Entomopathogenic nematodes in insect pest biocontrol: Diversity and function of excretory/secretory proteins.

Entomopathogenic nematodes (EPNs) are obligate parasitic "biopesticides" that play a vital role in pest management. A thorough understanding of their pathogenic mechanisms is essential for promoting their widespread use in agricultural pest control. The pathogenicity of EPNs arises from two key factors: the pathogenicity of their symbiotic bacteria and the nematodes' intrinsic pathogenic mechanisms. This review concentrates on the latter, offering an exploration of the excretory/secretory products of EPNs, along with their pathogenic mechanisms and key components. Particular attention is given to specific excretory/secretory proteins (ESPs) identified in various EPN species. The aim is to provide a foundational reference for comprehending the role of these ESPs in pest control. Furthermore, the review discusses the potential of these findings to advance the development of eco-friendly biopesticides, thereby supporting sustainable agricultural practices.

Root traits drive the recovery of soil nematodes during restoration of open mines in a tropical rainforest.

Mining is a major threat to vegetation and soil in the tropical forests. Reforestation of degraded surface mines is critically dependent on the recovery of soil health, where the nematodes play an important role. However, the key determinants of community assembly of soil nematodes during mine-restoration remain unknown in the tropical rainforests. Here, the recovery of taxonomic diversity of nematode communities and their trophic groups during reforestation of an extremely degraded tropical open-mining area is studied. The factors that may impact their recovery, such as root traits (length, area and tissue density), soil properties (pH and soil organic matter content (SOM)), and taxonomic diversities of soil bacterial and fungal communities are investigated. Differences in these parameters were evaluated in the three soil types: (i) mined soil - the erstwhile soil that was removed during mining and stock-piled for 10 years at the foot of an extremely degraded open-mining area; (ii) reforested soil, sampled from a 10-year successful restoration, which used the mined soil for reforestation; and (iii) undisturbed soil, collected from an adjacent undisturbed/not-mined tropical rainforest. A total of 11, 34 and 29 nematode-genera were identified in mined-, undisturbed-, and reforested soils, respectively. The taxonomic diversities of the 5 nematode groups in the mined soil were 1.5-5.2 times lower than in the undisturbed soil, but were similar in the restored and undisturbed soils. Taxonomic diversities of phytophagous and predator nematodes were correlated to restored root traits; whereas of bacterivores, fungivores, and omnivores were correlated to pH, SOM, soil bacterial and fungal communities. Consequently, complete loss of roots during mining likely severely reduced the nematodes, but their recovery after reforestation led to the restoration of taxonomic diversity of nematode communities. The mix-planting fast-growing tree species may be appropriate for recovering soil health, including nematode diversity, during reforestation of open tropical mines.

Genome sequences of Pseudomonas sp. strain FFPRI_1 and Photorhabdus temperata strain FFPRI_2, isolated from the entomopathogenic nematode, Heterorhabditis megidis.

The complete genome sequences of two bacteria isolated from an entomopathogenic nematode are reported. The genome sizes of Pseudomonas sp. strain FFPRI_1 and Photorhabdus temperata strain FFPRI_2 are 7,521,420 bp long with 63% G+C content and 5,483,510 bp long with 43.8% G+C content, respectively.

Plant-Parasitic Nematode Genera Associated with Date Palm in Central Iraq.

A survey of plant-parasitic nematode genera associated with roots of mature date palm trees was conducted in central Iraq to study the occurrence, population density and geographical distribution. This study in Baghdad, Babil, Diyala, Karbela, Najaf, and Wasit governorates was conducted from 2019 to 2023, during the months from October to April. A total of 150 soil and root samples were gathered from 46 fields, and plant parasitic nematodes were extracted and morphologically identified to genus level. Eleven genera of plant parasitic nematodes were detected in the declining order of frequency: Tylenchorhynchus spp. (20%) in Baghdad, Babil, Diyala, Karbala, and Najaf; Meloidogyne spp., (17.3%) in Baghdad, Babil, Diyala, Najaf, and Wasit; Paratylenchus spp. (16%) in Diyala and Najaf; Helicotylenchus spp. (12%) in Baghdad, Diyala, Najaf, and Wasit; Tylenchus spp. (12%) in Baghdad, Babil, Diyala, Najaf, and Wasit; Aphelenchoides spp. (6.7%) in Babil, Diyala, Karbala, and Wasit; Pratylenchus spp. (4%) in Baghdad, Diyala, Najaf, and Wasit; Ditylenchus spp. (3.3%) in Babil and Najaf; Hoplolaimus spp. (1.3%) in Diyala; and Heterodera spp. and Scutellonema spp. (0.7% each) in Diyala. Population density was low in Baghdad. High population density was recorded for Meloidogyne spp., (37625 J2 /1000 cm3 soil) and lowest population density occurred with Paratylenchus spp. (20 nematodes /1000 cm3 soil) in Diyala (Al-Jadidah). This appears to be the first report of occurrences of plant-parasitic nematodes of date palm in central Iraq.

