the stability of Sec12 through the 26S proteasome. This interaction hinders the secretion of apoplastic defense-related proteins such as PR1, P69B, GmGIP1, and RCR3. Furthermore, the secretion of PR1 and callose deposition is decreased in SDE19-transgenic A. thaliana. Taken together, SDE19 is a novel virulent SDE secreted by CLas that interacts with Sec12 to disrupt vesicle trafficking, inhibit defense-related proteins secretion, and promote bacterial infection. This study sheds light on how CLas manipulates the host vesicle trafficking pathway to suppress the secretion of defense-related proteins and interfere with plant immunity. Author summary: SEC-dependent effectors play a crucial role in the infection process of Candidatus Liberibacter asiaticus (CLas) in plants. However, the specific functions of most SDEs remain poorly understood. Here, we conducted functional analyses of SDE19, a core SDE, and revealed that it suppresses plant immunity and interferes with vesicle trafficking. We found that SDE19 is able to move intercellularly within plants and suppress the expression of defense-related genes and callose deposition to suppress plant immunity. Furthermore, overexpression of SDE19 enhances susceptibility of transgenic plants to bacterial infection. Specifically, SDE19 targets and destabilizes a citrus guanine nucleotide exchange factor, to interfere with host vesicle trafficking and inhibit the secretion of defense-related proteins. Our study revealed a new mechanism by which CLas suppresses plant immunity via interfering with vesicle trafficking. [ABSTRACT FROM AUTHOR]

The tomato-potato psyllid, Bactericera cockerelli (Šulc), belonging to the Hemiptera order, is an insect pest of solanaceous crops and vectors a fastidious bacterium, Candidatus Liberibacter solanacearum (CLso), the presumptive causal agent of zebra chip and vein greening diseases in potatoes and tomatoes, respectively. The genome of B. cockerelli has been sequenced recently, providing new avenues to elucidate mechanistic insights into pathogenesis in vegetable crops. In this study, we performed RNA-sequencing of the critical psyllid organs (salivary glands and ovaries) involved in CLso pathology and transmission to host plants. Transcriptome analysis revealed differentially expressed genes and organ-specific enrichment of gene ontology (GO) terms related to metabolic processes, response to stress/stimulus, phagocytosis, proteolysis, endocytosis, and provided candidate genes encoding transcription factors (TFs). To examine gene regulatory networks across the psyllid organs under CLso(-) and CLso(+) conditions, we performed weighted gene co-expression network analysis (WGCNA), and unique modules differentiating the psyllid organs were identified. A comparative GO analysis of the unique gene modules revealed functional terms enriched in response to stress, gene regulation, and cell division processes in the ovaries. In contrast, respiration, transport, and neuronal transmission-related GO terms were enriched in the salivary glands. Altogether, this study reveals new insights into tissue-specific expression of the psyllid organs in the absence or presence of CLso bacterium. This knowledge can be leveraged to develop new pest and disease management strategies by delineating the regulatory networks involved in the psyllid-CLso interaction. [ABSTRACT FROM AUTHOR]

Imidacloprid (IDP) is an active ingredient of the Admire brand pesticide used to control the vector (Asian citrus psyllid) that transmits the causative organism Candidatus Liberibacter asiaticus (CLas) for citrus greening or huanglongbing disease. Imidacloprid products are applied via soil drench where citrus roots are mostly concentrated which is between 0 and 60 cm depth. These soil depths exhibit different characteristics that may affect IDP leaching beyond the rooting zone. Representative soil samples were collected from Entisols and Ultisols, which are the dominant soil orders under citrus production in central Florida, at 15 cm increments up to 60 cm to estimate and understand the batch sorption, kinetics, equilibria, and degradation of IDP. Results showed that the equilibrium time for IDP at 0–15 cm depth (10 hours) was 2 times faster than at 15–60 cm (20 hours) for the Entisol. Nevertheless, all depths reached equilibrium within 24 hours for the Entisol. The 0–30 cm depth adsorbed 2 times more IDP than the 30–60 cm depth for both soils. Nevertheless, the adsorption coefficient was approximately ≤ 1 mL g-1 for both soils. The half-life of IDP in both soils ranged from 10 to 17 days. The Entisol showed higher adsorption than the Ultisol at both depths, probably due to relatively lower organic carbon (OC) content in the Ultisol compared to the Entisol. Thus, the Ultisol showed high IDP leaching vulnerability compared to the Entisol. Movement of IDP is affected by the amount of OC in the citrus critical zone. [ABSTRACT FROM AUTHOR]

Several Persian lime trees were found to exhibit dieback and yellowing during monitoring of the intensity of Huanglongbing disease on a 6-year-old commercial Persian lime orchard in San Rafael, Veracruz, Mexico, between August and October 2022. During the examination of the trees, we discovered small holes on the bark of the main stem and lower branches, significant cracking of the bark, and beetles crawling on the surface. Removal of the bark on the crevices showed the presence of larvae and adults plausibly feeding from the inner bark tissue. Phloeonemus interruptus (Coleoptera: Zopheridae) adults were found. Although it is unknown whether P. interruptus will become invasive, this study confirmed that it is associated with Persian lime trees. Thus, this serves as a bellwether to warn of the potential direct damage or transmission of fungi or oomycetes, such as those in the genera Lasiodiplodia and Phytophthora. To the best of our knowledge, this is the first report of the association of Phloeonemus interruptus with Persian lime (Citrus latifolia Tan. Rutaceae) in the central region of Veracruz, Mexico. [ABSTRACT FROM AUTHOR]

Agriculture plays an essential role in Thailand economy. However, to control plant pathogens and maximize crop yield, pesticides are overused and misused. This results in toxic pollutants that are harmful to humans and the environment. Biological control offers an alternative to the use of synthetic chemicals. Mandarin orange (Citrus reticulata) is widely grown and consumed in Thailand, but it is threatened by green mould disease caused by Penicillium digitatum, which usually occurs at post-harvest storage. A total of 40 isolates of epiphytic yeasts were isolated from symptomless orange peels. They were screened for antagonistic activity against P. digitatum originally isolated from a diseased orange using a dual culture method. Five isolates exhibited at least 70% inhibition; therefore, they were further screened for their activity on orange using fruit inoculation. An isolate, AL3, reduced the disease incidence (79%) and lesion size (34.75±2.57 mm) caused by P. digitatum compared to the control treatments (disease incidence, 100% and lesion size, 50.00±1.03 mm, respectively). The yeast was analyzed using molecular data based on Internal Transcribed Spacers (ITS region) and it was identified as Pichia bruneiensis AL3. Its mode of action on anti-sporulation was studied. When tested on agar plates, living cells and culture broth of P. bruneiensis AL3 were able to inhibit spore germination of P. digitatum resulting in 33.2 and 38.2% germination, respectively, compared to the control treatment (76.8% germination). These results showed that P. bruneiensis AL3 has the potential to develop as a biological control agent (BCA). [ABSTRACT FROM AUTHOR]

