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Citrus Huanglongbing (HLB), a highly devastating citrus disease, is associated with 'Candidatus Liberibacter asiacitus' (CLas), a member of phloem-inhabiting α-proteobacteria. HLB can affect all cultivated citrus and no cure is currently available. Previous studies showed that Kaffir lime (Citrus hystrix), primarily grown in South Asia and Southeast Asia, was tolerant to HLB but the molecular mechanism remains unknown. In this study, gene expression profiling experiments were performed on HLB-tolerant C. hystrix and HLB-susceptible C. sinensis three months after inoculation with CLas using RNA-seq data. Differentially expressed genes (DEGs) in the two citrus cultivars were mainly involved in diverse cellular functions including carbohydrate metabolism, photosynthesis, cell wall metabolism, secondary metabolism, hormone metabolism and oxidation/reduction processes. Notably, starch synthesis and photosynthesis process were not disturbed in CLas-infected C. hystrix. Most of the DEGs involved in cell wall metabolism and secondary metabolism were up-regulated in C. hystrix. In addition, the activation of peroxidases, Cu/Zn-SOD and POD4, may also enhance the tolerance of C. hystrix to CLas. This study provides an insight into the host response of HLB-tolerant citrus cultivar to CLas. C. hystrix is potentially useful for HLB-tolerant/resistant citrus breeding in the future.

Background Candidatus Liberibacter asiaticus ( C Las) is the most prevalent pathogen causing the globally prevalent citrus Huanglongbing (HLB). The citrus relative Citrus australasica F. Muell. shows tolerance to HLB. In this study, we grafted HLB-tolerant Ca (C. australasica) and HLB-susceptible Cs ( C. sinensis) Osbeck branches onto healthy C. reticulate Blanco ‘Shatangju’ (SH) and C Las-infected (SI) rootstocks. Results To understand HLB tolerance mechanisms in C. australasica , a comprehensive analysis of transcriptomic and proteomic data of leaves from Ca SH, Ca SI, Cs SH, and Cs SI was conducted. Differentially expressed genes (DEGs) between Ca SI and Ca SH were enriched in acridone alkaloid biosynthesis. In contrast, some DEGs between Cs SI and Cs SH were enriched in plant hormone signal transduction, and MAPK signaling pathway. Several differentially expressed proteins (DEPs) between Ca SI and Ca SH were enriched in phenylpropanoid biosynthesis, whereas several DEPs between Cs SI and Cs SH were enriched in amino acids biosynthesis. In response to C Las infection, several genes involved in amino acid metabolism pathway and citrate cycle pathway showed opposite trends in C. australasica and C. sinensis . Among these genes with opposite expression trends, it is noteworthy that in response to HLB, arogenate/prephenate dehydratase and phenylalanine-4-hydroxylase in phenylalanine and tyrosine biosynthesis remained stable in C. australasica. In addition, glutamate dehydrogenase and amino acid N-acetyltransferase, which are involved in arginine metabolism, were up-regulated in C Las-infected C. australasica . The expression levels of isocitrate dehydrogenase, malate dehydrogenase, and aconitate hydratase, which are involved in the citrate cycle, were higher in Ca SI than in Cs SI. Conclusions These data suggest that the stabilization of phenylalanine biosynthesis and the up-regulation of arginine biosynthesis contribute to HLB-tolerance of C. australasica , and that the changes in enzymes in the citrate cycle pathway and flow of carbon sources to arginine biosynthesis reduce the energy supply for HLB pathogens. These results provide new insights into the mechanism of HLB-tolerance in C. australasica , and provide a theoretical molecular basis for breeding HLB-tolerant citrus varieties.

The accurate identification of citrus fruits is important for fruit yield estimation in complex citrus orchards. In this study, the YOLOv7-tiny-BVP network is constructed based on the YOLOv7-tiny network, with citrus fruits as the research object. This network introduces a BiFormer bilevel routing attention mechanism, which replaces regular convolution with GSConv, adds the VoVGSCSP module to the neck network, and replaces the simplified efficient layer aggregation network (ELAN) with partial convolution (PConv) in the backbone network. The improved model significantly reduces the number of model parameters and the model inference time, while maintaining the network’s high recognition rate for citrus fruits. The results showed that the fruit recognition accuracy of the modified model was 97.9% on the test dataset. Compared with the YOLOv7-tiny, the number of parameters and the size of the improved network were reduced by 38.47% and 4.6 MB, respectively. Moreover, the recognition accuracy, frames per second (FPS), and F1 score improved by 0.9, 2.02, and 1%, respectively. The network model proposed in this paper has an accuracy of 97.9% even after the parameters are reduced by 38.47%, and the model size is only 7.7 MB, which provides a new idea for the development of a lightweight target detection model.

