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The cultivation of citrus in the Mediterranean region is of considerable economic importance. The viability of this industry is contingent upon a number of factors, with adequate phytosanitary management being of particular significance. During the last decade, the geographical range of the invasive psyllid, Trioza erytreae (Del Guercio, 1918), has expanded to the mainland territories of Portugal and Spain. Trioza erytreae acts as a vector for the Huanglongbing disease (HLB). This review presents the current knowledge about the hosts of the psyllid and their attractiveness and suitability. A classification of the hosts according to their suitability, as assessed in the literature, is provided. The attributes of the hosts and the methods used to assess their suitability are described, as well as the climatic factors that affect the psyllid–host interaction. The review emphasises the importance of a comprehensive evaluation of the interactions between the psyllids and their hosts to develop and implement more effective strategies for controlling T. erytreae. [ABSTRACT FROM AUTHOR]

Zebra chip is an increasingly serious disease in commercial potato production globally. Resistance can be pursued by control of the insect vector, the tomato-potato psyllid, Bactericera cockerelli or the bacterial causal agent, Candidatus Liberibacter solanacearum (Lso). Some Lso-infected plants of the wild potato species S. microdontum (mcd) had been observed to have low symptom expression. Thus, we evaluated a representative core collection of 86 individuals from 50 mcd populations in the US Potato Genebank (USPG). Real-time quantitative PCR on tissue from infected leaves was used as a proxy for bacterial titer of Lso. Russet Burbank control had 56% of the MLT of the most susceptible mcd individual. The average for all mcd was 67%, and the lowest, most resistant six mcd individuals were 0%. Repeated testing of those six individuals identified two as most reliably resistant: mcd15B2 from PI 265575 and mcd62B1 from PI 498126. All of these mcd individuals are available from USPG. They should be useful for research and breeding aimed at better understanding and controlling Zebra chip disease. [ABSTRACT FROM AUTHOR]

Abstract This study is the first to investigate the presence and movement of the novel Liberibacter species ‘Candidatus Liberibacter brunswickensis’ (CLbr) in eggplant, Solanum melongena. The psyllid, Acizzia solanicola can transmit CLbr to eggplant and CLbr can be acquired by CLbr-negative A. solanicola individuals from CLbr-positive eggplants. In planta, CLbr can replicate, move and persist. Investigation into the early development of eggplants showed that CLbr titres had increased at the inoculation site at 14 days post inoculation access period (DPIAP). CLbr had become systemic in the majority of plants tested by 28 DPIAP. The highest bacterial titres were recorded at 35 DPIAP in all samples of the inoculated leaf, the roots, stems and the midrib and petiole samples of the newest leaf (the top leaf). This finding strongly suggests that CLbr movement in planta follows the source to sink relationship as previously described for ‘Ca. Liberibacter asiaticus’ (CLas) and ‘Ca. Liberibacter solanacearum’ (CLso). No symptoms consistent with Liberibacter-associated diseases were noted for plants colonised by CLbr during this study, consistent with the hypothesis that CLbr does not cause disease of eggplant during the early stages of host colonisation. In addition, no significant differences in biomass were found between eggplant colonised with CLbr, compared to those that were exposed to CLbr-negative A. solanicola, and to control plants.

São Paulo, Brazil, and Florida, USA, were the two major orange production areas in the world until Huanglongbing (HLB) was discovered in São Paulo in 2004 and Florida in 2005. In the absence of resistant citrus varieties, HLB is the most destructive citrus disease known because of the lack of effective tools to reduce spread of the vector, Diaphorina citri (Asian citrus psyllid), and transmission of the associated pathogen, Candidatus Liberibacter asiaticus. In both countries, a three-pronged management approach was recommended and begun: planting only disease-free nursery trees, effective psyllid control, and removal of all symptomatic trees. In Brazil, these management procedures were continued and improved and resulted in relatively little overall loss of production. In contrast, in Florida the citrus industry has been devastated with annual production reduced by approximately 80%. This review compares and contrasts various cultural and pest management strategies that have been used to reduce infection by the pathogen and increase tolerance of HLB in the main orange-growing regions in the world. [ABSTRACT FROM AUTHOR]

This study is the first to investigate the presence and movement of the novel Liberibacter species 'Candidatus Liberibacter brunswickensis' (CLbr) in eggplant, Solanum melongena. The psyllid, Acizzia solanicola can transmit CLbr to eggplant and CLbr can be acquired by CLbr-negative A. solanicola individuals from CLbr-positive eggplants. In planta, CLbr can replicate, move and persist. Investigation into the early development of eggplants showed that CLbr titres had increased at the inoculation site at 14 days post inoculation access period (DPIAP). CLbr had become systemic in the majority of plants tested by 28 DPIAP. The highest bacterial titres were recorded at 35 DPIAP in all samples of the inoculated leaf, the roots, stems and the midrib and petiole samples of the newest leaf (the top leaf). This finding strongly suggests that CLbr movement in planta follows the source to sink relationship as previously described for 'Ca. Liberibacter asiaticus' (CLas) and 'Ca. Liberibacter solanacearum' (CLso). No symptoms consistent with Liberibacter-associated diseases were noted for plants colonised by CLbr during this study, consistent with the hypothesis that CLbr does not cause disease of eggplant during the early stages of host colonisation. In addition, no significant differences in biomass were found between eggplant colonised with CLbr, compared to those that were exposed to CLbr-negative A. solanicola, and to control plants. [ABSTRACT FROM AUTHOR]

The cultivation of citrus in the Mediterranean region is of considerable economic importance. The viability of this industry is contingent upon a number of factors, with adequate phytosanitary management being of particular significance. During the last decade, the geographical range of the invasive psyllid, Trioza erytreae (Del Guercio, 1918), has expanded to the mainland territories of Portugal and Spain. Trioza erytreae acts as a vector for the Huanglongbing disease (HLB). This review presents the current knowledge about the hosts of the psyllid and their attractiveness and suitability. A classification of the hosts according to their suitability, as assessed in the literature, is provided. The attributes of the hosts and the methods used to assess their suitability are described, as well as the climatic factors that affect the psyllid–host interaction. The review emphasises the importance of a comprehensive evaluation of the interactions between the psyllids and their hosts to develop and implement more effective strategies for controlling T. erytreae.

Psyllids feed exclusively on plant sap, which is an unbalanced diet for herbivores due to its low nitrogen content. Therefore, the plant-psyllid-natural enemy interactions can be strongly shaped by the bottom-up forces of N fertilization. Pear psylla Cacopsylla chinensis is a notorious pest in East Asian countries, inflicting devastating damage to pear trees and fruits. However, the bottom-up effects of nitrogen fertilizer on C. chinensis and the mechanisms remain unexplored. Here, we evaluated the performance of C. chinensis larvae over the N application range of 0–1500 mg/kg. The feeding activity and body weight of C. chinensis increased and the developmental duration of C. chinensis decreased significantly when N application increased. Our results indicated that nitrogen application enhanced psyllid fitness on host plant. By analyzing pear leaf metabolites, we found that only ferulic acid increased with the increase of nitrogen fertilizer concentration among phenolics assessed. Exogenously application of ferulic acid accelerated the development of psyllid nymphs. We also found that the concentration of both essential and non-essential amino acids increased significantly when N supply increased, which provided C. chinensis with increased nutrients for their development. The expression levels of several C. chinensis genes in the amino acids synthesis pathway decreased significantly after nitrogen application, indicating that C. chinensis can adjust its amino acid synthesis levels based on its diet. We demonstrated that the enhanced fitness of psyllids under nitrogen supply stems from altered host chemical traits and nutritional quality. The manipulation of nitrogen fertilization has a high potential for use in psyllid IPM programs by reducing psyllid performance. [ABSTRACT FROM AUTHOR]