Cassava is an important food crop in western Kenya, yet its production is challenged by pests and diseases that require routine monitoring to guide development and deployment of control strategies. Field surveys were conducted in 2022 and 2023 to determine the prevalence, incidence and severity of cassava mosaic disease (CMD) and cassava brown streak disease (CBSD), whitefly numbers and incidence of cassava green mite (CGM) in six counties of western Kenya. Details of the encountered cassava varieties were carefully recorded to determine the adoption of improved varieties. A total of 29 varieties were recorded, out of which 13 were improved, although the improved varieties were predominant in 60% of fields and the most widely grown variety was MM96/4271. The CMD incidence was higher in 2022 (26.4%) compared to 2023 (10.1%), although the proportion of CMD attributable to whitefly infection was greater (50.6%) in 2023 than in 2022 (18.0%). The CBSD incidence in 2022 was 6.4%, while in 2023 it was 4.1%. The CMD incidence was significantly lower (5.9%) for the improved varieties than it was for the local varieties (35.9%), although the CBSD incidence did not differ significantly between the improved (2.3%) and local varieties (9.7%). Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV) were both detected. Most infections were single CBSV infections (82.9%), followed by single UCBSV (34.3%) and coinfection with both viruses (16.7%). Whiteflies were more abundant in 2023, in which 28% of the fields had super-abundant populations of >100/plant, compared to 5% in 2022. KASP SNP genotyping designated 92.8% of the specimens as SSA-ECA for 2022, while it was 94.4% for 2023. The cassava green mite incidence was 65.4% in 2022 compared to 79.9% in 2023. This study demonstrates that cassava viruses, whiteflies and cassava green mites continue to be important constraints to cassava production in western Kenya, although the widespread cultivation of improved varieties is reducing the impact of cassava viruses. The more widespread application of high-quality seed delivery mechanisms could further enhance the management of these pests/diseases, coupled with wider application of IPM measures for whiteflies and mites. [ABSTRACT FROM AUTHOR]

Huanglongbing (HLB), also known as citrus greening disease, represents a severe and imminent threat to the global citrus industry. With no complete cure currently available, effective control strategies are crucial. This article presents a transmission model of HLB, both with and without nutrient injection, to explore methods for controlling disease spread. By calculating the basic reproduction number ( R 0 ) and analyzing threshold dynamics, we demonstrate that the system remains globally stable when R 0 < 1 , but persists when R 0 > 1 . Sensitivity analyses reveal factors that significantly impact HLB spread on both global and local scales. We also propose a comprehensive optimal control model using the pontryagin minimum principle and validate its feasibility through numerical simulations. Results show that while removing infected trees and spraying insecticides can significantly reduce disease spread, a combination of measures, including the production of disease-free budwood and nursery trees, nutrient solution injection, removal of infected trees, and insecticide application, provides superior control and meets the desired control targets. These findings offer valuable insights for policymakers in understanding and managing HLB outbreaks. [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]

Laryngopharyngeal reflux disease (LPRD) is a common condition affecting patients reporting to an otolaryngologist. However, the diagnosis of this condition is usually hinged on the combination of largely non-specific symptoms, and clinical findings on laryngoscopy. This study aimed at evaluating the utility of digital image analysis to quantitatively evaluate the severity of signs as recorded with laryngoscopy in patients of LPRD. The study group included individuals who were aged between 18 and 65 years and reported to the ENT OPD. These were then divided into two groups depending on symptoms and laryngoscopic findings. The LPRD group had symptomatic patients with an Reflux finding score (RFS) score >7. Those with an RFS of <6 were designated as the 'Normal group'. The Laryngoscopic images were recorded and analyzed using Image J software as per the set protocol. The Red Green Blue (RGB) values of the laryngoscopic images of each group were obtained and subjected to statistical analysis. 200 participants were enrolled in the study with 100 participants in the LPRD group (mean age = 46.2, 40 males, 60 females) and 100 in the control group (mean age = 43.6, 55 males, 45 females). The measured RGB values were more in the LPRD group as compared to the control group and the results were statistically significant (P < 0.001). By providing an objective value to the degree of inflammation, RGB value measurement provides a quick, economical, adaptable tool for auxiliary and corroborative information for the diagnosis of LPRD. [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]

The gene that regulates callose could be modified by CRISPR/Cas9 technology. This research aimed to insert the CRISPR/Cas9-CsCS gene into Ponkan orange genome using Agrobacterium tumefaciens. The explants were soaked in a bacterial suspension for 20 minutes and incubated for 2-3 days. In vitro acceleration growth was conducted with a twofactor completely randomized design. The first factor is the type of explant with three levels (nucellar embryo, zygotic embryo, cotyledon node), and the second factor is the type of media with 6 levels (VMW, MT, MSK0, MSK1, MSK2, MSK3). The results showed of all explant types, the highest plant height average and number of leaves were obtained in a media combination of MS + Kinetin 2 mg L-1, MT, and MS + Kinetin 3 mg L-1. The highest transformation efficiency was in the nucellar embryo explant, while the highest regeneration efficiency was in the zygotic embryo explant. The highest shoot tip grafting percentage was achieved in the cotyledon node explant at 100%. In the grafting phase, the putative transformants before and after artificial bacterial inoculation showed that Ponkan 606 and Ponkan 597 had the highest plant heights, respectively. The intensity of Huanglongbing attacks after bacterial inoculation showed that three genotypes did not show HLB symptoms in the 24th week of observation, namely genotypes 598, 606, and 607. This study concluded that gene transformation in citrus plants produced three genotypes that did not show HLB symptoms. [ABSTRACT FROM AUTHOR]

This article explores the role of the clathrin heavy chain (Chc) protein in the infection of Candidatus Liberibacter asiaticus (CLas) in the Asian citrus psyllid (Diaphorina citri), which is responsible for spreading citrus huanglongbing (HLB). The study found that the DcChc gene, which encodes the Chc protein in D. citri, is upregulated in response to CLas infection. Disrupting the function of DcChc prevented CLas from entering the midgut of D. citri. The article also provides information about the structure and expression patterns of DcChc. The findings suggest that targeting the clathrin-mediated endocytic pathway could potentially be used to control the spread of CLas in the citrus industry. Further research is needed to understand the mechanisms behind the induction of Chc expression during CLas infection. The study was supported by various funding sources in China. [Extracted from the article]