Obligate fungal pathogens (ascomycetes and basidiomycetes) and oomycetes are known to cause diseases in cereal crop plants. They feed on living cells and most of them have learned to bypass the host immune machinery. This paper discusses some of the factors that are associated with pathogenicity drawing examples from ascomycetes, basidiomycetes and oomycetes, with respect to their manifestation in crop plants. The comparisons have revealed a striking similarity in the three groups suggesting convergent pathways that have arisen from three lineages independently leading to an obligate lifestyle. This review has been written with the intent, that new information on adaptation strategies of biotrophs, modifications in pathogenicity strategies and population dynamics will improve current strategies for breeding with stable resistance.

Zebra Chip (ZC) is an emerging plant disease that causes aboveground decline of potato shoots and generally results in unusable tubers. This disease has led to multi-million dollar losses for growers in the central and western United States over the past decade and impacts the livelihood of potato farmers in Mexico and New Zealand. ZC is associated with ‘ Candidatus Liberibacter solanacearum’, a fastidious alpha-proteobacterium that is transmitted by a phloem-feeding psyllid vector, Bactericera cockerelli Sulc. Research on this disease has been hampered by a lack of robust culture methods and paucity of genome sequence information for ‘ Ca. L. solanacearum’. Here we present the sequence of the 1.26 Mbp metagenome of ‘ Ca. L. solanacearum’, based on DNA isolated from potato psyllids. The coding inventory of the ‘ Ca. L. solanacearum’ genome was analyzed and compared to related Rhizobiaceae to better understand ‘ Ca. L. solanacearum’ physiology and identify potential targets to develop improved treatment strategies. This analysis revealed a number of unique transporters and pathways, all potentially contributing to ZC pathogenesis. Some of these factors may have been acquired through horizontal gene transfer. Taxonomically, ‘ Ca. L. solanacearum’ is related to ‘ Ca. L. asiaticus’, a suspected causative agent of citrus huanglongbing, yet many genome rearrangements and several gene gains/losses are evident when comparing these two Liberibacter. species. Relative to ‘ Ca. L. asiaticus’, ‘ Ca. L. solanacearum’ probably has reduced capacity for nucleic acid modification, increased amino acid and vitamin biosynthesis functionalities, and gained a high-affinity iron transport system characteristic of several pathogenic microbes.

Citrus Huanglongbing (HLB) is one of the most devastating diseases in the citrus industry and is caused primarily by ‘ Candidatus Liberibacter asiaticus’ ( C Las), a phloem-restricted gram-negative bacterium transmitted via citrus psyllids in the field. Precise C Las detection is crucial for HLB control, particularly during extensive surveys in new emerging regions. Unfortunately, the lack of a practical on-site detection method for C Las due to the limited specificity of immunostrips and the costive non-user friendliness approaches prevent the effective disease control. In this study, a probe-based recombinase polymerase amplification (RPA) targeting the C Las five-copy nrd B gene (β-subunit of ribonucleotide reductase, RNR) was developed and evaluated for its specificity, sensitivity, and reliability. To enhance user-friendliness and facilitate widely use, an All-in-one kit was premade as freeze-dried pellets in individual tubes, containing all necessary components except DNA template. The applicability of the All-in-one kit for C Las detection was confirmed using plant or psyllid crude DNA extracts. Collectively, the All-in-one kit offers a specific, sensitive, rapid, cost-effective, and practical alternative for diagnosing C Las in field conditions when coupled with simplified crude DNA extraction method, providing an alternative approach for on-site C Las detection in the context of HLB.

