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Pine Wilt Disease (PWD) is a devastating pine tree disease characterized by rapid onset, high mortality rate, quick spread, and difficulty in control. Plant microbiome plays a significant role in the development of PWD. However, the endophytic microbial communities of Pinus koraiensis infected by pine wood nematode (PWN) Bursaphelenchus xylophilus remain largely unexplored. In this study, we analyzed the structural changes of endophytic communities of P. koraiensis after infection by the PWN using high-throughput sequencing technology. The results showed that the community structure underwent significant changes as the degree of PWN infection intensified. The diversity and abundance of endophytic fungi in P. koraiensis increased, while those of endophytic bacteria in P. koraiensis decreased during the infection process. Meanwhile, the abundance of some dominant microorganisms has also changed, including species such as Graphilbum and Pseudoalteromonas. Functional prediction analysis showed that the functional composition of endophytic fungi in P. koraiensis was significantly different across the development of PWD, while the composition of endophytic bacteria remained essentially similar. The results indicated that PWN infection had a significant impact on the structure, diversity, abundance, and functional gene composition of endophytic microbial communities in P. koraiensis , and most of the main endophytic microbial groups tended to coordinate with each other. This work provides a better understanding of the changes in endophytic community structure and function caused by PWD infection of P. koraiensis , which may benefit the exploration of potential endophytes for PWN biocontrol. [ABSTRACT FROM AUTHOR]

Plant resistance (R) genes play a crucial role in the detection of effector proteins secreted by pathogens, either directly or indirectly, as well as in the subsequent activation of downstream defence mechanisms. However, little is known about how R genes regulate the defence responses of conifers, particularly Pinus massoniana, against the destructive pine wood nematode (PWN; Bursaphelenchus xylophilus). Here, we isolated and characterised PmHs1pro‐1, a nematode‐resistance gene of P. massoniana, using bioinformatics, molecular biology, histochemistry and transgenesis. Tissue‐specific expressional pattern and localisation of PmHs1pro‐1 suggested that it was a crucial positive regulator in response to PWN attack in resistant P. massoniana. Meanwhile, overexpression of PmHs1pro‐1 was found to activate reactive oxygen species (ROS) metabolism‐related enzymes and the expressional level of their key genes, including superoxide dismutase, peroxidase and catalase. In addition, we showed that PmHs1pro‐1 directly recognised the effector protein BxSCD1of PWN, and induced the ROS burst responding to PWN invasion in resistant P. massoniana. Our findings illustrated the molecular framework of R genes directly recognising the effector protein of pathology in pine, which offered a novel insight into the plant–pathogen arms race. Summary statement: We first identified and functionally characterised that PmHs1pro‐1 could directly recognise the effector protein BxSCD1, which consequently initiated the ROS burst to defend against pine wood nematode to prevent the withered appearance in the resistant Pinus massoniana. Our findings demonstrated the molecular framework of R genes directly recognising the effector protein of pathology in pines and offered a novel insight into the plant‐arm race of pathogens and plants. [ABSTRACT FROM AUTHOR]

Simple Summary: Longhorn beetles of the genus Monochamus are vectors of the pine wood nematode, which causes incurable pine wilt disease in coniferous trees. We developed temperature-dependent models to describe the oviposition of Monochamus saltuarius, a significant species within this genus. Our study demonstrated that these models effectively capture the nonlinear effects of temperature on the oviposition and aging of M. saltuarius adults. We compared two simulation approaches: one that separately accounted for the sexual maturation phase of adults and another that did not. Both methods proved capable of accurately describing oviposition patterns across various temperature conditions. The insights gained from this study have potential applications beyond estimating oviposition and predicting population dynamics of M. saltuarius. This modeling framework could be adapted to forecast population changes in a diverse range of pest species, offering a versatile tool for pest management strategies. Monochamus saltuarius Gebler is a serious insect pest in Europe and East Asia regions, including Portugal, Spain, China, Japan, and Korea. It transfers the pine wood nematode Bursaphelenchus xylophilus to conifer trees, resulting in pine wilt disease (PWD). As temperature is a key factor influencing insect population dynamics, temperature-dependent models describing M. saltuarius oviposition could estimate population growth potential and evaluate outbreak risks. In this study, the longevity and fecundity of M. saltuarius females were measured under constant temperature conditions ranging from 20 to 32 °C, and temperature-dependent models were constructed. The longevity of M. saltuarius females ranged from 83.36 days to 22.92 days, with a total fecundity of 141 eggs and 52.77 eggs at 20 °C and 32 °C, respectively. To describe oviposition, we used a single-phase simulation describing oviposition as a single model and a two-phase simulation describing sexual maturation and oviposition as two separate models. These models effectively described M. saltuarius oviposition (r2 > 0.96) under constant temperature conditions, with the two-phase simulation demonstrating greater accuracy overall. Such models could facilitate assessments of PWD risks. The modeling framework of this study shows potential for predicting threats from various forestry and agricultural pests. [ABSTRACT FROM AUTHOR]