ABSTRACT The ‘Tahiti’ acid lime and orange trees are hosts of ‘Candidatus Liberibacter asiaticus’ (CLas), the pathogen associated with the severe Asian form of huanglongbing (HLB), the most devasting citrus disease. They are also hosts of the vector of CLas, the Asian citrus psyllid (ACP) Diaphorina citri Kuwayama. Relatively small numbers of lime trees occur in gardens and small orchards near large commercial ‘Valencia’ sweet orange orchards in Brazil. Applications of insecticides to suppress populations of ACP on the lime trees are usually nil or less frequent than in the orange orchards. Abundance of the psyllid on lime trees may therefore increase the risk of CLas spreading to the orchards. Because the abundance of the psyllid is influenced by the suitability of the trees as hosts, we compared reproductive potential of the insect on the two hosts in a controlled environment chamber (CEC) and in a greenhouse (GH). Daily temperature and relative humidity averaged 22ºC and 60% inside the CEC and 24°C and 70% inside the GH. Two pairs of adult male and female psyllids were caged for 3 days on new shoots and the fecundity and durations of development and survival of eggs and nymphs evaluated. Overall, acid ‘Tahiti’ was 3.5 times less suitable to ACP than ‘Valencia’. Fecundity and survival of nymphs were 27% and 59% lower, and the life cycle 34% longer on ‘Tahiti’ than on ‘Valencia’. Potential impacts of the results on CLas spread and HLB control are discussed.

Diaphorina citri , also known as the Asian citrus psyllid, is the main vector of ' Candidatus Liberibacter asiaticus ' (CLas) associated with citrus Huanglongbing. It has been reported that D. citri could also be infected by Citrus tristeza virus (CTV), a virus that has been previously reported to be vectored by certain aphid species. In this study, the CTV and CLas profiles in different organs, color variants, developmental stages, or sexes of D. citri insects were analyzed. Although no significant differences were found between nymphs and adults in CTV titers, we found that the third instar nymph of D. citri was more efficient in CTV and CLas acquisition compared to the fourth and fifth instars and adults. With the instars of D. citri development, the relationship between the acquiring of CTV and CLas by D. citri seemed to follow an inverse trend, with the titer of CLas increased and the titer of CTV decreased. No significant differences were observed between the 2 sexes of D. citri in acquiring either CTV or CLas titers in the field. However, no differences were drawn among the 3 color morph variants for CTV titers. CTV titers in the midguts of adult D. citri were significantly higher than those in the salivary glands. Both CTV-positive incidence and CTV titers in the midguts of adult D. citri increased with increasing exposure periods. This study provides new data to deepen our understanding of the CTV-involved interaction between D. citri and CLas. [ABSTRACT FROM AUTHOR]

Sap-feeding insects in the order Hemiptera associate with obligate endosymbionts that are required for survival and facultative endosymbionts that can potentially modify resistance to stress, enemies, development, and reproduction. In the superfamily Psylloidea, the jumping plant lice (psyllids), less is known about the diversity and prevalence of their endosymbionts compared to other sap-feeding pests such as aphids (Aphididae). To address this knowledge gap, using 16S rRNA sequencing we identify symbionts across divergent psyllid host lineages from around the world. Taking advantage of a new comprehensive phylogenomic analyses of Psylloidea, we included psyllid samples from 44 species of 35 genera of five families, collected from 11 international locations for this study. Across psyllid lineages, a total of 91 OTUs were recovered, predominantly of the Enterobacteriaceae (68%). The diversity of endosymbionts harbored by each psyllid species was low with an average of approximately 3 OTUs. Two clades of endosymbionts (clade 1 and 2), belonging to Enterobacteriaceae, were identified that appear to be long term endosymbionts of the psyllid families Triozidae and Psyllidae, respectively. We also conducted high throughput metagenomic sequencing on three Ca. Liberibacter infected psyllid species (Russelliana capsici, Trichochermes walkeri, and Macrohomotoma gladiata), initially identified from 16S rRNA sequencing, to obtain more genomic information on these putative Liberibacter plant pathogens. The phylogenomic analyses from these data identified a new Ca. Liberibacter species, Candidatus Liberibacter capsica, that is a potential pathogen of solanaceous crops. This new species shares a distant ancestor with Ca. L. americanus, which occurs in the same range as R. capsici in South America. We also detected the first association between a psyllid specializing on woody hosts and the Liberibacter species Ca. L. psyllaurous, which is a globally distributed pathogen of herbaceous crop hosts in the Solanaceae. Finally, we detected a potential association between a psyllid pest of figs (M. gladiata) and a Ca. Liberibacter related to Ca. L. asiaticus, which causes severe disease in citrus. Our findings reveal a wider diversity of associations between facultative symbionts and psyllids than previously reported and suggest numerous avenues for future work to clarify novel associations of ecological, evolutionary, and pathogenic interest.

A field investigation was carried out to evaluate the efficacy of certain biopesticides and chemical insecticides against the major sucking pests of curry leaf, Murraya koenigii (L.) Spreng. in the Neyyattinkara region of Thiruvananthapuram district in Kerala, India during September 2022. Among the treatments evaluated, neem garlic soap formulation-KAU Raksha and talc-based formulation of Lecanicilium lecanii were proved effective in reducing the psyllids, Diaphorina citri population by 65 and 58.17 per cent. Further, Horticultural Mineral Oil and talc-based formulations of L. lecanii were effective in reducing the mite Schizotetranychus baltazari population by 39.18 and 33.44 per cent, respectively. Whitefly, Aleuroclava complex was effectively managed by talc-based formulation of L. lecanii with a per cent efficacy of75.23, which was on par with chemical management. Among the chemical insecticides, chlorantraniliprole 8.8 % w/w + thiamethoxam 17.5 % w/w SC reduced psyllid, mite and whitefly populations by 89.91, 49.76 and 76.63 per cent, respectively, over untreated control. The study highlighted the effectiveness of some biopesticides, which can be utilized for the organic pest management of sucking pests of curry leaf. [ABSTRACT FROM AUTHOR]

Background: The psyllid, Bactericera cockerelli, is an insect vector of 'Candidatus Liberibacter' causing "Zebra chip" disease that affects potato and other Solanaceae crops worldwide. In the present study, we analyzed the bacterial communities associated with the insect vector Bactericera cockerelli central haplotype of tomato crop fields in four regions from Mexico. Methods: PCR was used to amplify the mitochondrial cytochrome oxidase I gene (mtCOI) and then analyze the single nucleotide polymorphisms (SNP) and phylogenetic analysis for haplotype identification of the isolated B. cockerelli. Moreover, we carried out the microbial diversity analysis of several B. cockerelli collected from four regions of Mexico through the NGS sequencing of 16S rRNA V3 region. Finally, Wolbachia was detected by the wsp gene PCR amplification, which is the B. cockerelli facultative symbiont. Also we were able to confirm the relationship with several Wolbachia strains by phylogenetic analysis. Results: Our results pointed that B. cockerelli collected in the four locations from Mexico (Central Mexico: Queretaro, and Northern Mexico: Sinaloa, Coahuila, and Nuevo Leon) were identified, such as the central haplotype. Analyses of the parameters of the composition, relative abundance, and diversity (Shannon index: 1.328 ± 0.472; Simpson index 0.582 ± 0.167), showing a notably relatively few microbial species in B. cockerelli. Analyses identified various facultative symbionts, particularly the Wolbachia (Rickettsiales: Anaplasmataceae) with a relative abundance higher. In contrast, the genera of Sodalis and 'Candidatus Carsonella' (Gammaproteobacteria: Oceanospirillales: Halomonadaceae) were identified with a relatively low abundance. On the other hand, the relative abundance for the genus 'Candidatus Liberibacter' was higher only for some of the locations analyzed. PCR amplification of a fragment of the gene encoding a surface protein (wsp) of Wolbachia and phylogenetic analysis corroborated the presence of this bacterium in the central haplotype. Beta-diversity analysis revealed that the presence of the genus 'Candidatus Liberibacter' influences the microbiota structure of this psyllid species. Conclusions: Our data support that the members with the highest representation in microbial community of B. cockerelli central haplotype, comprise their obligate symbiont, Carsonella, and facultative symbionts. We also found evidence that among the factors analyzed, the presence of the plant pathogen affects the structure and composition of the bacterial community associated with B. cockerelli. [ABSTRACT FROM AUTHOR]