Imidacloprid is a neonicotinoid insecticide used for managing the Asian citrus psyllid, Diaphorina citri Kuwayama, which serves as vector of phytopathogens causing citrus greening. However, development of resistance to neonicotinoids among populations of D. citri has coincided with occasional control failures in the field. The objectives of this research were to (1) survey current levels of imidacloprid resistance in Florida citrus; (2) compare feeding behavior between imidacloprid‐resistant and susceptible D. citri using electrical penetration graph recordings, and (3) investigate the possible amplification of insecticide hormoligosis associated with resistance. Field surveys confirmed that the susceptibility of D. citri populations to imidacloprid has decreased in commercial Florida citrus groves compared with a laboratory‐susceptible population. Following 12 generations of selection, resistance to imidacloprid increased by 438 fold compared with the susceptible strain. Imidacloprid‐susceptible D. citri feeding on citrus exhibited significantly more bouts associated with intercellular pathway (C), phloem penetration (D), phloem salivation (E1), and nonprobing (Np) activities than imidacloprid‐resistant counterparts. However, there were no differences observed in the frequency or duration of phloem ingestion or xylem feeding between susceptible and resistant D. citri. There was no statistical difference in fecundity between resistant and susceptible strains. However, the fecundity of imidacloprid‐susceptible female D. citri treated with a sublethal concentration of imidacloprid (LC25) increased significantly compared with controls, while such hormoligosis was less pronounced among imidacloprid‐resistant psyllids. Our results suggest that imidacloprid‐resistant psyllids may cease feeding sooner than susceptible counterparts following sublethal exposure to this insecticide, indicative of a behavioral resistance mechanism. [ABSTRACT FROM AUTHOR]

Mapping the molecular signatures and metabolic regulation of plant tissues under biotic/abiotic stresses and defensive responses has become a subject of increasing interest in plant biology and systems biology, but determining when and where specialized metabolites are produced and accumulated currently remains a somewhat elusive goal. Herein, we demonstrated the use of a TiO2 nanotube-based composite substrate modified with plasmonic gold nanoparticles and hydrophobic polydopamine (AuNP-hPDA-TDNT) for surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) analysis of a wide range of pesticides and for visualizing the stress-responsive metabolites of citrus leaves during various plant defense processes. This method enabled the visualization of non-uniform and tissue-specific distribution patterns of functional metabolites of citrus leaves that were mechanically damaged, fed to larvae, and infected by Huanglongbing disease. Interestingly, some specialized metabolites exhibited different accumulation and regulation patterns for mechanical damage and larval feeding, suggesting that plant-derived secondary metabolites exercise specific defensive functions with respect to various damage processes. Moreover, the early diagnosis and detection of HLB disease-associated biomarkers can facilitate the prevention of citrus HLB diseases. Overall, this imprinting MS imaging strategy will expand the scope of MS techniques in plant biology, providing more biologically relevant insights into the biosynthesis, accumulation, and defensive role of bioactive metabolites in economically important plants. [ABSTRACT FROM AUTHOR]

The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Psyllidae), is a major pest of citrus due to its role as the vector of the bacterium that causes huanglongbing. In commercial citrus, ACP control currently relies on the application of insecticides, which may not be sustainable long-term, nor practical in urban areas. The sterile insect technique (SIT) is an alternative strategy in which large numbers of pests are reared, sterilized using radiation, and then released into the field to compete with wild individuals for matings, suppressing population growth. As a fundamental step toward the development of SIT for ACP, this study sought to identify the optimum radiation dose required to sterilize ACP without affecting their survival and mating capacity. Virgin adult ACP of both sexes were subjected to doses of X-ray irradiation ranging from 40 to 480 Gy, then paired with a nonirradiated mate and allowed to produce offspring. Fecundity was estimated as the number of eggs laid, and fertility as the proportion of those eggs that hatched. Females were more radio-sensitive than males, exhibiting a major drop in fecundity at even the lowest dose and 100% sterility at 80 Gy. In contrast, a fivefold higher dose (400 Gy) did not achieve complete sterility in males, with around 5% offspring survival. However, F1 progeny of males exposed to 320 Gy or higher were subsequently found to be 100% sterile. This confirmation of inherited sterility suggests that balancing the sterilizing effects of radiation against its mortality-inducing effects may warrant further evaluation. [ABSTRACT FROM AUTHOR]

BACKGROUND: Citrus huanglongbing (HLB) is a devastating disease caused by Candidatus Liberibacter asiaticus (CLas) that affects the citrus industry. In nature, CLas relies primarily on Diaphorina citri Kuwayama as its vector for dissemination. After D. citri ingests CLas‐infected citrus, the pathogen infiltrates the insect's body, where it thrives, reproduces, and exerts regulatory control over the growth and metabolism of D. citri. Previous studies have shown that CLas alters the composition of proteins in the saliva of D. citri, but the functions of these proteins remain largely unknown. RESULTS: In this study, we detected two proteins (DcitSGP1 and DcitSGP3) with high expression levels in CLas‐infected D. citri. Quantitative PCR and Western blotting analysis showed that the two proteins were highly expressed in the salivary glands and delivered into the host plant during feeding. Silencing the two genes significantly decreased the survival rate for D. citri, reduced phloem nutrition sucking and promoted jasmonic acid (JA) defenses in citrus. By contrast, after overexpressing the two genes in citrus, the expression levels of JA pathway‐associated genes decreased. CONCLUSION: Our results suggest that CLas can indirectly suppress the defenses of citrus and support feeding by D. citri via increasing the levels of effectors in the insect's saliva. This discovery facilitates further research into the interaction between insect vectors and pathogens. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Background: With the rapid development of single-cell sequencing technology, histological studies are no longer limited to conventional homogenized tissues. Laser microdissection enables the accurate isolation of specific tissues or cells, and when combined with next-generation sequencing, it can reveal important biological processes at the cellular level. However, traditional laser microdissection techniques have often been complicated and time-consuming, and the quality of the RNA extracted from the collected samples has been inconsistent, limiting follow-up studies. Therefore, an improved, simple, and efficient laser microdissection method is urgently needed. Results: We omitted the sample fixation and cryoprotectant addition steps. Instead, fresh samples were embedded in Optimal Cutting Temperature medium within 1.5 ml centrifuge tube caps, rapidly frozen with liquid nitrogen, and immediately subjected to cryosectioning. A series of section thicknesses of citrus rind were tested for RNA extraction, which showed that 18 μm thickness yielded the highest quality RNA. By shortening the dehydration time to one minute per ethanol gradient and omitting the tissue clearing step, the resulting efficient dehydration and preserved morphology ensured high-quality RNA extraction. We also propose a set of laser microdissection parameters by adjusting the laser power to optimal values, reducing the aperture size, and lowering the pulse frequency. Both the epidermal and subepidermal cells from the citrus rind were collected, and RNA extraction was completed within nine hours. Using this efficient method, the transcriptome sequencing of the isolated tissues generated high-quality data with average Q30 values and mapping rates exceeding 91%. Moreover, the transcriptome analysis revealed significant differences between the cell layers, further confirming the effectiveness of our isolation approach. Conclusions: We developed a simple and rapid laser microdissection method and demonstrated its effectiveness through a study based on citrus rind, from which we generated high-quality transcriptomic data. This fast and efficient method of cell isolation, combined with transcriptome sequencing not only contributes to precise histological studies at the cellular level in citrus but also provides a promising approach for cell-specific transcriptome analysis in a broader range of other plant tissues. [ABSTRACT FROM AUTHOR]