Summary: Bursaphelenchus xylophilus is the causative agent of pine wilt disease and is indigenous to North America. It has been introduced into Japan where the non-pathogenic close relative, B. mucronatus , is widely distributed. Both nematode species have similar life cycles with vectors of cerambycid beetles of the genus Monochamus. When interspecific hybrids are backcrossed with B. xylophilus nematodes repeatedly, a small proportion of B. mucronatus genes is infused into the B. xylophilus genome (introgression) and may lead to adaptation to locally harsh environments. Though cool temperatures had inhibited the development of pine wilt disease, B. xylophilus started expanding the range to cool-summer areas after suspending its range expansion for 10 years in Japan. To consider if the range expansion is related to the introgression hybridisation between the two Bursaphelenchus species, some traits of newly and already formed hybrid-derived populations were compared between three temperature conditions of 16, 20 and 25°C. Formation of F1 hybrids was not affected by temperature. There was no difference in the time required for hybrid formation and for population establishment at 16°C between an interspecific crossing and two intraspecific crossings of B. xylophilus. Using three hybrid-derived populations reared over multiple generations at 25°C, there was no difference in the early rate of population growth between each of two hybrid-derived populations and its parental-lineage population of B. xylophilus at 16°C. Thus, the results did not reject a hypothesis that introgression hybridisation may have enhanced the fitness components such as pathogenicity of B. xylophilus populations at cool temperatures. [ABSTRACT FROM AUTHOR]

Pine wood nematode disease, commonly referred to as pine wilt, poses a grave threat to forest health, leading to profound ecological and economic impacts. Originating from the pine wood nematode, this disease not only causes the demise of pine trees but also casts a long shadow over the entire forest ecosystem. The accurate identification of infected trees stands as a pivotal initial step in developing effective prevention and control measures for pine wilt. Nevertheless, existing identification methods face challenges in precisely determining the disease status of individual pine trees, impeding early detection and efficient intervention. In this study, we leverage the capabilities of unmanned aerial vehicle (UAV) remote sensing technology and integrate the VGG classical small convolutional kernel network with U-Net to detect diseased pine trees. This cutting-edge approach captures the spatial and characteristic intricacies of infected trees, converting them into high-dimensional features through multiple convolutions within the VGG network. This method significantly reduces the parameter count while enhancing the sensing range. The results obtained from our validation set are remarkably promising, achieving a Mean Intersection over Union (MIoU) of 81.62%, a Mean Pixel Accuracy (MPA) of 85.13%, an Accuracy of 99.13%, and an F1 Score of 88.50%. These figures surpass those obtained using other methods such as ResNet50 and DeepLab v3+. The methodology presented in this research facilitates rapid and accurate monitoring of pine trees infected with nematodes, offering invaluable technical assistance in the prevention and management of pine wilt disease. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the genetic structures of pine wood nematodes (PWNs, Bursaphelenchus xylophilus (Steiner & Buhrer) Nickle)), in Guangdong (GD), Guangxi (GX), and Jiangsu (JS) Provinces (the major PWN dispersal centers). Furthermore, we also explored potential migration routes among the different provinces in order to provide insights into the epidemic source of PWNs in the three provinces in China. We re-sequenced a total of 241 PWNs collected from the above provinces using next-generation sequencing to obtain raw genomic data. Bioinformatics analysis was used to identify the SNPs, genetic structures, and selective sweeps of the PWNs. The results indicate that the PWNs from these three provinces can be classified into five groups (A, B, C, D, and E), among which the genetic variations are significant. All PWN strains from JS were exclusively found in Group A. The PWNs in Groups B and C were composed of strains from GD and GX, while Groups D and E comprised only GD strains. Introgression analysis identified two possible pathways: (1) from Group A to Group B-GX and (2) from Group E to Group D. Selective sweep analysis showed that in Groups B and C, the candidate genes of Group B were mainly related to pectin lyase activity. [ABSTRACT FROM AUTHOR]