Phoresy is one of the most distinctive relationships between mites and insects, and the off-host interaction between phoretic mites and their carriers is the most critical factor sustaining the phoretic association. As phoretic associations commonly occur in temporary habitats, little is known about off-host interactions between phoronts and carriers. However, an off-host interaction has been reported, in which the plant-mediated competition between a phoretic gall mite, Aceria pallida, and its psyllid vector, Bactericera gobica, after detachment decreases leaf abscission caused by B. gobica and then directly facilitates their phoretic association. In this obligate phoresy, A. pallida seasonally attaches to B. gobica for overwinter survival and they share the same host plant, Lycium barbarum, during the growing season. It is unknown how the host plant responds to these two herbivores and what plant metabolites are involved in their interspecific interaction. Here, effects of A. pallida and B. gobica on the host plant's transcriptome and metabolome, and on enzymes involved in plant defence, at various infestation stages were studied by inoculating A. pallida and B. gobica either separately or simultaneously on leaves of L. barbarum. Our results showed that (a) A. pallida significantly promoted primary and secondary metabolite accumulation, (b) B. gobica markedly inhibited primary and secondary metabolite accumulation and had little influence on defence enzyme activity, and (c) under simultaneous A. pallida and B. gobica infestation, an intermediate response was predicted. These findings indicate that A. pallida and B. gobica have different effects on host plants, A. pallida inhibits B. gobica mainly by increasing the secondary metabolism of L. barbarum, whereas B. gobica inhibits A. pallida mainly by decreasing the primary metabolism of L. barbarum. In conjunction with our previous research, we speculate that this trade-off in host plant metabolite response between A. pallida and B. gobica after detachment promotes a stable phoretic association. [ABSTRACT FROM AUTHOR]

The carrot psyllid, Bactericera trigonica, is a vector of 'Candidatus Liberibacter solanacearum' which infects carrots and many of solanaceous plants. The psyllid was first reported in Spain, then it was rapidly spreading throughout the Mediterranean countries, where it causes considerable damages to carrot crops. To minimize the spread of psyllid species as well as the associated fastidious bacteria, field inspections have been carried out in order to seek for a natural enemies of B. trigonica. Field surveys revealed the presence of a new eulophid parasitoid for the first time in Tunisia attacking larvae of B. trigonica, the main responsible for the significant losses in carrot fields. In order to study the parasitism rate of this parasitoid, a weekly sampling of carrot plants carrying the psyllids and its parasitoids was performed in carrot fields. The parasitism rate and the preferential stage for this parasitoid were also determined under laboratory conditions. The result shows Tamarixia pronomus, preferred late (4th and 5th) instar larvae to early (2nd and 3rd) instar larvae of B. trigonica. There, the parasitism average of late instars was estimated to average 80% and approached 100%. It should be noted that parasitism rates varied by season, with the spring showing the highest averages. Further efforts are warranted to enhance the biological control of B. trigonica and thereby reduce psyllid populations and the spread of 'Candidatus Liberibacter solanacearum'. [ABSTRACT FROM AUTHOR]

Psyllaephagus malloticolae Rawat & Kumar sp. nov. a parasitoid of Trioza malloticola (Crawford) (Hemiptera, Psylloidea, Triozidae) causing galls on leaves of the Kamala tree, Mallotus philippensis Muell, 1865 is described from India. An updated key to all the known allied species of Psyllaephagus Ashmead from India is also provided. The new species comes close to P. garuga Sudhir & Singh, 2011 but differs from it in having Funicular V the longest segment, mid-tibial spur longer than basitarsus, and the exserted ovipositor sheath.

Background The psyllid, Bactericera cockerelli, is an insect vector of ‘Candidatus Liberibacter’ causing “Zebra chip” disease that affects potato and other Solanaceae crops worldwide. In the present study, we analyzed the bacterial communities associated with the insect vector Bactericera cockerelli central haplotype of tomato crop fields in four regions from Mexico. Methods PCR was used to amplify the mitochondrial cytochrome oxidase I gene (mtCOI) and then analyze the single nucleotide polymorphisms (SNP) and phylogenetic analysis for haplotype identification of the isolated B. cockerelli. Moreover, we carried out the microbial diversity analysis of several B. cockerelli collected from four regions of Mexico through the NGS sequencing of 16S rRNA V3 region. Finally, Wolbachia was detected by the wsp gene PCR amplification, which is the B. cockerelli facultative symbiont. Also we were able to confirm the relationship with several Wolbachia strains by phylogenetic analysis. Results Our results pointed that B. cockerelli collected in the four locations from Mexico (Central Mexico: Queretaro, and Northern Mexico: Sinaloa, Coahuila, and Nuevo Leon) were identified, such as the central haplotype. Analyses of the parameters of the composition, relative abundance, and diversity (Shannon index: 1.328 ± 0.472; Simpson index 0.582 ± 0.167), showing a notably relatively few microbial species in B. cockerelli. Analyses identified various facultative symbionts, particularly the Wolbachia (Rickettsiales: Anaplasmataceae) with a relative abundance higher. In contrast, the genera of Sodalis and ‘Candidatus Carsonella’ (Gammaproteobacteria: Oceanospirillales: Halomonadaceae) were identified with a relatively low abundance. On the other hand, the relative abundance for the genus ‘Candidatus Liberibacter’ was higher only for some of the locations analyzed. PCR amplification of a fragment of the gene encoding a surface protein (wsp) of Wolbachia and phylogenetic analysis corroborated the presence of this bacterium in the central haplotype. Beta-diversity analysis revealed that the presence of the genus ‘Candidatus Liberibacter’ influences the microbiota structure of this psyllid species. Conclusions Our data support that the members with the highest representation in microbial community of B. cockerelli central haplotype, comprise their obligate symbiont, Carsonella, and facultative symbionts. We also found evidence that among the factors analyzed, the presence of the plant pathogen affects the structure and composition of the bacterial community associated with B. cockerelli.

‘Candidatus Liberibacter solanacearum’ (Lso) is a phloem-limited pathogen associated with devastating diseases in members of the Solanaceae and Apiaceae and vectored by several psyllid species. Different Lso haplotypes have been identified, and LsoA and LsoB are responsible for diseases in Solanaceae crops. Our efforts are aimed at identifying pathogenicity factors used by this bacterium to thrive in different hosts. Bacterial secreted proteins can play a role in host colonization or the manipulation of the host immune responses; these proteins are called effectors. In this study, we identified six LsoB-specific proteins with a conserved secretion motif as well as a conserved N-terminal domain in the mature protein. These proteins had different expression and secretion patterns but a similar subcellular localization in Nicotiana benthamiana leaves, suggesting that they play different roles regardless of their conserved secretion motif. One of these proteins, CKC_04425, was expressed at high levels in the insect vector and the host plant, indicating that it could play a role in both the plant and insect hosts, whereas the others were mainly expressed in the plant. One protein, CKC_05701, was able to efficiently suppress programmed cell death and reactive oxygen species production, suggesting that it may have a virulence role in LsoB-specific pathogenesis. [ABSTRACT FROM AUTHOR]