Given the severe impact of Citrus Huanglongbing on orchard production, accurate detection of the disease is crucial in orchard management. In the natural environments, due to factors such as varying light intensities, mutual occlusion of citrus leaves, the extremely small size of Huanglongbing leaves, and the high similarity between Huanglongbing and other citrus diseases, there remains an issue of low detection accuracy when using existing mainstream object detection models for the detection of citrus Huanglongbing. To address this issue, we propose YOLO-EAF (You Only Look Once–Efficient Asymptotic Fusion), an improved model based on YOLOv8n. Firstly, the Efficient Multi-Scale Attention Module with cross-spatial learning (EMA) is integrated into the backbone feature extraction network to enhance the feature extraction and integration capabilities of the model. Secondly, the adaptive spatial feature fusion (ASFF) module is used to enhance the feature fusion ability of different levels of the model so as to improve the generalization ability of the model. Finally, the focal and efficient intersection over union (Focal–EIOU) is utilized as the loss function, which accelerates the convergence process of the model and improves the regression precision and robustness of the model. In order to verify the performance of the YOLO-EAF method, we tested it on the self-built citrus Huanglongbing image dataset. The experimental results showed that YOLO-EAF achieved an 8.4% higher precision than YOLOv8n on the self-built dataset, reaching 82.7%. The F1-score increased by 3.33% to 77.83%, and the mAP (0.5) increased by 3.3% to 84.7%. Through experimental comparisons, the YOLO-EAF model proposed in this paper offers a new technical route for the monitoring and management of Huanglongbing in smart orange orchards. [ABSTRACT FROM AUTHOR]

Huanglongbing, also known as citrus greening, is currently the most devastating citrus disease with limited success in prevention and mitigation. A promising strategy for Huanglongbing control is the use of antimicrobials fused to a carrier protein (phloem protein of 16 kDa or PP16) that targets vascular tissues. This study investigated the effects of genetically modified citrus trees expressing Citrus sinensis PP16 (CsPP16) fused to human lysozyme and β-defensin-2 on the soil microbiome diversity using 16S amplicon analysis. The results indicated that there were no significant alterations in alpha diversity, beta diversity, phylogenetic diversity, differential abundance, or functional prediction between the antimicrobial phloem-overexpressing plants and the control group, suggesting minimal impact on microbial community structure. However, microbiota diversity analysis revealed distinct bacterial assemblages between the rhizosphere soil and root environments. This study helps to understand the ecological implications of crops expressing phloem-targeted antimicrobials for vascular disease management, with minimal impact on soil microbiota. [ABSTRACT FROM AUTHOR]

Diaphorina citri Kuwayama (D. citri) is one of the major pests in the citrus industry, which spreads Citrus Huanglongbing disease. It has developed resistance to chemical insecticides. Therefore, searching for greener solutions for pest management is critically important. The main aim of this study was to evaluate the repellent and insecticidal efficacy of essential oils (EOs) from four species of Myrtaceae plants: Psidium guajava (PG), Eucalyptus robusta (ER), Eucalyptus tereticornis (ET), and Baeckea frutescens (BF) against D. citri and to analyze their chemical compositions. GC-MS analysis was performed, and the results indicated that the EOs of PG, ER, ET, and BF were rich in terpenoids, ketones, esters, and alcohol compounds. The repellent rate of all four EOs showed that it decreased with exposure time but increased with the concentration of EOs from 80.50% to 100.00% after treating D. citri for 6 h with four EOs at 100% concentration and decreased to 67.71% to 85.49% after 24 h of exposure. Among the compounds from the EOs tested, eucalyptol had the strongest repellent activity, with a 24 h repellency rate of 100%. The contact toxicity bioassay results showed that all EOs have insecticidal toxicity to D. citri; the LC50 for nymphs was 36.47–93.15 mL/L, and for adults, it was 60.72–111.00 mL/L. These results show that when PG is used as the reference material, the ER, ET, and BF EOs have strong biological activity against D. citri, which provides a scientific basis for the further development of plant-derived agrochemicals. [ABSTRACT FROM AUTHOR]

Postharvest fibrosis and greening of Toona sinensis buds significantly affect their quality during storage. This study aimed to clarify the effects of low-temperature storage on postharvest red TSB quality harvested in different seasons. Red TSB samples were collected from Guizhou province, China, 21 days after the beginning of spring (Lichun), summer (Lixia), and autumn (Liqiu), and stored at 4 °C in dark conditions. We compared and analyzed the appearance, microstructure, chlorophyll and cellulose content, and expression levels of related genes across different seasons. The results indicated that TSB harvested in spring had a bright, purple-red color, whereas those harvested in summer and autumn were green. All samples lost water and darkened after 1 day of storage. Severe greening occurred in spring-harvested TSB within 3 days, a phenomenon not observed in summer and autumn samples. Microstructural analysis revealed that the cells in the palisade and spongy tissues of spring and autumn TSB settled closely during storage, while summer TSB cells remained loosely aligned. Xylem cells were smallest in spring-harvested TSB and largest in autumn. Prolonged storage led to thickening of the secondary cell walls and pith cell autolysis in the petioles, enlarging the cavity area. Chlorophyll content was higher in leaves than in petioles, while cellulose content was lower in petioles across all seasons. Both chlorophyll and cellulose content increased with storage time. Gene expression analysis showed season-dependent variations and significant increases in the expression of over half of the chlorophyll-related and cellulose-related genes during refrigeration, correlating with the observed changes in chlorophyll and cellulose content. This research provides valuable insights for improving postharvest storage and freshness preservation strategies for red TSB across different seasons. [ABSTRACT FROM AUTHOR]