Modeling the distribution of pine wilt disease in China using the ensemble models MaxEnt and CLIMEX.

Pine wilt disease (PWD) is a devastating plant disease caused by the pinewood nematode (PWN, Bursaphelenchus xylophilus) that is transmitted by several beetle species in the genus, Monochamus. Once present, the disease is difficult to control. Prevention rather than control is regarded as an effective strategy for PWD management. Central to this prevention strategy is the ability to predict the potential distribution of the disease. Here, we employed an integrated MaxEnt and CLIMEX approach to model the potential distribution of PWD under various climate-change scenarios. Our results indicate that rising temperatures and lower humidity under climate change will render some of the northern regions of China more suitable for the nematode and these beetles, causing the gradual northward movement of PWD. Furthermore, suitable habitats for three pine species, Pinus massoniana, P. taiwanensis and P. shurbergia, overlap with PWN and Monochamus, suggesting that these three species are potentially at high risk of PWD. Thus, PWD management should target the northern regions of China and the three pine species that are most susceptible to PWD.

Capillaria hepatica (syn. Calodium hepaticum) infection and factors influencing infection carriage in rats (Rattus spp.) in Hong Kong.

Capillaria hepatica (syn. Calodium hepaticum) (Bancroft, 1893) is a nematode, which colonises the liver of a wide range of hosts including humans. The worldwide prevalence of infection in the genus Rattus can be as high as 100% and the Norway rat (R. norvegicus) and black rat (R. rattus) are considered the main host species. This study is the first to investigate the epidemiology of C. hepatica infection in wild rats trapped in various geographical locations in Hong Kong. Four species of trapped rats were identified, with 65% being R. norvegicus, followed by 30% R. tanezumi (Asian house rat), 4% R. andamanensis (Sikkim rat), and 1% Niviventer huang (South China white-bellied rat). The overall prevalence of C. hepatica infection was 36.7% (81/221) (95% CI 30.4-43.4) and R. norvegicus was the most common rat species trapped during this study, with the highest prevalence of C. hepatica infection. Two risk factors for host infection were skin wounds and geographical region, whilst sex, body weight, stage of development, and presence of ectoparasites were not risk factors for this infection. Gross hepatic lesions were absent in 17% of infected rats and when present, were not pathognomonic for the infection. Infected rats lacked severe hepatic inflammation or fibrosis, indicating that rats tolerate the infection well. Egg production was observed in the livers of 69% of infected rats, which emphasizes their role as reservoirs of this zoonotic parasite. Several infected rats in this study were trapped inside residential buildings, which highlights the zoonotic risk of C. hepatica to humans following the potential ingestion of embryonated eggs from contaminated food, water, or soil.

Molinostrongylus longmenensis n. sp. (Strongylida: Molineidae) in the bat Scotophilus kuhlii (Leach; Chiroptera: Vespertilionidae) from China.

A new species of nematode, Molinostrongylus longmenensis n.sp., parasite of the genus Molinostrongylus, is described based on specimens recovered from the small intestine of Scotophilus kuhlii Leach, 1822 (Chiroptera: Vespertilionidae) in Longmen County, Guangdong Province, China. To date, 135 species of bat-parasitic nematodes have been reported worldwide. Overall, 13 species belonging to seven genera in three families have been described in China. The new species is characterized by the presence of three ventral and three dorsal longitudinal cuticular ridges perpendicular to the body surface, which appear posterior to the cephalic vesicle and extend to the caudal bursa in males and the posterior end in females. The female tail has two medium-sized subventral conical processes of equal length, as well as one large dorsal conical process, and one thin spine, lateral alae that extend to the position of the vulva, with a fin-like ending. In addition, the new species was also characterized using molecular approaches, such as sequencing and analyzing the internal transcribed spacer 1 (ITS-1) of the ribosomal DNA.