Psyllid yellows, vein-greening (VG), and zebra chip (ZC) diseases, which are primarily transmitted by potato psyllid (PoP) carrying Candidatus Liberibacter solanacearum (CLso), have caused significant losses in solanaceous crop production worldwide. Pathogens interact with their vectors at the organic and cellular levels, while the potential changes that may occur at the biochemical level are less well reported. In this study, the impact of CLso on the metabolism of PoP and the identification of biomarkers from infected psyllids were examined. Using ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) analysis, metabolomic changes in CLso-infected psyllids were compared to uninfected ones. A total of 34 metabolites were identified as potential biomarkers of CLso infection, which were primarily related to amino acid, carbohydrate, and lipid metabolism. The significant increase in glycerophospholipids is thought to be associated with CLso evading the insect vector's immune defense. Matrix-assisted Laser Desorption Ionization Mass Spectrometry Imaging (MALDI-MSI) was used to map the spatial distribution of these biomarkers, revealing that 15-keto-Prostaglandin E2 and alpha-D-Glucose were highly expressed in the abdomen of uninfected psyllids but down-regulated in infected psyllids. It is speculated that this down-regulation may be due to CLso evading surveillance by immune suppression in the PoP midgut. Overall, valuable biochemical information was provided, a theoretical basis for a better understanding of psyllid-pathogen interactions was offered, and the findings may aid in breaking the transmission cycle of these diseases. [ABSTRACT FROM AUTHOR]

Candidatus Liberibacter solanacearum (CLso) is a complex of gram negative plant pathogenic and fastidious bacterial haplotypes restricted to the phloem and transmitted by several psyllid species. In Israel, the carrot psyllid Bactericera trigonica transmits CLso haplotype D in a persistent and propagative manner and causes the carrot yellows disease, inflicting significant economic losses in many countries. Understanding the transmission of CLso is fundamental to devising sustainable management strategies. Persistent transmission of vector‐borne pathogens involves the critical steps of adhesion, cell invasion and replication inside the insect gut cells before passage to the hemolymph. Using microscopy and expression analyses, we have previously confirmed a role for the endoplasmic reticulum (ER) in inducing immune responses and subsequent molecular pathways resulting in programmed cell death (apoptosis) upon CLso‐infection in the midgut. In the current study, we confirm that the ER‐associated degradation (ERAD) machinery and its associated marker genes were upregulated in CLso infected insects, including Derlin‐1, Selenoprotein‐1 and Ubiquitin Ligase RNF‐185. Silencing Derlin‐1, which acts on the ER membrane by regulating the degradation of unfolded proteins upon ER stress, revealed its role in CLso persistence and transmission. Molecular pathways initiated in the ER membrane upon bacterial infection are well documented in human, animal and insect systems, and this study confirms the role of the ER in CLso‐psyllid interactions. [ABSTRACT FROM AUTHOR]

ABSTRACT Autophagy plays an important role against pathogen infection in many organisms; however, little has been done with regard to vector-borne plant and animal pathogens, that sometimes replicate and cause deleterious effects in their vectors. Candidatus Liberibacter solanacearum (CLso) is a fastidious gram-negative phloem-restricted plant pathogen and vectored by the carrot psyllid, Bactericera trigonica. The plant disease caused by this bacterium is called carrot yellows and has recently gained much importance due to worldwide excessive economical losses. Here, we demonstrate that calcium ATPase, cytosolic calcium, and most importantly Beclin-1 have a role in regulating autophagy and its association with Liberibacter inside the psyllid. The presence of CLso generates reactive oxygen species and induces the expression of detoxification enzymes in the psyllid midguts, a main site for bacteria transmission. CLso also induces the expression of both sarco/endoplasmic reticulum Ca2+pump (SERCA) and 1,4,5-trisphosphate receptors (ITPR) in midguts, resulting in high levels of calcium in the cellular cytosol. Silencing these genes individually disrupted the calcium levels in the cytosol and resulted in direct effects on autophagy and subsequently on Liberibacter persistence and transmission. Inhibiting Beclin1-phosphorylation through different calcium-induced kinases altered the expression of autophagy and CLso titers and persistence. Based on our results obtained from the midgut, we suggest the existence of a direct correlation between cytosolic calcium levels, autophagy, and CLso persistence and transmission by the carrot psyllid. IMPORTANCE Plant diseases caused by vector-borne Liberibacter species are responsible for the most important economic losses in many agricultural sectors. Preventing these diseases relies mostly on chemical sprays against the insect vectors. Knowledge-based interference with the bacteria-vector interaction remains a promising approach as a sustainable solution. For unravelling how Liberibacter exploits molecular pathways in its insect vector for transmission, here, we show that the bacterium manipulates calcium levels on both sides of the endoplasmic reticulum membrane, resulting in manipulating autophagy. Silencing genes associated with these pathways disrupted the calcium levels in the cytosol and resulted in direct effects on autophagy and Liberibacter transmission. These results demonstrate major pathways that could be exploited for manipulating and controlling the disease transmission.

'Candidatus Liberibacter asiaticus’ (CLas) is associated with the devastating citrus disease Huanglongbing (HLB). Young flushes are the center of the HLB pathosystem due to their roles in the psyllid life cycle and in the acquisition and transmission of CLas. However, the early events of CLas infection and how CLas modulates young flush physiology remain poorly understood. Here, transmission electron microscopy analysis showed that the mean diameter of the sieve pores decreased in young leaves of HLB-positive trees after CLas infection, consistent with CLas-triggered callose deposition. RNA-seq-based global expression analysis of young leaves of HLB-positive sweet orange with (CLas-Pos) and without (CLas-Neg) detectable CLas demonstrated a significant impact on gene expression in young leaves, including on the expression of genes involved in host immunity, stress response, and plant hormone biosynthesis and signaling. CLas-Pos and CLas-Neg expression data displayed distinct patterns. The number of upregulated genes was higher than that of the downregulated genes in CLas-Pos for plant−pathogen interactions, glutathione metabolism, peroxisome, and calcium signaling, which are commonly associated with pathogen infections, compared with the healthy control. On the contrary, the number of upregulated genes was lower than that of the downregulated genes in CLas-Neg for genes involved in plant−pathogen interactions and peroxisome biogenesis/metabolism. Additionally, a time-course quantitative reverse transcription-PCR-based expression analysis visualized the induced expression of companion cell-specific genes, phloem protein 2 genes, and sucrose transport genes in young flushes triggered by CLas. This study advances our understanding of early events during CLas infection of citrus young flushes. [ABSTRACT FROM AUTHOR]

Simple Summary: The Asian citrus psyllid is the most widely distributed vector of the Asian form of huanglongbing, and the psyllid is a relatively minor pest in the absence of the pathogen. Pesticides used to suppress psyllid infestations can slow the rate of spread of the disease but not prevent it. Psyllid populations are known to be affected by a number of natural factors, including relative humidity, rainfall, ambient temperature, predators, parasitoids, and entomopathogens. However, in a recent study in Bhutan there was little evidence of these factors being responsible for the psyllid rarely occurring at elevations above 1200 m. It was hypothesised that ultraviolet radiation could be the cause. In this study, we observed how UV-A and UV-B affected the different stages of the psyllid. There was a negative impact of UV-A on all stages of psyllids, but UV-B was the more damaging. At the doses given, when adults were treated with UV radiation, there was little effect on the eggs or nymphs produced. Over the range of doses given, the Bunsen–Roscoe law of reciprocity held true for eggs and early instar nymphs. The result of our experiment suggests that ultraviolet light could be a factor affecting the distribution of D. citri populations. Populations of Diaphorina citri decline with elevation and, in a study in Bhutan, were rarely found above 1200 m ASL. The impact of ultraviolet (UV) radiation, particularly UV-B, on immature stages of the psyllid was proposed as limiting factor. As no studies have been undertaken on the influences of UV radiation on the development of D. citri, we examined the effects of UV-A and UV-B on different stadia of the psyllid. In addition, compliance with the Bunsen–Roscoe reciprocity law was examined. Irradiation with UV-A marginally reduced egg hatch and the survival times of emerging nymphs. Early instar nymphs were little affected by this waveband, but the survival of adults was reduced at the higher doses used. With UV-B, egg hatch and the survival times of early and late instar nymphs declined in proportion to UV-B dose. A dose of 57.6 kJ m−2 d−1 reduced the survival time of only adult females. Female fecundity was reduced at high UV-A and UV-B doses but increased at low doses. The Bunsen–Roscoe law held true for eggs and early instar nymphs for different durations and irradiances of UV-B. Eggs and nymphs had ED50 values for UV-B lower than the daily fluxes of this wavelength experienced worldwide. Thus, UV-B could be a factor causing the psyllid to be scarce at high elevations. [ABSTRACT FROM AUTHOR]