Brown spot of citrus caused by Alternaria citri is one of the emerging threats to the successful production of citrus crops. The present study, conducted with a substantial sample size of 50 leaf samples for statistical reliability, aimed to determine the change in mineral content in citrus leaves after brown spot disease attack. Leaf samples from a diverse range of susceptible citrus varieties (Valentia late, Washington navel, and Kinnow) and resistant varieties (Citron, Eruka lemon, and Mayer lemon) were analyzed. Significant variations (p ≤ 0.05) in mineral contents were observed across reaction groups (inoculated and un-inoculated), types (resistant and susceptible), and varieties of citrus in response to infection of Alternaria citri. The analysis of variance showed significant changes in mineral levels of citrus leaves, including nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), zinc (Zn), sodium (Na), iron (Fe), and copper (Cu). The results indicate that the concentration of N and P differed by 6.63% and 1.44%, respectively, in resistant plants, while susceptible plants showed a difference of 6.07% and 1.19%. Moreover, resistant plants showed a higher concentrations of K, Ca, Mg, Zn, Na, Fe, and Cu at 8.40, 2.1, 1.83, 2.21, 1.58, 2.89, and 0.36 ppm respectively, compared to susceptible plants which showed concentrations of 5.99, 1.93, 1.47, 1.09, 1.24, 1.81, and 0.31 ppm respectively. Amounts of mineral contents were reduced in both resistant as well as susceptible plants of citrus after inoculation. Amount of N (8.56), P (1.87) % while K (10.74), Ca (2.71), Mg (2.62), Zn (2.20), Na (2.08), Fe (3.57) and Cu (0.20) ppm were recorded in un-inoculated group of citrus plants that reduced to 3.15 and 0.76% and 3.66, 1.40, 0.63,0.42, 0.74, 1.13 and 0.13 ppm in inoculated group respectively. It was accomplished that susceptible varieties contained lower ionic contents than resistant varieties. The higher concentrations of ionic contents in resistant citrus varieties build up the biochemical and physiological processes of the citrus plant, which help to restrict spread of pathogens. Further research could explore the interplay between mineral nutrition and disease resistance in citrus, potentially leading to the development of new disease-resistant varieties. [ABSTRACT FROM AUTHOR]

Targeted precise management of intravascular diseases such as citrus Huanglongbing (HLB) involves the application of therapeutics via trunk injection. Although trunk injection has proven more effective than foliar spray and soil drenching, multiple studies have highlighted limitations for large-scale commercial tree crop applications because of the manual process involved, emphasizing the need for an automated injection system. The design of a trunk injection mechanism to efficiently dispense aqueous therapeutic materials to the trunk of HLB-affected citrus trees requires the characterization of the hydraulic properties of the trunk and the determination of the penetration force of a dispensing needle. This study developed an equation for estimating penetration force at maximum depth based on the needle diameter, depth of penetration, and specific gravity of the wood tissue, and presents a method for estimating injection pump pressure. Trunk hydraulic conductance was measured using a hydraulic conductance flow meter, and needle insertion and removal force were measured using a force gauge in an Instron universal testing machine. The average maximum force was 2517, 3739, and 5387 N for dowel pins 4.76, 6.35, and 7.93 mm in diameter at a 12 mm penetration depth. Average specific conductivity was 2.45, 0.34, and 0.15 kgs-1m-1MPa-1for trunk segments 0-12.7, 12.7-26.7, and 26.7-40.6 cm above the ground, with a corresponding estimated pump pressure of 0.14, 0.99, and 2.31 MPa, respectively. [ABSTRACT FROM AUTHOR]

Simple Summary: Citrus production worldwide is threatened by the bacterium Liberibacter spp. Fagen and its vector Diaphorina citri Kuwayama. In the absence of an effective method against the bacteria, management plans are directed towards the vector. However, management strategies such as chemical control have presented difficulties in controlling the insect. Therefore, the application of new control techniques, such as nanoparticles by green synthesis, emerges as a promising control alternative. To address this issue, the objective of this study was to evaluate silver nanoparticles by green synthesis against D. citri nymphs in the laboratory and greenhouse. The results show that the nanoparticles achieved up to 100% mortality in the laboratory and 80% in the greenhouse. These results demonstrate the effectiveness of silver nanoparticles as a potential control method for the insect. Diaphorina citri Kuwayama (Hemiptera: Liviidae) is a vector of Liberibacter asiaticus Jagoueix et al. and Liberibacter americanus Teixeira et al., causal agents of the critical yellow dragon disease or Huanglongbing (HLB), which affects citrus production worldwide. Recently, green synthetic nanoparticles have emerged as a potential alternative to control of agricultural insect pests. The insecticide effect of silver nanoparticles (AgNPs) on 2nd instar nymphs of D. citri under laboratory and greenhouse conditions was evaluated. Mortality was recorded 24, 48, and 72 h after application on D. citri nymphs under both laboratory and greenhouse conditions. The laboratory results showed that AgNPs caused 97.84 and 100% mortality at 32 and 64 ppm, respectively, 72 h after treatment. In the greenhouse, AgNPs caused 78.69 and 80.14% mortality using 64 and 128 ppm 72 h after application. This research is the first to evaluate the green synthesis AgNPs on D. citri and are a promising strategy to control the pest. [ABSTRACT FROM AUTHOR]

Excessive soil acidity negatively affects citrus growth and development worldwide. However, less information has been presented on its tolerance to low pH stress (LPS). Here, the way in which citrus plants respond to LPS was investigated at morphological, physiological and molecular levels. Under LPS, the root length and diameter were significantly decreased. The malondialdehyde (MDA) and hydrogen peroxide (H2O2) contents and catalase (CAT) activity were significantly enhanced. LPS increased the root indole-3-acetic acid (IAA) and gibberellins (GAs) contents, and leaf chlorophyll content. Additionally, nutrient uptake was significantly affected by LPS. RNA-seq data revealed that a total of 1319 genes responded to LPS, of which 573 and 746 genes were up- and down-regulated, respectively. These differentially expressed genes (DEGs) were mainly linked to carbon metabolism, reactive oxygen species scavenging, nutrient uptake and transport, and hormone synthesis/signalling. Taken together, our data provided an essential foundation for future elucidation of the LPS tolerance of citrus plants. [ABSTRACT FROM AUTHOR]