Reduced anthelmintic use on 13 New Zealand sheep farms: farmer motivations and practical implementation.

AIMS: To describe the personal drivers, sources of information and gastro-intestinal parasite control methods used by a group of New Zealand sheep farmers identified as low users of anthelmintic (AHC), and their perception of the efficacy and impacts of this approach. METHODS: A convenience sample of 13 sheep farmers farming with a policy of reduced AHC use (no pre-determined routine treatments of ewes >19 months old and/or lambs not routinely treated at pre-determined intervals from weaning through to late autumn) were identified. Semi-structured interviews were conducted regarding their farming philosophy, motivations for reducing AHC use, perceptions of the impacts of farming with reduced AHC use, and parasite control practices. Semi-quantitative data were analysed using descriptive statistics for demographic data and categorising participants' use of AHC and non-chemical control methods. Qualitative data regarding participants' motivations, approaches and rationale were analysed by systematic analysis of the transcripts and distillation of key concepts. RESULTS: Participants had been operating with reduced AHC use for 3 to ≥20 years. Key motivators for reducing AHC use were a diagnosis of anthelmintic resistance (AR) or concerns about AR developing. Parasite management information came from a wide range of sources. All respondents expressed overall positive views regarding the impacts of reduced AHC use but detailed information was not available.All identified that regular monitoring, based primarily on subjective animal and non-animal factors was important for their parasite control strategy. Most used faecal egg counts (FEC), often in an ad hoc manner. Five never treated adult ewes, two routinely treated ewes prior to lambing with short-acting AHC and the remainder occasionally treated a small number in low body condition. Four routinely treated some or all lambs at 28-30-day intervals from weaning to late autumn while the remainder based their treatment decisions for lambs on monitored information. All placed heavy emphasis on feeding sheep well, ensuring high post-grazing residuals, and cross-grazing. CONCLUSIONS: AR was a key motivator for participants to reduce AHC use, and a range of information sources and decision-making processes were used. Key parasite management practices were monitoring, primarily using subjective assessments, emphasis on feeding stock well and cross-grazing. CLINICAL RELEVANCE: The rising prevalence of AR will likely result in increasing the motivation for sheep farmers to reduce their AHC use. Veterinarians will play a key role in providing advice and assistance to facilitate changes in parasite management.

Human Infection with the Nematode Gongylonema sp.: A Case Report from Bulgaria.

We report a case of infection with the zoonotic nematode Gongylonema sp. in a 24-year-old woman from Varna, Bulgaria. Two days before seeking medical attention, the patient had noticed a filamentous mass in her buccal mucosa that migrated when touched with the tongue. She manually removed a thread-like worm from the mucosa near her lower lip. Albendazole was prescribed for three days. The patient had no history of travelling abroad or contact with animals. To our knowledge, this is the sixth case that has been reported in the country.

Real-time qPCR coupled with high-resolution melting curve analysis for the detection of the internal transcribed spacer 1 of Angiostrongylus costaricensis.

Abdominal angiostrongyliasis (AA) is a zoonotic and severe parasitic infection caused by Angiostrongylus costaricensis. AA is currently diagnosed by the observation of A. costaricensis-compatible structures in biopsies or the detection of antibodies in serological tests. However, molecular methods targeting homologous sequences of A. costaricensis have not been designed before, and therefore, an HRM-coupled qPCR was developed to detect the internal transcribed spacer 1 (ITS1) of the parasite. The present assay successfully amplified DNA of A. costaricensis obtained from different hosts and identified slight sequence differences through the HRM analysis. The detection limit of the HRM-qPCR was 0.00036 ng/µL, 1.0 ng/µL, and 0.1 ng/µL when A. costaricensis DNA was diluted in nuclease-free water, whole blood, and sera, respectively, which highlights its potential use for cell-free DNA detection. Moreover, the reaction did not cross-amplify DNA of Angiostrongylus cantonensis, Strongyloides stercoralis, and other nematodes, thus emphasizing its specificity. Additionally, the assay tested positive in formalin-fixed paraffin embedded biopsies with visible A. costaricensis adults or eggs, but not in samples without evident parasites or a low number of larvae, which suggests that the reaction is useful for confirming the presence of the nematode in clinical samples. Finally, DNA of sera from patients with AA was evaluated with the HRM-qPCR but none tested positive, possibly due to long storage periods of the samples which could have led to cfDNA degradation. These results indicate that this assay may be useful in the confirmation of AA and its prospection for cell-free DNA detection protocols.