Psyllaephagus malloticolae Rawat & Kumar sp. nov. a parasitoid of Trioza malloticola (Crawford) (Hemiptera, Psylloidea, Triozidae) causing galls on leaves of the Kamala tree, Mallotus philippensis Muell, 1865 is described from India. An updated key to all the known allied species of Psyllaephagus Ashmead from India is also provided. The new species comes close to P. garuga Sudhir & Singh, 2011 but differs from it in having Funicular V the longest segment, mid-tibial spur longer than basitarsus, and the exserted ovipositor sheath. [ABSTRACT FROM AUTHOR]

'Candidatus Liberibacter solanacearum' (Lso) is a phloem-limited bacterial plant pathogen infecting solanaceous plants in the Americas and New Zealand and is associated with diseases of apiaceous crops in Europe, Northern Africa, and the Middle East. This pathogen is also related to other Liberibacter species that infect other crops. In the USA, two haplotypes of Lso, LsoA and LsoB, are predominant and responsible for diseases in potato and tomato. Tobacco, Nicotiana tabacum, a model species to study plant defenses, is a host for Lso; therefore, the interaction between Lso and this host plant could be used to study Liberibacter−plant interactions. In this study, we characterized the infection associated with LsoA and LsoB in tobacco. Under laboratory conditions, LsoB caused more severe symptoms than LsoA, and LsoA and LsoB titers were dynamic during the 7 weeks of the experiment. We also measured SA and other metabolites, including oxylipins, at an early point of infection and found that SA was accumulated in plants infected with LsoB but not with LsoA; whereas ABA levels were reduced in LsoA- but not in LsoB-infected plants. [ABSTRACT FROM AUTHOR]

Co-infection of plants by pathogens is common in nature, and the interaction of the pathogens can affect the infection outcome. There are diverse ways in which viruses and bacteria are transmitted from infected to healthy plants, but insects are common vectors. The present review aims to highlight key findings of studies evaluating the co-transmission of plant pathogens by insects and identify challenges encountered in these studies. In this review, we evaluated whether similar pathogens might compete during co-transmission; whether the changes in the pathogen titer in the host, in particular associated with the co-infection, could influence its transmission; and finally, we discussed the pros and cons of the different approaches used to study co-transmission. At the end of the review, we highlighted areas of study that need to be addressed. This review shows that despite the recent development of techniques and methods to study the interactions between pathogens and their insect vectors, there are still gaps in the knowledge of pathogen transmission. Additional laboratory and field studies using different pathosystems will help elucidate the role of host co-infection and pathogen co-transmission in the ecology and evolution of infectious diseases. [ABSTRACT FROM AUTHOR]

Abstract Background The tomato psyllid, Bactericera cockerelli Šulc (Hemiptera: Triozidae), is a pest of solanaceous crops such as tomato (Solanum lycopersicum L.) in the U.S. and vectors the disease-causing pathogen ‘Candidatus Liberibacter solanacearum’ (or Lso). Disease symptom severity is dependent on Lso haplotype: tomato plants infected with Lso haplotype B experience more severe symptoms and higher mortality compared to plants infected with Lso haplotype A. By characterizing the molecular differences in the tomato plant’s responses to Lso haplotypes, the key components of LsoB virulence can be identified and, thus, targeted for disease mitigation strategies. Results To characterize the tomato plant genes putatively involved in the differential immune responses to Lso haplotypes A and B, RNA was extracted from tomato ‘Moneymaker’ leaves 3 weeks after psyllid infestation. Gene expression levels were compared between uninfected tomato plants (i.e., controls and plants infested with Lso-free psyllids) and infected plants (i.e., plants infested with psyllids infected with either Lso haplotype A or Lso haplotype B). Furthermore, expression levels were compared between plants infected with Lso haplotype A and plants infected with Lso haplotype B. A whole transcriptome analysis identified 578 differentially expressed genes (DEGs) between uninfected and infected plants as well as 451 DEGs between LsoA- and LsoB-infected plants. These DEGs were primarily associated with plant defense against abiotic and biotic stressors, growth/development, plant primary metabolism, transport and signaling, and transcription/translation. These gene expression changes suggested that tomato plants traded off plant growth and homeostasis for improved defense against pathogens, especially when infected with LsoB. Consistent with these results, tomato plant growth experiments determined that LsoB-infected plants were significantly stunted and had impaired negative geotropism. However, it appeared that the defense responses mounted by tomatoes were insufficient for overcoming the disease symptoms and mortality caused by LsoB infection, while these defenses could compensate for LsoA infection. Conclusion The transcriptomic analysis and growth experiments demonstrated that Lso-infected tomato plants underwent gene expression changes related to abiotic and biotic stressors, impaired growth/development, impaired plant primary metabolism, impaired transport and signaling transduction, and impaired transcription/translation. Furthermore, the transcriptomic analysis also showed that LsoB-infected plants, relative to LsoA-infected, experienced more severe stunting, had improved responses to some stressors and impaired responses to others, had poorer transport and signaling transduction, and had impaired carbohydrate synthesis and photosynthesis.

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The relationship between herbivorous insects and plants is an example of an 'evolutionary arms race'. Understanding the relationship between insects and their host plants makes it possible to determine critical points in the bioecology of these herbivores. In this relationship, insects and plants use strategies to overcome, avoid and mitigate the actions of the other. Insect‐induced galls are one of the great examples of this 'arms race'. Psyllids (Hemiptera: Psylloidea) are among the most important gall‐inducing insects. The psyllid Triozoida limbata (Triozidae) is an important pest of guava (Psidium guajava) in the Neotropics. Thus, this work aimed to determine the morphological, anatomical, and biochemical changes in guava leaves caused by T. limbata to study the 'arms race' between these two organisms. Therefore, the process of gall formation on guava leaves during the psyllid life cycle was described. A comparative study of the anatomy and levels of phytohormones in leaves attacked and not attacked by the psyllid was carried out. It was found that the psyllid attack triggered the plant's defence by increasing the jasmonic acid content in the leaves. The psyllid attack caused anatomical changes in the leaves (such as cell non‐differentiation), allowing the insect to survive feeding on the plant. In addition, the psyllid‐induced galls provided shelter for the psyllid. [ABSTRACT FROM AUTHOR]