Pine Wilt Disease (PWD) is a devastating pine tree disease characterized by rapid onset, high mortality rate, quick spread, and difficulty in control. Plant microbiome plays a significant role in the development of PWD. However, the endophytic microbial communities of Pinus koraiensis infected by pine wood nematode (PWN) Bursaphelenchus xylophilus remain largely unexplored. In this study, we analyzed the structural changes of endophytic communities of P. koraiensis after infection by the PWN using high-throughput sequencing technology. The results showed that the community structure underwent significant changes as the degree of PWN infection intensified. The diversity and abundance of endophytic fungi in P. koraiensis increased, while those of endophytic bacteria in P. koraiensis decreased during the infection process. Meanwhile, the abundance of some dominant microorganisms has also changed, including species such as Graphilbum and Pseudoalteromonas. Functional prediction analysis showed that the functional composition of endophytic fungi in P. koraiensis was significantly different across the development of PWD, while the composition of endophytic bacteria remained essentially similar. The results indicated that PWN infection had a significant impact on the structure, diversity, abundance, and functional gene composition of endophytic microbial communities in P. koraiensis, and most of the main endophytic microbial groups tended to coordinate with each other. This work provides a better understanding of the changes in endophytic community structure and function caused by PWD infection of P. koraiensis, which may benefit the exploration of potential endophytes for PWN biocontrol.

The global introduction of human-mediated trade and local dispersal through transport or natural pathways are major processes and contributors to biological invasion. To effectively prevent and manage biological invasion, global introduction pathways and local dispersal processes of biological invasions need to be considered as a continuum of global to local dispersal (CGLD). However, there has been no unified CGLD framework developed that simultaneously considers global introduction pathway dynamics and multiple local dispersal processes with human-mediated and natural pathways to guide the development of effective management priority strategies for pine wilt disease. In this study, we constructed a CGLD framework to evaluate the global introduction and local dispersal risks of pine wilt disease. This is an invasive forest pathogen caused by the pine wood nematode (PWN) Bursaphelenchus xylophilus, which causes severe harm to forestry ecosystems worldwide. The global introduction network dynamics has indicated that the introduction pressure of PWN continually increased during 2003–2016. The highest-risk source country and entry port were the United States and Jiangsu ports, respectively. The local dispersal modes of PWN were mainly presented a random structure with lots of “in-filling” dispersal events during 2010–2021. The PWN populations in China have gradually dispersed to non-analogous climatic regions compared to those in the native and other invasive ranges. The dispersal risk areas of PWN primarily cover southwestern, eastern, central, and northeastern China. Such integration can facilitate more accurate prediction of global introduction and local dispersal pathway risk of biological invasion and provide vital guidance for designing management priority strategies to prevent invasion.

Pine, an evergreen conifer, is widely distributed worldwide. It is economically, scientifically, and ecologically important. However, pine wilt disease (PWD) induced by the pine wood nematode (PWN) adversely affects pine trees. Many studies have been conducted on the PWN and its beetle vectors to prevent the spread of PWD. However, studies providing a comprehensive understanding of the pine tree transcriptome in response to PWN infection are lacking. Here, we performed temporal profiling of the pine tree transcriptome using PWD-infected red pine trees, Pinus densiflora, inoculated with the PWN by RNA sequencing. Our analysis revealed that defense-responsive genes involved in cell wall modification, jasmonic acid signaling, and phenylpropanoid-related processes were significantly enriched 2 weeks after PWD infection. Furthermore, some WRKY-type and MYB-type transcription factors were upregulated 2 weeks after PWD infection, suggesting that these transcription factors might be responsible for the genome-wide reprogramming of defense-responsive genes in the early PWD stage. Our comprehensive transcriptome analysis will assist in developing PWD-resistant pine trees and identifying genes to diagnose PWD at the early stage of infection, during which large-scale phenotypic changes are absent in PWD-infected pine trees. [ABSTRACT FROM AUTHOR]

Pine wilt disease (PWD), caused by pine wood nematodes, has brought a great loss in ecology and economy all over the world. In China, the forest health status is also significantly affected by PWD since 1980, especially in coniferous forests and mixed forest regions. The PWD spreads very fast and can cause a healthy pine wood tree to die within a very short time. An effective way to protect other healthy pine wood trees is to discover PWD trees early. Using unmanned aerial vehicle (UAV) images can help people discover the PWD tree quickly and accurately, and a few automatical methods have been developed to monitor PWD trees including the deep learning methods. Because of the robust spatial-temporal transferability, deep learning methods have become the mainstream algorithms to monitor PWD trees. As we know, the training dataset is the most important material to train a deep learning model. However, there is still a lack of a PWD segmentation dataset so far. To fill this gap, in this paper, we have generated the first open-sourced PWD segmentation dataset based on very high-resolution UAV images to help the community conduct PWD monitor research conveniently. This dataset has 994 training samples, and each sample has visible bands with 512 × 512 pixels, and the spatial resolution of this dataset is 0.05 m. In order to train an advanced segmentation model, we have designed a lightweight deep-learning model for mobile devices or edge devices in this manuscript, named MobileSeg. The main feature of MobileSeg is its decoupling, which uses the re-parameterization technology to improve the model performance. Finally, a large-scale real-world scenario experiment with very high-resolution UAV images was utilized to validate the performance of MobileSeg, the experiment result indicated that MobileSeg has achieved the best performance compared with the recent lightweight segmentation models, and the experiment also proved the effectiveness of the proposed PWD dataset. [ABSTRACT FROM AUTHOR]