Entomopathogenic nematode detection and counting model developed based on A-star algorithm.

Entomopathogenic nematodes are soil-dwelling living organisms widely employed in the biological control of agricultural insect pests, serving as a significant alternative to pesticides. In laboratory procedures, the counting process remains the most common, labor-intensive, time-consuming, and approximate aspect of studies related to entomopathogenic nematodes. In this context, a novel method has been proposed for the detection and quantification of Steinernema feltiae isolate using computer vision on microscope images. The proposed method involves two primary algorithmic steps: framing and isolation. Compared to YOLO-V5m, YOLO-V7m, and YOLO-V8m, the A-star-based developed network demonstrates significantly improved detection accuracy compared to other networks. The novel method is particularly effective in facilitating the detection of overlapping nematodes. The developed algorithm excludes processes that increase space and time complexity, such as the weight document, which contains the learned parameters of the deep learning model, model integration, and prediction time, resulting in more efficient operation. The results indicate the feasibility of the proposed method for detecting and counting entomopathogenic nematodes.

Gastrointestinal nematodes in German outdoor-reared pigs based on faecal egg count and next-generation sequencing nemabiome data.

BACKGROUND: There is a higher risk for nematode infections associated with outdoor-reared pigs. Next to Ascaris suum, Oesophagostomum dentatum and Trichuris suis, there is the potential of infections with other nodular worm species, Hyostrongylus rubidus, Stongyloides ransomi and Metastrongylus spp. lungworms. Next-generation sequencing methods describing the nemabiome have not yet been established for porcine nematodes. METHODS: FLOTAC was used for faecal egg counts of porcine gastrointestinal nematodes and lungworms in piglets, fatteners and adults individually. A nemabiome analyses based on ITS-2 gene region metabarcoding was used to differentiate strongyle species. Additionally, questionnaire data was analysed using mixed-effect regression to identify potential risk factors associated with parasite occurrences and egg shedding intensity. RESULTS: On 15 of 17 farms nematode eggs were detected. Ascaris suum, strongyles and T. suis were detected on 82%, 70% and 35% of the 17 farms, respectively. Lungworms were detected on one out of four farms with access to pasture. Strongyloides ransomi was not detected. 32% (CI 28-36%), 27% (24-31%), 5% (4-7%) and 3% (0.9-8%) of the samples where tested positive for strongyles, A. suum, T. suis and lungworms, respectively. The nemabiome analysis revealed three different strongyle species, with O. dentatum being the most common (mean 93.9%), followed by O. quadrispinulatum (5.9%) and the hookworm Globocephalus urosubulatus (0.1%). The bivariate and multivariate risk factor analyses showed among others that cleaning once a week compared to twice a week increased the odds significantly for being infected with A. suum (OR 78.60) and strongyles (2077.59). Access to pasture was associated with higher odds for A. suum (43.83) and strongyles (14.21). Compared to shallow litter systems, deep litter and free range systems resulted in significant higher odds for strongyles (85.74, 215.59, respectively) and T. suis (200.33, 623.08). CONCLUSIONS: Infections with A. suum, O. dentatum, O. quadrispinulatum, T. suis, Metastrongylus spp. and G. urosubulatus are present in German outdoor-reared pigs. This is the first report of G. urosubulatus in domestic pigs in Europe. Metabarcoding based on the ITS-2 region is a suitable tool to analyse the porcine nemabiome. Furthermore, management practices have the potential of reducing the risk of parasite infections.

First Report and Molecular Variability of Belonolaimus longicaudatus Associated with Turfgrass in Maryland.