Background: The tomato psyllid, Bactericera cockerelli Šulc (Hemiptera: Triozidae), is a pest of solanaceous crops such as tomato (Solanum lycopersicum L.) in the U.S. and vectors the disease-causing pathogen 'Candidatus Liberibacter solanacearum' (or Lso). Disease symptom severity is dependent on Lso haplotype: tomato plants infected with Lso haplotype B experience more severe symptoms and higher mortality compared to plants infected with Lso haplotype A. By characterizing the molecular differences in the tomato plant's responses to Lso haplotypes, the key components of LsoB virulence can be identified and, thus, targeted for disease mitigation strategies. Results: To characterize the tomato plant genes putatively involved in the differential immune responses to Lso haplotypes A and B, RNA was extracted from tomato 'Moneymaker' leaves 3 weeks after psyllid infestation. Gene expression levels were compared between uninfected tomato plants (i.e., controls and plants infested with Lso-free psyllids) and infected plants (i.e., plants infested with psyllids infected with either Lso haplotype A or Lso haplotype B). Furthermore, expression levels were compared between plants infected with Lso haplotype A and plants infected with Lso haplotype B. A whole transcriptome analysis identified 578 differentially expressed genes (DEGs) between uninfected and infected plants as well as 451 DEGs between LsoA- and LsoB-infected plants. These DEGs were primarily associated with plant defense against abiotic and biotic stressors, growth/development, plant primary metabolism, transport and signaling, and transcription/translation. These gene expression changes suggested that tomato plants traded off plant growth and homeostasis for improved defense against pathogens, especially when infected with LsoB. Consistent with these results, tomato plant growth experiments determined that LsoB-infected plants were significantly stunted and had impaired negative geotropism. However, it appeared that the defense responses mounted by tomatoes were insufficient for overcoming the disease symptoms and mortality caused by LsoB infection, while these defenses could compensate for LsoA infection. Conclusion: The transcriptomic analysis and growth experiments demonstrated that Lso-infected tomato plants underwent gene expression changes related to abiotic and biotic stressors, impaired growth/development, impaired plant primary metabolism, impaired transport and signaling transduction, and impaired transcription/translation. Furthermore, the transcriptomic analysis also showed that LsoB-infected plants, relative to LsoA-infected, experienced more severe stunting, had improved responses to some stressors and impaired responses to others, had poorer transport and signaling transduction, and had impaired carbohydrate synthesis and photosynthesis. [ABSTRACT FROM AUTHOR]

Simple Summary: Zebra chip disease (ZC) in potato is an economically important disorder, documented in North and Central America and New Zealand. It is associated with the bacterium 'Candidatus Liberibacter solanacearum' (CaLsol), which is transmitted by the psyllid Bactericera cockerelli. The characteristic symptom of ZC is a dark and light striped pattern in chips, making them commercially unacceptable. Naturally CaLsol-infected potato tubers were reported in Europe, where the threat of ZC for European potato crops is a major concern. This work studied the presence and abundance of ZC symptoms and CaLsol in potato plants, as well as those psyllid species that eventually could transmit the bacterium, in the main producing areas in Spain. Very few symptomatic and CaLsol-positive plants were detected in Mainland Spain, and any positive plant was detected in the Canary Islands. Most of the adult psyllids captured were identified as Bactericera nigricornis, and some of them as Bactericera trigonica, but no B. cockerelli was detected. B. nigricornis was found widely distributed in the northern half of the Iberian Peninsula, and it was the only one able to feed and reproduce on potato plants. However, this psyllid does not seem sufficient to pose a threat to potato production, due to the scarce number of specimens and because the frequency of B. nigricornis specimens that were CaLsol+ was very low. 'Candidatus Liberibacter solanacearum' (CaLsol), the etiological agent of potato zebra chip (ZC), is transmitted to potato plants by the psyllid Bactericera cockerelli (Šulc, 1909) in North and Central America and New Zealand. The risk of the dispersion of ZC in Spain depends on the presence of an efficient vector. This work studies the presence and abundance of ZC symptoms and CaLsol in potato plants, as well as the presence and abundance of psyllid species associated with potato crops in the main producing areas in Spain. Eighty-eight plots were surveyed punctually to detect ZC symptoms and psyllid species in the main potato-producing areas. Furthermore, fourteen potato plots were surveyed by different sampling methods during the cropping season to detect psyllid species from 2016 to 2018. Very few symptomatic and CaLsol-positive plants were detected in Mainland Spain, and any positive plant was detected in the Canary Islands. Most of the adult psyllids captured were identified as Bactericera nigricornis (Foerster, 1848), and some of them as Bactericera trigonica, but no B. cockerelli was detected. B. nigricornis was found widely distributed in the northern half of the Iberian Peninsula; however, this psyllid does not seem sufficient to pose a threat to potato production, due to the scarce number of specimens and because the frequency of B. nigricornis specimens that were CaLsol+ was very low. [ABSTRACT FROM AUTHOR]

ABSTRACT Almost all known Liberibacters can be transmitted by psyllids. This suggests that there is a coevolutionary relationship between these two groups of organisms. However, detailed investigation of Liberibacters and psyllids have often focused on only a few species, thus potentially limiting knowledge on Liberibacter-psyllid associations. This study investigated the infection patterns of a Liberibacter inhabiting Macrohomotoma gladiata, a psyllid species feeding on Ficus microcarpa. Comparison of the Liberibacter’s near-full-length 16S rDNA sequence with those of other known Liberibacters revealed that it is closely related to Candidatus Liberibacter asiaticus. A survey of different M. gladiata populations in Taiwan using conventional and quantitative PCR (qPCR) indicated that the Liberibacter could be detected with variable frequencies in all the tested populations; the proportions of individuals carrying large Liberibacter populations also differed depending on the population. Additional analysis of a larger set of samples collected from one specific population revealed that the psyllid’s gender and abdominal color were associated with Liberibacter infection density. Significantly greater proportions of individuals with a blue/green abdomen carried high Liberibacter titers. Analysis of the psyllids’ body lengths revealed that body size was not affected by Liberibacter infection status and that females, particularly those with an orange abdomen, tended to be larger. The infection patterns of Liberibacter in nymph-infested and nymph-free twigs of F. microcarpa were also determined, and Liberibacter distribution was found to be associated with the presence of nymphs. These findings broaden the understanding of Liberibacter ecology in general and have implications for managing Liberibacter-associated diseases. IMPORTANCE Despite the ever-increasing interest in Liberibacter-psyllid interactions, most of the current knowledge on the subject has been established from studies focusing on species associated with crop diseases. To obtain a more holistic understanding of Liberibacter ecology, we investigated the infection patterns of a Liberibacter recently detected in Macrohomotoma gladiata, a psyllid pest of Ficus microcarpa. We showed that a Liberibacter closely related to Candidatus Liberibacter asiaticus is widely distributed across M. gladiata populations in Taiwan. The study also identified factors associated with the Liberibacter infection patterns, both in M. gladiata and in F. microcarpa. The effects of Liberibacter infection status on psyllid body sizes were also examined. Some of the patterns detected in this work were similar those found in well-known Liberibacters, while some were the opposite. The findings in this work broaden our understanding of Liberibacter ecology in general and may facilitate development of strategies for managing plant diseases.

On the basis of the sampling surveys in Biskra province during 2012 and 2019, fourteen distinct types of galls induced by insects were found on various host plants. They were belonging to three insect orders, four families and twelve genera. Most of the galls were induced by eight species of gall midges (Diptera: Cecidomyiidae), recently recorded from Biskra province, of which two species Houardiella salicornia Kieffer, 1912 and Gephyraulus moricandiae Sylven & Solinas, 1989 are first recorded from Algeria. The only known gall-inducing psyllid species Rhodochlanis salsolae (Lethierry, 1874) from Biskra (Algeria) as well as three gall-inducing aphid species associated with Pistacia atlantica were detected for the first time in Biskra province. These phytophagous species are associated with ten host plant species of which, the family Chenopodiaceae have the highest number of gall insects. Majority of the gallers are of Mediterranean origin, considered as economically indifferent species.