Summary: The pine wood nematode, Bursaphelenchus xylophilus , is the cause of pine wilt disease and reproduces by copulation within host pine trees. Female mate selection in B. xylophilus mating behaviour has been reported but definitive evidence is lacking. Furthermore, while the mating behaviour of the free-living nematode Caenorhabditis elegans on agar has been well understood, the mating behaviour of B. xylophilus on agar has not been studied in detail, and the differences in their characteristics remain unclear. Here, we addressed these knowledge gaps by observing B. xylophilus mating behaviour on agar. We identified six primary mating sub-behaviours in B. xylophilus males. Comparative analysis with C. elegans revealed distinct differences in the sequence of mating stages. Notably, B. xylophilus males actively searched for the female's vulva during the wrapping stage, whereas females exhibited back-and-forth locomotion to align the male spicule with the vulva location. Additionally, we conducted mating assays using anaesthetised female nematodes to evaluate the female's role in the mating behaviours of B. xylophilus. The mating duration increased significantly when females were anaesthetised, and the probabilities of reaching the wrapping and vulva location stages were reduced. Therefore, B. xylophilus females actively cooperate in mating behaviours. Our findings highlight unique aspects of mating behaviours in B. xylophilus and provide insights concerning differences in mating behaviours between B. xylophilus and C. elegans. [ABSTRACT FROM AUTHOR]

Abstract Pine wilt disease (PWD) is a devastating forest disease caused by the pinewood nematode (PWN), Bursaphelenchus xylophilus, a migratory endoparasite that infects several coniferous species. During the last 20 years, advances have been made for understanding the molecular bases of PWN-host trees interactions. Major advances emerged from transcriptomic and genomic studies, which revealed some unique features related to PWN pathogenicity and constituted fundamental data that allowed the development of postgenomic studies. Here we review the proteomic approaches that were applied to study PWD and integrated the current knowledge on the molecular basis of the PWN pathogenicity. Proteomics has been useful for understanding cellular activities and protein functions involved in PWN-host trees interactions, shedding light into the mechanisms associated with PWN pathogenicity and being promising tools to better clarify host trees PWN resistance/susceptibility.

Bursaphelenchus mucronatus was detected in association with the pine sawyer beetle (Monochamus galloprovincialis) during the implementation and testing of cross traps with insect attractants as an efficient tool for detection survey for pine wood nematode (Bursaphelenchus xylophilus) in Bosnia and Herzegovina and Georgia in 2017 and 2018, respectively. This nematode was characterized by morphological, morphometric and molecular features. This is the first report of B. mucronatus in association with a M. galloprovincialis in Bosnia and Herzegovina and in Georgia.

Pine wilt disease (PWD) is a devastating forest disease caused by the pinewood nematode (PWN), Bursaphelenchus xylophilus, a migratory endoparasite that infects several coniferous species. During the last 20 years, advances have been made for understanding the molecular bases of PWN-host trees interactions. Major advances emerged from transcriptomic and genomic studies, which revealed some unique features related to PWN pathogenicity and constituted fundamental data that allowed the development of postgenomic studies. Here we review the proteomic approaches that were applied to study PWD and integrated the current knowledge on the molecular basis of the PWN pathogenicity. Proteomics has been useful for understanding cellular activities and protein functions involved in PWN-host trees interactions, shedding light into the mechanisms associated with PWN pathogenicity and being promising tools to better clarify host trees PWN resistance/susceptibility. [ABSTRACT FROM AUTHOR]