Turfgrass is a crop used extensively in athletic fields and golf courses in Maryland. A soil sample collected in July 2023 from an athletic field in Baltimore County, Maryland, part of a turfgrass nematode survey, contained Belonolaimus longicaudatus. In the southeastern United States, B. longicaudatus is an economically important pathogen of warm season turfgrass. The density was four individuals/100 cm3 of soil, and no visual symptoms were observed in the bermudagrass field. Morphological features and morphometrics of males and females were consistent with B. longicaudatus and placed the Maryland population in a subclade that was geographically represented by populations from north and west Florida, Texas, and South Carolina. Sequencing of the internal transcribed spacer region ITS1 and ITS2 and 28S large ribosomal subunit D2-23 expansion region confirmed the species' identity. Phylogenetic trees and parsimony network analysis placed the Maryland isolate in a large grouping of B. longicaudatus populations including those from Alabama, Delaware, Florida, Indiana, Mississippi, South Carolina, and Texas. To our knowledge, this is the first report of B. longicaudatus in Maryland.

Symbiotic and Nonsymbiotic Bacteria Associated With the Entomo-Pathogenic Nematode, Heterorhabditis spp (Rhabditida: Heterorhabditidae) From South India.

Sixteen isolates of bacteria obtained from the entomopathogenic nematode (Heterorhabditis sp.) infected cadavers of Galleria mellonella larvae were identified following phenotypic characterization and molecular analysis of 16S rRNA. Two isolates were identified as the symbiotic bacterium, Photothabdus luminescens, while 14 other isolates were represented by nine species of nonsymbiotic bacteria viz., Stenotrophomonas maltophilia, Alcaligenes aquatilis, Brevundimonas diminuta, Brucella pseudointermedia, Ochrobactrum sp., Brucella pseudogrignonensis, Brucella anthropic, Pseudomonas azatoformans and Pseudomonas lactis. The phylogenetic analysis confirmed the evolutionary relationship between P. luminescens and Pseudomonas spp. The study also found a close relationship among the nonsymbiotic bacteria such as A. aquatilis, B. diminuta, Ochrobactrum sp., and Brucella spp. P. luminescens has been documented for its insecticidal effects against a wide range of insects. The two local isolates obtained in this study may be explored for their biocontrol potential against major pests of the region. Further, the association of nonsymbiotic bacteria with the EPN may be investigated.

Neurotoxicity induced by aged microplastics from plastic bowls: Abnormal neurotransmission in Caenorhabditis elegans.

The use of plastic bowls (PB) has garnered increasing scrutiny due to the inevitable generation of microplastics (MPs) throughout their lifecycle. Despite this concern, there exists a limited understanding of the behaviors, toxicological effects, and mechanisms associated with aged PB (A-PB). This research investigated the photoaging properties of A-PB following ultraviolet irradiation and evaluated the neurotoxic impact of exposure to A-PB at environmentally relevant concentrations (0.001-1 mg/L) on Caenorhabditis elegans. Significant alterations in the crystallinity, elemental composition, and functional groups of A-PB were observed compared to virgin PB (V-PB), along with the emergence of environmentally persistent free radicals and reactive oxygen species. Toxicity assessments revealed that exposure to 0.1-1 mg/L A-PB induced greater neurotoxicity on locomotion behaviors compared to V-PB, as evidenced by marked reductions in head thrashes, body bends, wavelength, and mean amplitude. Exposure to A-PB also altered the fluorescence intensities and neurodegeneration percentage of dopaminergic, serotonergic, and GABAergic neurons, suggesting neuronal damage in the nematodes. Correspondingly, decreases in the levels of dopamine, serotonin, and GABA were noted together with significant drops in the expression of neurotransmitter-related genes (e.g., dat-1, tph-1, and unc-47). Correlation analyses established a significant positive relationship between these genes and locomotion behaviors. Further exploration showed the absence of locomotion behaviors in dat-1 (ok157), tph-1 (mg280), and unc-47 (e307) mutants, underscoring the pivotal roles of the dat-1, tph-1, and unc-47 genes in mediating neurotoxicity in C. elegans. This study sheds light on the photoaging characteristics and heightened toxicity of A-PB, elucidating the mechanisms driving A-PB-induced neurotoxicity.

Streptomyces avermitilis MICNEMA2022: a new biorational strain for producing abamectin as an integrated nematode management agent.