Cacopsylla pruni is a psyllid that has been known since 1998 as the vector of the bacterium ‘Candidatus Phytoplasma prunorum’, responsible for the European stone fruit yellows (ESFY), a disease that affects species of Prunus. This disease is one of the major limiting factors for the production of stone fruits, most notably apricot (Prunus armeniaca) and Japanese plum (P. salicina), in all EU stone fruit-growing areas. The psyllid vector is widespread in the Western Palearctic, and evidence for the presence of the phytoplasma that it transmits to species of Prunus has been found in 15 of the 27 EU countries.Recent studies showed that C. pruni is actually composed of two cryptic species, which can be differentiated by molecular markers. A literature review on the distribution of C. pruni was published in 2012, but it only provided presence or absence information at the country level and without distinction between the two cryptic species.Since 2012, numerous new records of the vector in several European countries have been published. We ourselves have acquired a large amount of data from sampling in France and other European countries. We have also carried out a thorough systematic literature review to find additional records, including all the original sources mentioning C. pruni (or its synonyms) since the first description by Scopoli in 1763. Our aim was to create an exhaustive georeferenced occurrence catalog, in particular in countries that are occasionnaly mentioned in the literature with little detail. Finally, for countries that seem suitable for the proliferation of C. pruni (USA, Canada, Japan, China, etc.), we digged deeper into the literature and reliable sources (e.g. checklist) to better subtanciate its current absence from those regions.Information on the distribution ranges of these vector psyllids is of crucial interest in order to best predict the vulnerability of stone fruit producing countries to the ESFY threat in the foreseeable future.We give free access to a unique file of 1975 records of all occurrence data in our possession concerning C. pruni, which we have gathered through more than twenty years of sampling efforts in Europe or through intensive text mining.We have made every effort to retrieve the source information for the records extracted from litterature (1201 records). Thus, we always give the title of the original reference, together with the page(s) citing C. pruni and, if possible, the year of sampling. To make the results of this survey publicly available, we give a URL to access the literature sources. In most cases, this link allows to freely download a PDF file.We also give access to information extracted from GBIF (162 exploitable data points on 245 occurrences found in the database), which we thoroughly checked and often supplemented to make the information more easily exploitable.We give access to our own unpublished georeferenced and genotyped record from 612 samples taken over the last 20 years in several European countries (Switzerland, Belgium, Netherlands, Spain, etc.). These include two countries (Portugal and North Macedonia) for which the presence of C. pruni had not been reported before. As our specimens have been genotyped (74 sites with species A solely, 202 with species B solely, and 310 with species A+B), our new data enable a better view of the geographical distribution of the two species at the Palaearctic scale.

Bell miner associated dieback (BMAD) is a prevalent type of eucalypt dieback along the eastern seaboard of Australia that is caused by repeated psyllid outbreaks, which are due to over-abundant bell miner birds excluding insectivorous birds. Despite strong evidence for this causal model, we have a limited understanding of how abiotic soil properties influence the interactions within the model. To address this knowledge gap, we compared the abiotic soil properties of Eucalyptus saligna forest stands affected and not affected by BMAD in New South Wales (NSW). We then tested whether the differences in the abiotic soil properties altered soil mycorrhizal fungal communities, bell miner bird nesting habitat availability via understorey thickening by Lantana camara (growth) and factors that may influence eucalypt-psyllid interactions including E. saligna feed quantity (tree size and leaf growth rate), feed quality (leaf nutrient content) and chemical defences (terpene emissions). We found that BMAD-affected stands had higher soil available phosphorus than stands not affected by BMAD, which was most likely due to topography. This higher soil available phosphorus was associated with greater L. camara growth and E. saligna leaf phosphorus content, suggesting it may be important in bell miner bird nesting habitat availability and the quality of feed available to psyllids. In contrast, the feed quantity and chemical defences of E. saligna were not related to soil available phosphorus. Our findings show that soil available phosphorus may play an important role in BMAD in eucalypt forests. Therefore, we can use remote sensing generated fine-scale soil nutrient maps to identify eucalypt stands that are vulnerable to BMAD and focus preventative management actions in these areas. • Bell miner associated dieback affected eucalypt forests have higher soil phosphorus. • Soil phosphorus causes understorey thickening, creating bell miner nesting habitat. • Soil phosphorus increases leaf phosphorus, improving feed quality to psyllids. [ABSTRACT FROM AUTHOR]

Trioza fletcheri Crawford is a sap-sucking psyllid that induces galls on Trewia nudiflora leaves. Early stages of T. fletcheri feed on parenchyma, whereas late-stages and adults feed on phloem, causing galls which arise in an isolated, agglomerated mass and rosette form only on the abaxial surface of T. nudiflora leaves. The feeding action of immature stages induces changes in metabolites of host tissue and creates a nutrition sink for feeding. The biochemical study revealed that galled tissues had higher levels of metabolites (total soluble sugars, reducing sugars, total protein and free amino acids) than ungalled tissues, with average values measuring 3.4±0.09, 1.4±0.1, 0.63±0.03, 1.9±0.23, 3.0±0.72mg/gdw in ungalled leaves; 4.3±0.02, 2.9±0.3, 1.9±0.47, 3.7±0.36, 4.7±0.53 mg/g dw in young galls; 3.8±0.50, 3.7±0.3, 1.03±0.04, 2.9±0.35, 5.4±0.31 mg/g dw in mature galls; and 2.7±0.23, 2.4±0.3, 0.83±0.03, 2.6±0.34 and, 4.3±0.22mg/g dw in old galls, respectively. Enhanced activities of IAA-oxidase, a-amylase, peroxidase, and invertase were observed in galled infested leaves than in ungalled leaves, and their values were measured to be 2.45±0.53, 2.4±0.3, 0.9±0.2, and 3.7±0.5 in ungalled leaves, 2.92±0.32, 3.2±0.2, 1.9±0.5 and 4.5±0.3in young galls, 3.7±0.43, 3.6±0.4, 1.4±0.4, 4.3±0.2 in mature galls, and 2.51±0.03, 2.9±0.4, 1.4±0.4, 3.8±0.1 in old galls respectively. [ABSTRACT FROM AUTHOR]

'Candidatus Liberibacter asiaticus' (CLas) is a bacterium that causes Huanglongbing, also known as citrus greening, in citrus plants. 'Candidatus Liberibacter solanacearum' (Lso) is a close relative of CLas and in the US it infects solanaceous crops, causing zebra chip disease in potato. Previously, we have identified the Lso hypothetical protein effector 1 (Lso-HPE1). This protein uses a signal peptide for secretion; disrupts programmed cell death; and interacts with tomato RAD23c, d, and e proteins, but not with RAD23a. In this study, we evaluated whether CLIBASIA_00460, the CLas homolog of Lso-HPE1 interacted with citrus RAD23 proteins and disrupted their programmed cell death. Based on the yeast two-hybrid assay results, CLIBASIA_00460 interacted with citrus RAD23c and RAD23d, but not with citrus RAD23b. These results were confirmed using bimolecular fluorescence complementation assays, which showed that these interactions occurred in cell puncta, but not in the nucleus or cytoplasm. Additionally, CLIBASIA_00460 was able to disrupt the PrfD1416V-induced hypersensitive response. Therefore, based on the similar interactions between Lso-HPE1 and CLIBASIA_00460 with the host RAD23 proteins and their ability to inhibit cell death in plants, we propose that these effectors may have similar functions during plant infection. [ABSTRACT FROM AUTHOR]

Simple Summary: The gall mite Aceria pallida can be phoretic on the psyllid Bactericera gobica to overwinter. Phoresy is often considered as a pattern of phoront–vector mutualism. The phoront A. pallida benefits from phoresy during the overwintering season, but no advantages to the vector B. gobica were found during this period. Therefore, this mutualism may occur during the growing season. Because both species share the same host plant and habitat after detachment, interspecific interactions are very likely to occur. To determine whether such interactions were positive or negative, we studied relationships between A. pallida and B. gobica egg abundances on leaves. Our study suggests positive interactions between two pests during the growing season. Outcomes of positive relationships between gall diameter and mite abundance in the gall provided a way to rapidly estimate mite abundances in the field by measuring gall diameters. The gall mite Aceria pallida and the psyllid Bactericera gobica are serious Goji berry pests. The mite can be phoretic on the psyllid to overwinter, but it is unclear whether the vector can obtain benefits from the phoront during the growing season. After detachment, the mite shares the same habitat with its vector, so there are very likely to be interspecific interactions. To better understand whether the interactions are positive or negative, information on relationships between abundances of A. pallida and B. gobica on leaves is needed. Here, B. gobica abundance was represented by the egg abundance because the inactive nymphs develop on the same sites after hatching. (1) We found a positive linear relationship between the gall diameter and the mite abundance in the gall (one more millimeter on gall diameter for every 30 mites increase), which provided a way to rapidly estimate mite abundances in the field by measuring gall diameters. (2) There was a positive relationship between the abundance of mites and psyllid eggs on leaves. (3) Both species had positive effects on each other's habitat selections. More importantly, the interactions of the two species prevented leaf abscission induced by B. gobica (leaf lifespan increased by 62.9%), increasing the continuation of the psyllid population. Our study suggests positive interactions between two pests during the growing season. The positive relationship between A. pallida and B. gobica egg abundances highlights the increasing need for novel methods for Goji berry pest management. In practice, A. pallida control can be efficient by eliminating its vector B. gobica. Both pests can be controlled together, which reduces chemical usage. [ABSTRACT FROM AUTHOR]