BACKGROUND: The citrus red mite, Panonychus citri (McGregor) is a globally distributed agricultural pest. Of late, resistance to common acaricides has raised concerns that chemical control of P. citri is an inefficient means of control. Fluralaner, a highly toxic isoxazoline insecticide used to treat various ectoparasites, presents one potential alternative. However, little information has been reported about the effect of fluralaner on the citrus red mite. This study aims to evaluate the toxicity, sublethal and transgenerational effects of fluralaner on P. citri. RESULTS: In both laboratory and field populations of P. citri, we found fluralaner to be more toxic than conventional alternatives, including fenpropathrin, bifenazate, azocyclotin and chlorpyrifos. Interestingly, fluralaner proved more toxic to female adults than to the eggs of P. citri, with median lethal concentrations (LC50) of 2.446 and 122.7 mg L−1, respectively. Exposure to sublethal concentrations of fluralaner (LC10, LC20 and LC30) significantly reduced the fecundity and longevity of female adults P. citri individuals. Although concentrations of fluralaner applied to the parental female adults (F0) led to some changes in the developmental parameters, there were no significant changes in most of the life table parameters or population growth of the F1 generation. CONCLUSION: Our results indicate that fluralaner is highly toxic to P. citri, and a significant sublethal effect on F0 could suppress the population growth of P. citri, but not for F1. Fluralaner may be considered as a pesticide for the future management of the citrus red mite. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Bacterial canker disease caused by Clavibacter michiganensis is a substantial threat to the cultivation of tomatoes, leading to considerable economic losses and global food insecurity. Infection is characterized by white raised lesions on leaves, stem, and fruits with yellow to tan patches between veins, and marginal necrosis. Several agrochemical substances have been reported in previous studies to manage this disease but these were not ecofriendly. Thus present study was designed to control the bacterial canker disease in tomato using green fabricated silver nanoparticles (AgNps). Nanosilver particles (AgNPs) were synthesized utilizing Moringa oleifera leaf extract as a reducing and stabilizing agent. Synthesized AgNPs were characterized using UV–visible spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray (EDX), and Fourier transform infrared spectrometry (FTIR). FTIR showed presence of bioactive compounds in green fabricated AgNPs and UV-visible spectroscopy confirmed the surface plasmon resonance (SPR) band in the range of 350 nm to 355 nm. SEM showed the rectangular segments fused together, and XRD confirmed the crystalline nature of the synthesized AgNPs. The presence of metallic silver ions was confirmed by an EDX detector. Different concentrations (10, 20, 30, and 40 ppm) of the green fabricated AgNPs were exogenously applied on tomato before applying an inoculum of Clavibacter michigensis to record the bacterial canker disease incidence at different day intervals. The optimal concentration of AgNPs was found to be 30 µg/mg that exhibited the most favorable impact on morphological (shoot length, root length, plant fresh and dry weights, root fresh and dry weights) and physiological parameters (chlorophyll contents, membrane stability index, and relative water content) as well as biochemical parameters (proline, total soluble sugar and catalase activity). These findings indicated a noteworthy reduction in biotic stress through the increase of both enzymatic and non-enzymatic activities by the green fabricated AgNPs. This study marks a first biocompatible approach in assessing the potential of green fabricated AgNPs in enhancing the well-being of tomato plants that affected with bacterial canker and establishing an effective management strategy against Clavibacter michiganensis. This is the first study suggests that low concentration of green fabricated nanosilvers (AgNPs) from leaf extract of Moringa oleifera against Clavibacter michiganensis is a promisingly efficient and eco-friendly alternative approach for management of bacterial canker disease in tomato crop. [ABSTRACT FROM AUTHOR]

SUMMARY: Knotted1‐like homeodomain (KNOX) proteins are essential in regulating plant organ differentiation. Land plants, including tomato (Solanum lycopersicum), have two classes of the KNOX protein family, namely, class I (KNOX I) and class II KNOX (KNOX II). While tomato KNOX I proteins are known to stimulate chloroplast development in fruit, affecting fruit coloration, the role of KNOX II proteins in this context remains unclear. In this study, we employ CRISPR/Cas9 to generate knockout mutants of the KNOX II member, SlKN5. These mutants display increased leaf complexity, a phenotype commonly associated with reduced KNOX II activity, as well as enhanced accumulation of chloroplasts and chlorophylls in smaller cells within young, unripe fruit. RNA‐seq data analyses indicate that SlKN5 suppresses the transcriptions of genes involved in chloroplast biogenesis, chlorophyll biosynthesis, and gibberellin catabolism. Furthermore, protein–protein interaction assays reveal that SlKN5 physically interacts with three transcriptional repressors from the BLH1‐clade of BEL1‐like homeodomain (BLH) protein family, SlBLH4, SlBLH5, and SlBLH7, with SlBLH7 showing the strongest interaction. CRISPR/Cas9‐mediated knockout of these SlBLH genes confirmed their overlapping roles in suppressing chloroplast biogenesis, chlorophyll biosynthesis, and lycopene cyclization. Transient assays further demonstrate that the SlKN5–SlBLH7 interaction enhances binding capacity to regulatory regions of key chloroplast‐ and chlorophyll‐related genes, including SlAPRR2‐like1, SlCAB‐1C, and SlGUN4. Collectively, our findings elucidate that the KNOX II SlKN5‐SlBLH regulatory modules serve to inhibit fruit greening and subsequently promote lycopene accumulation, thereby fine‐tuning the color transition from immature green fruit to mature red fruit. Significance Statement: This study shed light on regulatory mechanisms of plastid development in fruits by demonstrating that the class II knotted‐like homeodomain protein SlKN5 negatively regulates chloroplast number and chlorophyll accumulation in tomato fruit development. SlKN5 interacts with BEL1‐like homeodomain protein SlBLH7 and its paralogs to suppress SlAPRR2‐like1 and chlorophyll biosynthetic genes, promoting the developmental shift from growth phase to onset of ripening. This highlights the crucial role of the SlKN5‐BLH module in the regulation of tomato fruit coloration. [ABSTRACT FROM AUTHOR]

Plant pathogens can alter the behavior of their insect vectors as well as their survival and reproduction. The African psyllid, Trioza erytreae, is one of the vectors of Huanglongbing, a citrus disease caused mainly by "Candidatus Liberibacter asiaticus" (CLas). The purpose of this study was to characterize the effects of CLas on the psyllid, T. erytreae using Citrus volkamerina plants as the study system. The study focused more specifically on the CLas effects prior to and after its acquisition by the psyllid T. erytreae. Our results did not support the hypothesis that CLas effects psyllid probing behavior prior to acquisition; few differences were observed between uninfected T. erytrea feeding on CLas‐infected versus control plants. On the other hand, compared to psyllids that had completed their development on control plants, the ones that had completed their development on a CLas‐infected plant exhibited changes in their behavior (greater velocity), physiology (smaller mass) and biochemistry (lower water and lipid content). Altogether, our results confirm the existence of a marked postacquisition effect on the vector locomotor behavior and a minor preacquisition effect of CLas on the vector behavior, which can be partially explained by physiological and biochemical changes. [ABSTRACT FROM AUTHOR]