Simple Summary: Pine wilt disease is a devastating disease, and its causal pathogen, pine wood nematode (PWN), is extremely challenging to manage. This study identified that PWN enters cryptobiosis under high-osmotic-pressure stress. The phenotypic changes and survival of the nematodes during each developmental stage were significantly different. Among them, the third-stage dispersal juvenile had the highest survival and body length change rates. By comparing the gene expression differences between the third-stage dispersal juvenile and other stages, it was found that they exhibited expression differences in genes in energy compound synthesis and anti-reversal signal pathway. The results of this study provide a theoretical basis for the prevention and treatment of PWN by exploiting the differences in high osmotic pressure tolerance at different developmental stages. Under ion imbalance, water deficiency, and salt stress, the osmotic pressure of the tree sap increases, and pine wood nematodes (Bursaphelenchus xylophilus, PWN) parasitizing in the trees may be subjected to high-osmotic-pressure stress. KCl, L-malic acid, sucrose, and glycerol solutions were used as osmolytes to explore the highest osmotic concentration that PWN can tolerate. Survival analysis showed that when the treatment concentration exceeded 90%, only a few nematodes in the glycerol group survived under 6 h treatment, and most of the survivors were third-stage dispersal juveniles (DJ3). Further examination revealed that under different concentrations of glycerol-induced high osmotic pressure, the survival rate and body length change rate were the highest in the DJ3 and the lowest in the second-stage propagative juveniles. In order to explore the molecular mechanism of resistance of DJ3 to high osmotic stress, transcriptome sequencing was performed at each developmental stage of PWN and differentially expressed genes that were up-regulated or down-regulated only in DJ3 were screened. The expression of genes related to CoA in DJ3, a key enzyme in metabolism, was significantly higher than the other developmental stages. In addition, the expression of the anti-reversal signal pathway-related gene AKT-1 in DJ3 was significantly lower than in the other development stages. Therefore, the specific expression of genes in DJ3 under high osmotic pressure may help them rapidly produce and accumulate energy-related compounds and activate the adenosine 5′-monophosphate (AMP)-activated protein kinase (AMPK) pathway to respond to damage caused by high-osmotic-pressure stress in time, thus promoting survival. [ABSTRACT FROM AUTHOR]

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Summary: The pine wood nematode, Bursaphelenchus xylophilus (Steiner et Buhrer), is the causative agent of pine wilt disease. It is native to North America and has been devastating pine forests in East Asia and West Europe since its introduction. The pathogenic nematode is transmitted by cerambycid beetle adults of Monochamus alternatus Hope in East Asia and M. galloprovincialis (Olivier) in West Europe. Bursaphelenchus mucronatus Mamiya et Enda is widely distributed in Eurasia and has no or little pathogenicity to pine species. If hybrids between the two species are backcrossed with B. xylophilus nematodes repeatedly, a small proportion of B. mucronatus genes will be infused into B. xylophilus genome (introgression) and may lead to adaptation to locally harsh environments. Inoculation tests in this study revealed that two of eight hybrid-derived populations from crossing B. xylophilus and B. mucronatus caused pine seedling mortalities of 36-70%. The pathogenic hybrid-derived populations carried nuclear ribosomal DNA (rDNA) of two species and B. xylophilus extra-nuclear genes, whereas non-pathogenic populations carried B. mucronatus rDNA and extranuclear genes of B. xylophilus or B. mucronatus. Thus, it is inferred that a gene or genes associated with pathogenicity are present in the nuclear genome of B. xylophilus. A laboratory experiment revealed that the pathogenic hybrid-derived population had as great an ability to board M. alternatus adults as the parental-lineage B. xylophilus isolate. Thus, the introgressive hybridisation is considered to occur in pine forests if two species cohabit in host trees. [ABSTRACT FROM AUTHOR]

Pine wilt disease (PWD) is a highly contagious and devastating forest disease. The timely detection of pine trees infected with PWD in the early stage is of great significance to effectively control the spread of PWD and protect forest resources. However, in the spatial domain, the features of early-stage PWD are not distinctly evident, leading to numerous missed detections and false positives when directly using spatial-domain images. However, we found that frequency domain information can more clearly express the characteristics of early-stage PWD. In this paper, we propose a detection method based on deep learning for early-stage PWD by comprehensively utilizing the features in the frequency domain and the spatial domain. An attention mechanism is introduced to further enhance the frequency domain features. Employing two deformable convolutions to fuse the features in both domains, we aim to fully capture semantic and spatial information. To substantiate the proposed method, this study employs UAVs to capture images of early-stage pine trees infected with PWD at Dahuofang Experimental Forest in Fushun, Liaoning Province. A dataset of early infected pine trees affected by PWD is curated to facilitate future research on the detection of early-stage infestations in pine trees. The results on the early-stage PWD dataset indicate that, compared to Faster R-CNN, DETR and YOLOv5, the best-performing method improves the average precision (AP) by 17.7%, 6.2% and 6.0%, and the F1 scores by 14.6%, 3.9% and 5.0%, respectively. The study provides technical support for early-stage PWD tree counting and localization in the field in forest areas and lays the foundation for the early control of pine wood nematode disease. [ABSTRACT FROM AUTHOR]