Eucalyptus spp. (Myrtaceae) is economically important worldwide and is native from Australia. Glycaspis brimblecombei (Hemiptera: Aphalaridae) is an insect that causes damages in eucalyptus plantations. Field observations show that highly infested plants (susceptible), less infested plants (less susceptible), and non-infested plants (resistant) can coexist at the same eucalyptus cultivation area. The aim of this study was to compare the preferences of Glycaspis brimblecombei with Eucalyptus spp. essential oil composition, evaluating the thermal behavior and searching for repellent compounds using chromatography. Simultaneous thermogravimetric and differential thermal analysis (TGA–DTA) results suggest that the less volatile essential oils were obtained from more resistant eucalyptus, with total mass loss temperature between 168 and 176 ºC. This behavior is due to the ratio between monoterpenes and sesquiterpenes in essential oils. Furthermore, D-limonene, caryophyllene, geranyl acetate, and other compounds may be correlated to the resistance against the insect. Gas chromatography–mass spectrometry (GC/MS) showed that susceptible samples had the highest concentrations of eucalyptol (77.0% and 49.8%) and lower concentration (3 and 9%) and variability of sesquiterpenes (7 and 10 compounds); additionally, they did not present β-guaiene, calamenene, α-copaene, α-terpinyl acetate, 1,4-cadinadiene, D-limonene, and caryophyllene in their essential oil composition. The eucalyptus resistance against Glycaspis brimblecombei is related to concentration and variability of sesquiterpenes, as well as the presence of specific compounds. [ABSTRACT FROM AUTHOR]

ABSTRACT Candidatus Liberibacter solanacearum (CLso) haplotype D, transmitted by the carrot psyllid Bactericera trigonica, is a major constraint for carrot production in Israel. Unveiling the molecular interactions between the psyllid vector and CLso can facilitate the development of nonchemical approaches for controlling the disease caused by CLso. Bacterial surface proteins are often known to be involved in adhesion and virulence; however, interactions of CLso with carrot psyllid proteins that have a role in the transmission process has remained unexplored. In this study, we used CLso outer membrane protein (OmpA) and flagellin as baits to screen for psyllid interacting proteins in a yeast two-hybrid system assay. We identified psyllid vitellogenin (Vg) to interact with both OmpA and flagellin of CLso. As Vg and autophagy are often tightly linked, we also studied the expression of autophagy-related genes to further elucidate this interaction. We used the juvenile hormone (JH-III) to induce the expression of Vg, thapsigargin for suppressing autophagy, and rapamycin for inducing autophagy. The results revealed that Vg negatively regulates autophagy. Induced Vg expression significantly suppressed autophagy-related gene expression and the levels of CLso significantly increased, resulting in a significant mortality of the insect. Although the specific role of Vg remains obscure, the findings presented here identify Vg as an important component in the insect immune responses against CLso and may help in understanding the initial molecular response in the vector against Liberibacter. IMPORTANCE Pathogen transmission by vectors involves multiple levels of interactions, and for the transmission of liberibacter species by psyllid vectors, much of these interactions are yet to be explored. Candidatus Liberibacter solanacearum (CLso) haplotype D inflicts severe economic losses to the carrot industry. Understanding the specific interactions at different stages of infection is hence fundamental and could lead to the development of better management strategies to disrupt the transmission of the bacteria to new host plants. Here, we show that two liberibacter membrane proteins interact with psyllid vitellogenin and also induce autophagy. Altering vitellogenin expression directly influences autophagy and CLso abundance in the psyllid vector. Although the exact mechanism underlying this interaction remains unclear, this study highlights the importance of immune responses in the transmission of this disease agent.

During the investigation of forest insects in Guilin, Guangxi, some encyrtids belonging to Psyllaephagus were reared from Macrohomotoma sinica (Hemiptera: Homotomidae) on Ficus concinna.A new species of Psyllaephagus Howard (Hymenoptera: Encyrtidae), P. guangxiensis Zu sp. nov., is described from Guangxi, China as a parasitoid of Macrohomotoma sinica Yang & Li (Hemiptera: Homotomidae) on Ficus concinna (Miq.) Miq. (Urticales: Moraceae).

Abstract Background The tomato psyllid, Bactericera cockerelli Šulc (Hemiptera: Triozidae), is a pest of solanaceous crops such as tomato (Solanum lycopersicum L.) in the U.S. and vectors the disease-causing pathogen ‘Candidatus Liberibacter solanacearum’. Currently, the only effective strategies for controlling the diseases associated with this pathogen involve regular pesticide applications to manage psyllid population density. However, such practices are unsustainable and will eventually lead to widespread pesticide resistance in psyllids. Therefore, new control strategies must be developed to increase host-plant resistance to insect vectors. For example, expression of constitutive and inducible plant defenses can be improved through selection. Currently, it is still unknown whether psyllid infestation has any lasting consequences on tomato plant defense or tomato plant gene expression in general. Results In order to characterize the genes putatively involved in tomato defense against psyllid infestation, RNA was extracted from psyllid-infested and uninfested tomato leaves (Moneymaker) 3 weeks post-infestation. Transcriptome analysis identified 362 differentially expressed genes. These differentially expressed genes were primarily associated with defense responses to abiotic/biotic stress, transcription/translation, cellular signaling/transport, and photosynthesis. These gene expression changes suggested that tomato plants underwent a reduction in plant growth/health in exchange for improved defense against stress that was observable 3 weeks after psyllid infestation. Consistent with these observations, tomato plant growth experiments determined that the plants were shorter 3 weeks after psyllid infestation. Furthermore, psyllid nymphs had lower survival rates on tomato plants that had been previously psyllid infested. Conclusion These results suggested that psyllid infestation has lasting consequences for tomato gene expression, defense, and growth.

Species of knotweeds, Reynoutria spp. Houtt. (Caryophyllales: Polygonaceae), including Japanese knotweed (R. japonica Houtt.), are among the most invasive and ecologically destructive plant species introduced to North America and Europe. The Kyushu strain of the psyllid Aphalara itadori Shinji (Hemiptera: Aphalaridae) has been approved as a biological control agent for release against Japanese knotweed in the United Kingdom, Canada, and the United States. However, recent reports from Canada suggest that both biotic and abiotic factors may limit its establishment. Therefore, we examined the potential role of predation by comparing open- versus closed-sleeve treatments, and climate mis-matches by collecting temperature data from release sites and performing climate suitability analyses using MaxEnt. Our results indicated that populations of the Kyushu strain could only be maintained in the field in closed-sleeve treatments, suggesting that predation is likely limiting the establishment success of this strain. In addition, we noted that daily maximum temperatures at our field sites might exceed documented developmental thresholds for this strain, and that MaxEnt species distribution modeling indicates no climate similarities between locations in eastern North America and Kyushu. Combined with previous results, our study suggests that the establishment of the Kyushu strain of A. itadori as a biological control agent for Japanese knotweed may be limited in eastern North America. We suggest that one strategy to increase the probability of establishment of the Kyushu strain could be to increase the number of release sites in an effort to find a more optimal niche with predator-free space. [ABSTRACT FROM AUTHOR]