BACKGROUND: Abamectin (ABA) is considered a powerful insecticidal and anthelmintic agent. It is an intracellular product of Streptomyces avermitilis; is synthesized through complicated pathways and can then be extracted from mycelial by methanol extraction. ABA serves as a biological control substance against the root-knot nematode Meloidogyne incognita. This investigation is intended to reach a new strain of S. avermitilis capable of producing ABA effectively. RESULTS: Among the sixty actinobacterial isolates, Streptomyces St.53 isolate was chosen for its superior nematicidal effectiveness. The mycelial-methanol extract of isolate St.53 exhibited a maximum in vitro mortality of 100% in one day. In the greenhouse experiment, the mycelial-methanol extract demonstrated, for the second-stage juveniles (J2s), 75.69% nematode reduction and 0.84 reproduction rate (Rr) while for the second-stage juveniles (J2s), the culture suspension demonstrated 75.38% nematode reduction and 0.80 reproduction rate (Rr). Molecular identification for St.53 was performed using 16 S rRNA gene analysis and recorded in NCBI Genbank as S. avermitilis MICNEMA2022 with accession number (OP108264.1). LC-MS was utilized to detect and identify abamectin in extracts while HPLC analysis was carried out for quantitative determination. Both abamectin B1a and abamectin B1b were produced and detected at retention times of 4.572 and 3.890 min respectively. CONCLUSION: Streptomyces avermitilis MICNEMA2022 proved to be an effective source for producing abamectin as a biorational agent for integrated nematode management.

Comparative histopathology of virulent and avirulent Meloidogyne javanica populations on susceptible and resistant tomato plants.

The Mi-1.2 gene confers resistance to a wide range of Meloidogyne species, being the most important resistance factor employed in tomato breeding so far. However, many aspects related to the interaction of Mi-1.2-carrying tomato cultivars and virulent/avirulent Meloidogyne populations have not yet been clarified. Herein, comparative histopathological analyses were carried after inoculation of the homozygous (Mi-1.2/Mi-1.2) tomato rootstock 'Guardião' and the susceptible cultivar 'Santa Clara' (mi-1.2/mi-1.2) with virulent and avirulent populations of M. javanica. In the susceptible control, it was possible to visualize second stage juveniles (J2) of avirulent population and feeding sites from 2 to 30 days after infection (DAI) with females reaching maturity at 24-34 DAI. In the resistant rootstock, the Mi-1.2 gene-mediated resistance was related mainly to early defense responses (pre-infection and hypersensitive reaction), which led to an immunity-like phenotype that completely prevented the reproduction of the avirulent Meloidogyne population. On the other hand, J2s of the virulent M. javanica population were able to penetrate roots much more than the avirulent population, migrated and developed normally, showing intense and similar pattern of penetration from 4 to 34 DAI in the root tissues of both resistant and susceptible tomato genotypes. The total numbers of J2, J3, J4, and females counted in 'Santa Clara' for the virulent population of M. javanica were higher than in 'Guardião'.

Integration of soil microbiology and metabolomics to elucidate the mechanism of the accelerated infestation of tobacco by the root-knot nematode.

Introduction: Tobacco root-knot nematode (TRKN) disease is a soil-borne disease that presents a major hazard to the cultivation of tobacco, causing significant reduction in crop quality and yield, and affecting soil microbial diversity and metabolites. However, differences in rhizosphere soil microbial communities and metabolites between healthy tobacco soils and tobacco soils with varying degrees of TRKN infection remain unclear. Methods: In this study, diseased rhizosphere soils of tobacco infected with different degrees of TRKN [severally diseased (DH) soils, moderately diseased (DM) soils, and mildly diseased (DL) soils] and healthy (H) rhizosphere soils were collected. Here, we combined microbiology with metabolomics to investigate changes in rhizosphere microbial communities and metabolism in healthy and TRKN-infected tobacco using high-throughput sequencing and LC-MS/MS platforms. Results: The results showed that the Chao1 and Shannon indices of bacterial communities in moderately and mildly diseased soils were significantly higher than healthy soils. The Proteobacteria, Actinobacteria, Ascomycota, Burkholderia, Bradyrhizobium and Dyella were enriched in the rhizosphere soil of healthy tobacco. Basidiomycota, Agaricales, Pseudeurotiaceae and Ralstonia were enriched in severally diseased soils. Besides, healthy soils exhibited a relatively complex and interconnected network of bacterial molecular ecologies, while in severally and moderately diseased soils the fungal molecular networks are relatively complex. Redundancy analysis showed that total nitrogen, nitrate nitrogen, available phosphorus, significantly affected the changes in microbial communities. In addition, metabolomics results indicated that rhizosphere soil metabolites were significantly altered after tobacco plants were infected with TRKNs. The relative abundance of organic acids was higher in severally diseased soils. Spearman's analyses showed that oleic acid, C16 sphinganine, 16-hydroxyhexadecanoic acid, D-erythro-3-methylmalate were positively correlated with Basidiomycota, Agaricales, Ralstonia. Discussion: In conclusion, this study revealed the relationship between different levels of TRKN invasion of tobacco root systems with bacteria, fungi, metabolites and soil environmental factors, and provides a theoretical basis for the biological control of TRKN disease.