The pine wood nematode (PWN) is one of the most threatening pests of pine forests in China. An essential management response involves felling and removing the infested trees before the PWN can spread over large areas, but this requires early detection. In this study, we analyzed the temporal changes in the spectral signatures of healthy and infested trees throughout the entire growing season (May to October) using unmanned aerial vehicle (UAV) hyperspectral images (HSI). To explore the potential of these seasonal spectral changes in detecting PWN, we investigated the separability of healthy and infested trees using both absolute values and changes in values. A random forest (RF) classifier was applied to separate healthy and infested trees based on reflectances, derivatives, vegetation indices (VIs), and their seasonal change values. We obtained the following results: (1) the seasonal changes of tree crown spectra following a PWN infestation were similar to those observed using absolute spectral values, though the latter performed better in early detection; (2) in the early stage of infestation (June and July), the green and red-edge regions contained the most sensitive bands, whereas the near-infrared portion played a more important role in later stages; (3) derivatives achieved higher overall accuracy (OA) than the reflectance in the early stage of PWN infestation (June and July); (4) in June, the Pigment Specific Simple Ratio (PSSR) had the highest separability (OA = 0.77) for PWN infestation, followed by the Plant Senescence Reflectance Index (PSRI) and the Normalized Difference Red-edge Index (NDRE), both with a OA of 0.70. In July, PSRI, Red Edge Normalized Difference Vegetation Index (RENDVI), and the Modified Red Edge Simple Ratio (MRESR) had the highest OA of 0.77. These VIs were calculated based on the red-edge regions. In August, RENDVI achieved the best accuracy (0.87), followed by the Normalized Difference Vegetation Index (NDVI, OA = 0.83) and the Plant Stress Index (PSI, OA = 0.80). In September and October, PSRI, PSI, the Greenness Index (GI), and RENDVI showed the strongest separability (0.87 to 0.90). Similar results were obtained using change values of VIs. In June, RENDVI, PSI, and NDVI showed the highest accuracy (OA = 0.73). In July, MRESR had the best accuracy (0.77), followed by RENDVI (0.73) and PSI (0.73). In the late stage of PWN infestation, NDVI, PSRI, PSI, RENDVI, GI, and PSSR obtained the highest accuracies (0.83 to 0.93), surpassing the accuracy achieved using absolute spectra; (5) in RF classification model, seasonal variation values derived from reflectances, derivatives, and VIs performed well in the late stages of the PWN infestation (September and October) but were not as good as absolute values in the early and middle stages (June to August). Our study explored the potential of seasonal changes in UAV spectra for early detection of forest pests.

Abstract Background The pinewood nematode is the causal agent of the pine wilt disease, which causes severe ecological and economic losses in coniferous forests. The invasion of pine wood nematode has undergone various rapid adaptations to a wide range of temperatures and to new hosts and vector insects. DNA methylation may play crucial roles in the rapid adaptation of PWN during invasion. However, whether the PWN genome contins functional DNA modifications remains elusive. Results Here, we detected the extensive presence of 5-methylcytosine (5mC) and N6-methyladenine (6mA) in the B. xylophilus genome, with low methylation levels at most positions. Cytosines were methylated in the CpG, CHG. and CHH sequence contexts, with the lowest methylation levels at CpG sites. The methylation levels of CpG and 6mA in gene regions showed opposite trends. The changes in the abundance of 5mC and 6mA showed the same trends in response to temperature change, but opposite trends during development. Sequence and phylogenetic analyses showed that the proteins BxDAMT and BxNMAD have typical characteristics of a methylase and demethylase, respectively, and are conserved among species. Conclusions These findings shed light on the epigenetic modifications present in the genome of PWN, and will improve our understanding of its invasiveness and evolution.

Monochamus saltuarius Gebler is a serious insect pest in Europe and East Asia regions, including Portugal, Spain, China, Japan, and Korea. It transfers the pine wood nematode Bursaphelenchus xylophilus to conifer trees, resulting in pine wilt disease (PWD). As temperature is a key factor influencing insect population dynamics, temperature-dependent models describing M. saltuarius oviposition could estimate population growth potential and evaluate outbreak risks. In this study, the longevity and fecundity of M. saltuarius females were measured under constant temperature conditions ranging from 20 to 32 °C, and temperature-dependent models were constructed. The longevity of M. saltuarius females ranged from 83.36 days to 22.92 days, with a total fecundity of 141 eggs and 52.77 eggs at 20 °C and 32 °C, respectively. To describe oviposition, we used a single-phase simulation describing oviposition as a single model and a two-phase simulation describing sexual maturation and oviposition as two separate models. These models effectively described M. saltuarius oviposition (r2 > 0.96) under constant temperature conditions, with the two-phase simulation demonstrating greater accuracy overall. Such models could facilitate assessments of PWD risks. The modeling framework of this study shows potential for predicting threats from various forestry and agricultural pests.