The 40S ribosomal protein SA (RPSA) functions as an important regulatory factor in plant resistance to abiotic stresses. However, the role of RPSA in response to plant virus infection is poorly understood. Citrus yellow vein clearing virus (CYVCV) has a significantly negative impact on citrus production, and its coat protein (CP) is involved in viral pathogenicity. In this study, we revealed the interaction of CP with Eureka lemon 40S RPSA (ClRPSA-2) in the nucleus, membrane, and endoplasmic reticulum of Nicotiana benthamiana . Further experiments demonstrated that the ClRPSA-2 N-terminal conserved region (amino acids 22—122) was involved in the interaction with CP, and the ClRPSA-2 expression in young Eureka lemon leaves significantly reduced. Transient expression of ClRPSA-2 triggered the expression of jasmonic acid (JA), photosynthetic pathway- and resistance-related genes, as well as increased the JA content and maximum photochemical efficiency ( Fv/Fm ) in lemon. Furthermore, ClRPSA-2 negatively regulated CYVCV resistance in plants, which induced resistance to other citrus viruses. These findings enhance our understanding of the interaction between CYVCV and citrus plants and provide a basis for future research on resistance breeding of citrus.

[...]summer is often accompanied by strong convection weather such as heavy rain, and the erosion of heavy rain will also reduce the population density. [...]when a single tree is damaged by P. citri, the entire orchard will soon be damaged1101. After the ecological balance of an orchards is destroyed, the damage of P. citri, which lost the control of natural enemies, becomes more rampant, trapping in a vicious cycle1131. 2.4 Chemical control factor At present, chemical control is still the major measure against P. citri, but because of its small size, rapid reproduction, short generation cycle and unique reproductive mode, it brings many difficulties to chemical control. In addition to effectively reducing the initial quantity of mite population through winter orchard clearing, the early peak period of spring and autumn is the key period for chemical control in the growth season. 3.1 Chemical control Chemical control has the advantages of high efficiency, convenience and low relative cost1161.

Autophagy, one of the most widespread and highly conserved protein degradation systems in eukaryotic cells, plays an important role in plant growth, development and stress response. Beclin 1 is a core component of the phosphatidylinositol 3‐kinase (PI3K) autophagy complex and positively regulates plant immunity against viruses. The upregulation of Eureka lemon ClBeclin1 was observed in response to citrus yellow vein clearing virus (CYVCV) infection. However, the function of ClBeclin1 and the underlying mechanism during CYVCV colonisation remain unclear. Here, the resistance evaluation of the overexpression and silencing of ClBeclin1 in Eureka lemon hairy roots revealed it as a positive regulator of citrus immunity against CYVCV. Transcriptomic profiling and metabolic analyses along with genetic evidence implied that the overexpression of ClBeclin1 positively triggered reactive oxygen species (ROS)‐ and jasmonic acid (JA)‐mediated immunity in citrus. The accumulation of ROS and JA contents was attributed to the autophagic degradation of the ROS scavenger ClAPX1 via ClBeclin1 overexpression. Exogenous application of either H2O2 or JA significantly reduced CYVCV colonisation and vein‐clearing symptoms on the host. Collectively, our findings indicate that ClBeclin1 activation contributes to citrus immunity against CYVCV through triggering ROS‐ and JA‐mediated defence responses, and the accumulation of ROS and JA resulted from the autophagic degradation of ClAPX1 by ClBeclin1. During citrus yellow vein clearing virus infection, ClBeclin1 targets ClAPX1 for degradation through autophagy pathway to promote reactive oxygen species and jasmonic acid production, enhancing disease resistance in Eureka lemon.

The damage of T. urticae in China was first reported in the 1980s. Since 1990, T. urticae has caused serious damage in apple producing areas in China, and the damage has further spread and aggravated, resulting in huge economic losses[7] . First of all, weeds should be uprooted on the edge of the field regularly, and the residual plants and leaves should be removed to reduce the environment and places suitable for the survival of T. urticae. [...]starting from the optimum temperature and humidity, too low or too high temperature and too high relative humidity is not conducive to the growth, development and reproduction of T. urticae. [...]in the actual production process, it can effectively inhibit the growth, development and reproduction of T. urticae by more watering and irrigation to maintain the relative humidity in the environment. In recent years, acaricides have been developed to the direction of heterocyclic acaricides that inhibit the respiratory metabolism of mites[27]. [...]while paying attention to the development of new agents, chemical control should also pay close attention to the dynamic change of the resistance of harmful mites to existing acaricides.