A New Cyst Nematode, Heterodera luodingensis n. sp. (Nematoda: Heteroderinae) From Rice In China.

A unique cyst nematode population (Heterodera spp.) was collected from rice roots in Luoding County, Guangdong Province, China. Morphological and molecular analyses revealed it is significantly different from all previously described cyst nematode species. It is described as Heterodera luodingensis n. sp. and classified in the Cyperi group. H. luodingensis n. sp. is characterized by its lemon-shaped cyst with a prominent terminal vulval cone that is ambifenestrate with abundant bullae and a relatively short vulval slit, 31.3 (24.4 -38.7) µm long. The second-stage juveniles (J2) are characterized by dumbbell shaped labials, three lip annules and a lateral field with three incisures. The J2 stylet is 18.7 (16.9 -19.8) µm long with anterior concave or spherical knobs. The tail is elongate conoid, tapering to a rounded terminus or zig tapering to a rounded terminus that is 54.9 (43.9 - 64.3) µm long with a hyaline region comprising 40.3%-52.5% of the tail. Phylogenetic tree analysis based on rDNA 28S D2D3 and ITS fragments showed that the H. luodingensis n. sp. is unique and clearly separated it from other cyst nematodes. It is most closely related to H. oryzicola, H. fengi, H. elachista, H. oryzae, and H. guangdongensis. H. luodingensis n. sp. can be distinguished from H. oryzicola by its shorter vulval slit and underbridge, from H. elachista by abundant bullae, shorter vulval slit and fenestrate width, from H. oryzae by a shorter vulval slit and underbridge, from H. fengi by a shorter vulval slit, from H. guangdongensis by a longer cyst length and abundant bulla. Based on PCR-RFLP of rDNA-ITS, H. luodingensis n. sp. can be clearly distinguished from H. oryzicola, H. mothi, H. elachista, H. guangdongensis and H. cyperi. A parasitism test from a pure culture derived from a single cyst in greenhouse showed that H. luodingensis n. sp. can successfully complete its life cycle on rice and rice is its type host.

Pinewood nematode induced changes in the assembly process of gallery microbiomes benefit its vector beetle's development.

Microbiomes play crucial roles in insect adaptation, especially under stress such as pathogen invasion. Yet, how beneficial microbiomes assemble remains unclear. The wood-boring beetle Monochamus alternatus, a major pest and vector of the pine wilt disease (PWD) nematode, offers a unique model. We conducted controlled experiments using amplicon sequencing (16S rRNA and ITS) within galleries where beetles and microbes interact. PWD significantly altered bacterial and fungal communities, suggesting distinct assembly processes. Deterministic factors like priority effects, host selection, and microbial interactions shaped microbiome composition, distinguishing healthy from PWN-infected galleries. Actinobacteria, Firmicutes, and Ophiostomataceae emerged as potentially beneficial, aiding beetle's development and pathogen resistance. This study unveils how nematode-induced changes in gallery microbiomes influence beetle's development, shedding light on microbiome assembly amid insect-pathogen interactions. Insights gleaned enhance understanding of PWD spread and suggest novel management strategies via microbiome manipulation.IMPORTANCEThis study explores the assembly process of gallery microbiomes associated with a wood-boring beetles, Monochamus alternatus, a vector of the pine wilt disease (PWD). By conducting controlled comparison experiments and employing amplicon approaches, the study reveals significant changes in taxonomic composition and functional adaptation of bacterial and fungal communities induced by PWD. It identifies deterministic processes, including priority effects, host selection, and microbial interactions, as major drivers in microbiome assembly. Additionally, the study highlights the presence of potentially beneficial microbes such as Actinobacteria, Firmicutes, and Ophiostomataceae, which could enhance beetle development and resistance to pathogens. These findings shed light on the intricate interplay among insects, microbiomes, and pathogens, contributing to a deeper understanding of PWD prevalence and suggesting innovative management strategies through microbiome manipulation.