Pine wood nematode disease, commonly referred to as pine wilt, poses a grave threat to forest health, leading to profound ecological and economic impacts. Originating from the pine wood nematode, this disease not only causes the demise of pine trees but also casts a long shadow over the entire forest ecosystem. The accurate identification of infected trees stands as a pivotal initial step in developing effective prevention and control measures for pine wilt. Nevertheless, existing identification methods face challenges in precisely determining the disease status of individual pine trees, impeding early detection and efficient intervention. In this study, we leverage the capabilities of unmanned aerial vehicle (UAV) remote sensing technology and integrate the VGG classical small convolutional kernel network with U-Net to detect diseased pine trees. This cutting-edge approach captures the spatial and characteristic intricacies of infected trees, converting them into high-dimensional features through multiple convolutions within the VGG network. This method significantly reduces the parameter count while enhancing the sensing range. The results obtained from our validation set are remarkably promising, achieving a Mean Intersection over Union (MIoU) of 81.62%, a Mean Pixel Accuracy (MPA) of 85.13%, an Accuracy of 99.13%, and an F1 Score of 88.50%. These figures surpass those obtained using other methods such as ResNet50 and DeepLab v3+. The methodology presented in this research facilitates rapid and accurate monitoring of pine trees infected with nematodes, offering invaluable technical assistance in the prevention and management of pine wilt disease.

Clearing diseased wood is a common measure used to reduce the continued spread of pine wilt disease and prevent infecting other pines. However, the impact of clearing diseased wood on the physicochemical properties of the soil is still unclear. To elucidate this matter, we conducted a series of soil experiments and observations in Changdao, mainly focused on uncut black pine, cut black pine, and the inter-forest zone. The results showed the following. (1) The soil beneath the forest underwent a transition towards the characteristics of forest and grassland after clearing diseased wood, which indicated a potential shift in the ecosystem's structure and function. (2) Clearing diseased wood led to an increase in the soil pH of 0.15, indicating that it facilitated the recovery of acidic soil. (3) The clearing of diseased wood can coarsen the soil's texture. Moreover, it effectively reduced the surface soil temperature (0–20 cm) in summer by 1.52 °C, as well as significantly decreasing the surface (0–20 cm) soil moisture in spring and summer by 1.3% and 2.43%, respectively. (4) Clearing diseased wood clearing can effectively modify the content of essential nutrients in the soil. It reduced the available nitrogen by 26.86 mg·kg−1, increased the available phosphorus by 0.57 mg·kg−1, and decreased the available potassium by 1.68 mg·kg−1. Meanwhile, clearing diseased wood exacerbated soil salinization and increased the soil's salt content by 0.70 g·kg−1. The findings of this study provide scientific solutions for the sustainable ecological development of black pine forests in Changdao. [ABSTRACT FROM AUTHOR]

Background: The pinewood nematode is the causal agent of the pine wilt disease, which causes severe ecological and economic losses in coniferous forests. The invasion of pine wood nematode has undergone various rapid adaptations to a wide range of temperatures and to new hosts and vector insects. DNA methylation may play crucial roles in the rapid adaptation of PWN during invasion. However, whether the PWN genome contins functional DNA modifications remains elusive. Results: Here, we detected the extensive presence of 5-methylcytosine (5mC) and N6-methyladenine (6mA) in the B. xylophilus genome, with low methylation levels at most positions. Cytosines were methylated in the CpG, CHG. and CHH sequence contexts, with the lowest methylation levels at CpG sites. The methylation levels of CpG and 6mA in gene regions showed opposite trends. The changes in the abundance of 5mC and 6mA showed the same trends in response to temperature change, but opposite trends during development. Sequence and phylogenetic analyses showed that the proteins BxDAMT and BxNMAD have typical characteristics of a methylase and demethylase, respectively, and are conserved among species. Conclusions: These findings shed light on the epigenetic modifications present in the genome of PWN, and will improve our understanding of its invasiveness and evolution. [ABSTRACT FROM AUTHOR]

Pine wilt disease (PWD), which is caused by the Bursaphelenchus xylophilus, is one of the most serious biological invasions in East Asia. Removal of infected pine trees is generally used to prevent the spread of PWD. However, how this strategy affects plant species diversity and ecosystem functions needs to be clarified. We compared alpha diversity, species composition, and biomass for all woody plant species, adults, saplings, and seedlings in infected Masson pine forests where removal of infected trees occurred (CTD) and where infected trees were retained (UTD), uninfected Masson pine forests (PMF), and evergreen broad-leaved forests (EBF). UTD had the highest alpha diversity of all species and saplings, and UTD and PMF had the lowest alpha diversity of seedlings. CTD and EBF had a similar composition of seedlings, and CTD and UTD had similar species composition of all plant species and saplings. UTD had the lowest biomass for all species and adults but had the highest saplings biomass. Soil properties were significantly related to plant biomass. The retention of infected trees likely maintained soil fertility which increased species alpha diversity and the biomass of saplings, and unchanged species composition compared to the removal of infected trees, indicating that the retention strategy could help to maintain ecosystem functions. [ABSTRACT FROM AUTHOR]