Entomopathogenic nematodes (EPNs) are an important component of integrated pest management (IPM) strategies; understanding their compatibility with other biocontrol options is of crucial importance in promoting their use. In this study, the toxicity of azadirachtin, sulfoxaflor, spindle oil (Mineral oil), and thyme oil was tested on the survival and pathogenicity of Steinernema carpocapsae (Weiser, 1955) (Rhabditida: Steinernematidae), Steinernema bicornutum sp. n. (Rhabditida: Steinernematidae), Heterorhabditis bacteriophora (Poinar, 1976) (Rhabditida: Heterorhabditidae), and Heterorhabditis indica (Poinar, Karunakar & David, 1992) under controlled conditions (25 ± 1 °C, 60 ± 10% RH). The toxicity of aforementioned agrochemicals to EPNs was evaluated in 12-well plates and the infective juveniles (IJs) of each EPN species (6000 IJs/50 µL ddh2O) were exposed to the recommended field concentrations of agrochemicals. In the pathogenicity tests, the agrochemical and IJs solutions (3000 IJs/ml agrochemical) were applied to potato tubers in plastic containers which contained 20 adults of Planococcus citri (Risso, 1813) (Hemiptera: Pseudococcidae). The survival of IJs and P. citri (Adults) was evaluated daily for three consecutive days after treatment. The results revealed that all tested EPN species were quite compatible with tested agrochemicals and showed survival of over 95% after 72 h of exposure to tested agrochemicals. EPNs and spindle oil combination induced the highest mortality of adult P. citri, and all EPN species caused mortalities over 90% at 72 h after treatment, except for S. bicornotum-spindle oil combination. Additive effects were observed in all combinations of EPNs with agrochemicals except for thyme oil. It appears, therefore, that EPNs applied in combination with azadirachtin, sulfoxaflor, and spindle oil have a great potential for successful control of P. citri. However, further studies are still required to determine the antagonistic or otherwise synergistic effects of tested chemicals on EPNs in controlling P. citri under field conditions. [ABSTRACT FROM AUTHOR]

Simple Summary: Diaphorina citri is an important transmission vector of Candidatus Liberibacter asiaticus (CLas), the causal agent of citrus Huanglongbing (HLB). The control of HLB mainly depends on the management of D. citri. The efficiency of D. citri nymphs in acquiring CLas bacteria is significantly higher than that of the adults, while the transmission efficiency of CLas bacteria by adults is significantly higher than that of nymphs. Therefore, it is of great significance to research the functions of key genes during the molting of fifth-instar nymphs. In this study, SMRT and Illumina sequencing were performed on D. citri fifth-instar nymphs and adults. SMRT-Seq-generated full-length transcripts provide valuable information for improving functional gene research in D. citri. Additionally, Illumina sequencing revealed that the Hippo pathway played an important role in regulating the transition of D. citri from fifth-instar nymphs to adults. Our findings provide useful reference information and lay a foundation for controlling D. citri. Huanglongbing (HLB) is a systemic plant disease caused by 'Candidatus Liberibacter asiaticus (CLas)' and transmitted by Diaphorina citri. D. citri acquires the CLas bacteria in the nymph stage and transmits it in the adult stage, indicating that molting from the nymph to adult stages is crucial for HLB transmission. However, the available D. citri reference genomes are incomplete, and gene function studies have been limited to date. In the current research, PacBio single-molecule real-time (SMRT) and Illumina sequencing were performed to investigate the transcriptome of D. citri nymphs and adults. In total, 10,641 full-length, non-redundant transcripts (FLNRTs), 594 alternative splicing (AS) events, 4522 simple sequence repeats (SSRs), 1086 long-coding RNAs (lncRNAs), 281 transcription factors (TFs), and 4459 APA sites were identified. Furthermore, 3746 differentially expressed genes (DEGs) between nymphs and adults were identified, among which 30 DEGs involved in the Hippo signaling pathway were found. Reverse transcription–quantitative PCR (RT-qPCR) further validated the expression levels of 12 DEGs and showed a positive correlation with transcriptome data. Finally, the spatiotemporal expression pattern of genes involved in the Hippo signaling pathway exhibited high expression in the D. citri testis, ovary, and egg. Silencing of the D. citri transcriptional co-activator (DcYki) gene significantly increased D. citri mortality and decreased the cumulative molting. Our results provide useful information and a reliable data resource for gene function research of D. citri. [ABSTRACT FROM AUTHOR]

Citrus Huanglongbing (HLB) is one of the most serious citrus diseases worldwide, causing huge economic losses every year and seriously affecting the development of the global citrus industry. In Lingnan region of China, HLB threatens the growth of important medicinal plants, such as Citrus reticulata ‘Chachi’, C. grandis ‘Tomentosa’, and C. medica ‘Fingered’. Candidatus Liberibacter asiaticus (CLas) is the most common pathogen, which colonizes the phloem of plants and mainly infects rutaceae citrus species. At present, there is a lack of reports on the successful cultivation of CLas in vitro, making it difficult to study the pathogenic mechanism and control of the disease. Effector (also called effector protein) is a kind of pathogenic factor secreted by pathogens to the host, serving as an important weapon for pathogens to infect plants. The effectors are capable of targeting the key immune signal transduction and regulatory components of host cells, thereby inhibiting plant defense responses and enhancing the pathogenicity of pathogens. CLas can secrete over a hundred effectors, mainly divided into Sec-dependent effectors and non-classical secretory effectors according to different secretion pathways. Among them, there are 90 Sec-dependent effectors and 15 non-classical secretory effectors. They play a key role in the pathogenic process of infecting the host. Studies have shown that HLB effectors could target multiple cellular processes including plant immune signal transduction, autophagy, salicylic acid signaling pathway, and seriously disrupt the host’s defense response to achieve colonization. Combined with recent researches on the pathogenic mechanism of HLB effectors, this article elaborates on the research overview of HLB and the classification of HLB effectors, and summarizes the pathogenic mechanism of effectors that affect citrus defense response. Finally, it offers a prospect on the future research directions, discusses the possibility of searching for important resistance genes to HLB based on identification of effector targets, with a aim to provide guidance for the pathogenic mechanism and disease control of HLB through the study of the effectors. [ABSTRACT FROM AUTHOR]

Up to 32 Colletotrichum species have been reported to be associated with pre‐ or postharvest diseases of citrus globally, while in Australia, six species have been reported to cause citrus leaf and fruit disease. Twig or shoot dieback has recently been observed as an emerging disease in citrus orchards in Western Australia. Colletotrichum species were isolated from diseased twigs showing dieback (withertip) or lesions, with or without gummosis, collected from 12 varieties of orange, mandarin and lemon. Colletotrichum gloeosporioides sensu stricto, Colletotrichum karstii and Colletotrichum novae‐zelandiae were identified using a polyphasic approach that included multigene phylogenetic analysis using sequences of internal transcribed spacer and intervening 5.8S nrDNA (ITS), glyceraldehyde‐3‐phosphate dehydrogenase (gapdh), β‐tubulin (tub2), actin (act) and histone (his3) for isolates in the boninense species complex, and Apn2–Mat1–2 intergenic spacer and partial mating type (Mat1–2) (ApMat) and glutamine synthetase (gs) for isolates in the gloeosporioides species complex, as well as morphological characteristics. C. gloeosporioides was the most prevalent species associated with twig dieback in Western Australia, while C. novae‐zelandiae was reported for the first time in Australia. Pathogenicity tests on shoot twigs from lemon and orange trees confirmed C. gloeosporioides, C. karstii and C. novae‐zelandiae as the cause of twig dieback, with C. gloeosporioides being the most aggressive species. Knowledge of the species causing twig dieback and their lifestyle will assist the development of integrated control methods. [ABSTRACT FROM AUTHOR]

Neohesperidin (hesperetin 7-O-neohesperidoside), a well-known flavanone glycoside widely found in citrus fruits, exhibits a variety of biological activities, with potential applications ranging from food ingredients to therapeutics. The purpose of this manuscript is to provide a comprehensive overview of the chemical, biosynthesis, and pharmacokinetics profiles of neohesperidin, as well as the therapeutic effects and mechanisms of neohesperidin against potential diseases. This literature review covers a wide range of pharmacological responses elicited by Neohesperidin, including neuroprotective, anti-inflammatory, antidiabetic, antimicrobial, and anticancer activities, with a focus on the mechanisms of those pharmacological responses. Additionally, the mechanistic pathways underlying the compound's osteoporosis, antiulcer, cardioprotective, and hepatoprotective effects have been outlined. This review includes detailed illustrations of the biosynthesis, biopharmacokinetics, toxicology, and controlled release of neohesperidine. Neohesperidin demonstrated a broad range of therapeutic and biological activities in the treatment of a variety of complex disorders, including neurodegenerative, hepato-cardiac, cancer, diabetes, obesity, infectious, allergic, and inflammatory diseases. Neohesperidin is a promising therapeutic candidate for the management of various etiologically complex diseases. However, further in vivo and in vitro studies on mechanistic potential are required before clinical trials to confirm the safety, bioavailability, and toxicity profiles of neohesperidin. [ABSTRACT FROM AUTHOR]

This work aimed to isolate, and identify Lactic Acid Bacteria LAB from Egyptian immature citrus honey, and characterize their secondary metabolites, as well as determine the antibacterial activities and transcription of virulence genes (stx1, stx2, and eae) influenced by these bacterial secondary metabolites. From twenty hives, twenty immature citrus bee honey samples were taken. Traditional cultural and biochemical testing were used, followed by molecular confirmation. Further, LAB isolates' antibacterial and cytotoxic properties were investigated. 16S rRNA gene sequencing were assessed and, two lactic acid bacterial isolates were identified as Lactobacillus acidophilus Ch2 and Levilactobacillus brevis Ch1. Both isolates have good antagonistic action against clinical pathogens, with Levilactobacillus brevis Ch1 exhibiting the best antibacterial activity against all indicator pathogens examined. When compared to untreated cancer cells, the isolates demonstrated significant cytotoxic activity. Ch1 and Ch2 cell viability percentages were 39.5% and 18.76%, respectively. Furthermore, when exposed to Levilactobacillus brevis Ch1 metabolites, Shiga-producing Escherichia coli (STEC) virulence gene expression was suppressed. To identify bacterial secondary metabolites, a high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (HPLC-QTOF) approach was developed. Twenty-seven metabolites from diverse chemical classes were discovered in the crude extracts with antibacterial and anticancer characteristics. This is the first thorough investigation on the metabolic profile of LAB isolated from immature Egyptian honey and the findings suggested that isolates or their secondary metabolites could be used in the food sector as medicinal alternatives or as a biocontrol agent. [ABSTRACT FROM AUTHOR]

Citrus Huanglongbing (HLB), caused by the phloem-inhibiting bacterium Candidatus Liberibacter asiaticus (CLas), is the most devastating citrus disease, intimidating citrus production worldwide. Although commercially cultivated citrus cultivars are vulnerable to CLas infection, HLB-tolerant attributes have, however, been observed in certain citrus varieties, suggesting a possible pathway for identifying innate defense regulators that mitigate HLB. By adopting transcriptome and small RNAome analysis, the current study compares the responses of HLB-tolerant lemon (Citrus limon L.) with HLB-susceptible Shatangju mandarin (Citrus reticulata Blanco cv. Shatangju) against CLas infection. Transcriptome analysis revealed significant differences in gene expression between lemon and Shatangju. A total of 1751 and 3076 significantly differentially expressed genes were identified in Shatangju and lemon, respectively. Specifically, CLas infected lemon tissues demonstrated higher expressions of genes involved in antioxidant enzyme activity, protein phosphorylation, carbohydrate, cell wall, and lipid metabolism than Shatangju. Wet-lab experiments further validated these findings, demonstrating increased antioxidant enzyme activity in lemon: APX (35%), SOD (30%), and CAT (64%) than Shatangju. Conversely, Shatangju plants exhibited higher levels of oxidative stress markers like H2O2 (44.5%) and MDA content (65.2%), alongside pronounced ion leakage (11.85%), than lemon. Moreover, microscopic investigations revealed that CLas infected Shatangju phloem exhibits significantly more starch and callose accumulation than lemon. Furthermore, comparative sRNA profiles revealed the potential defensive regulators for HLB tolerance. In Shatangju, increased expression of csi-miR166 suppresses the expression of disease-resistant proteins, leading to inadequate defense against CLas. Conversely, reduced expression of csi-miR166 in lemon plants enables them to combat HLB by activating disease-resistance proteins. The above findings indicate that when infected with CLas, lemon exhibits stronger antioxidative activity and higher expression of disease-resistant genes, contributing to its enhanced tolerance to HLB. In contrast, Shatangju shows lower antioxidative activity, reduced expression of disease-resistant genes, significant ion leakage, and extensive callose deposition, possibly related to damage to plant cell structure and blockage of phloem sieve tubes, thereby promoting the development of HLB symptoms. [ABSTRACT FROM AUTHOR]