(1) Pine wilt disease (PWD) is a devastating disease of pine forests caused by the pine wood nematode (PWN), Bursaphelenchus xylophilus. Control of the disease is a worldwide problem due to the impossibility of using chemical nematicides on a large scale and for long periods. (2) Based on preliminary tests of microemulsion quality and stability, the optimum formulation was selected from 14 formulated microemulsions. The median lethal concentration (LC50) of the selected formulation at 48 h after treatment of B. xylophilus was 31.45 μg/mL of emamectin benzoate. The active ingredient reached the apical branches of Pinus thunbergii within 90 days of injection. (3) P. thunbergii was inoculated with B. xylophilus at 100 days post-injection, and the trees treated with the formulation remained uninfected for 450 days. Trunk injection exerted substantial control over PWD. (4) These results indicate that this formulation has the advantages of good transportability and long persistence in pine trees after injection and that it effectively prevents PWD. Therefore, this emamectin benzoate formulation can effectively reduce PWD occurrence in pine forests. [ABSTRACT FROM AUTHOR]

Graphilbum species are important blue stain fungi associated with pine trees and are widely distributed throughout Asia, Australia, and North Africa. Pine wood nematode (PWN) primarily feed on ophiostomatoid fungi such as Graphilbum sp. in wood, the population of PWNs was increased, and incomplete organelle structures were observed in Graphilbum sp. hyphal cells following exposure to PWNs. In this study, we showed that Rho and Ras were involved in the MAPK pathway, SNARE binding and small GTPase‐mediated signal transduction, and their expression was upregulated in the treatment group. However, the expression of the Rab7 involved in MAPK and small GTPase‐mediated signal pathway was downregulated in the treatment group. Thus, further research is needed to study the MAPK pathway and related Ras and Rho genes in Graphilbum sp. associated with the PWN population. Overall, transcriptomic analysis clarified the basic mechanisms of mycelial growth in Graphilbum sp. fungus used as a food source by PWNs. [ABSTRACT FROM AUTHOR]

To solve the system of differential equations which represents the present pine wilt disease epidemic model, we use the computational algorithms like the differential transform method, and it is a multi-step approach. Description of proposed transformations is constructed at first. Then ODEs of the proposed Epidemic Model are utilized to build the mathematical model. Obtaining the reliable approximate solutions in the larger domain had been succeeded in the multi-step differential transform method than in the differential transform method, since local convergence of the Taylor series assures that an initial condition is updated in each subdomain, so the error is minimized in a larger domain. The efficiency of this method is discussed and a reasonable solution for differential transform method, as well as for multi-step differential transform method is obtained. Further, the obtained solutions are compared with the RK4 method, they numerically coincide. [ABSTRACT FROM AUTHOR]

Summary: The pine wood nematode (PWN), Bursaphelenchus xylophilus , is the causative agent of pine wilt disease and is transmitted primarily by cerambycid adults of the genus Monochamus. It is believed to have been introduced into Japan from North America in the 1900s and confirmed to have invaded western Europe in 1999. The nematode has been devastating pine forests in invaded areas because the native pine species are susceptible. This study examined the number of PWN carried by individual M. carolinensis adults (initial PWN load) immediately after emerging from dead Pinus sylvestris and P. strobus trees in Illinois, USA. The data were compared with the initial PWN load on M. alternatus adults emerging from dead P. thunbergii trees in Japan ca 80 years after the PWN invasion. When the zero-inflated negative binomial model was fitted to the initial PWN loads it provided three results. First, the PWN exhibited clumped distributions among vectors in the PWN- M. carolinensis - P. sylvestris or P. strobus system in Illinois and the PWN- M. alternatus - P. thunbergii system in Japan. Second, there was no difference in the frequency distribution of the initial PWN load between the three disease systems. Third, the initial PWN load increased as the overwintering PWN density in wood or the adult body mass increased, whereas it decreased as the emergence date of vectors increased. Consequently, the frequency distribution of initial PWN load exhibited no evolutionary change in Japan and the initial PWN load was considered to be determined by environmental factors and conditions. [ABSTRACT FROM AUTHOR]

Under ion imbalance, water deficiency, and salt stress, the osmotic pressure of the tree sap increases, and pine wood nematodes (Bursaphelenchus xylophilus, PWN) parasitizing in the trees may be subjected to high-osmotic-pressure stress. KCl, L-malic acid, sucrose, and glycerol solutions were used as osmolytes to explore the highest osmotic concentration that PWN can tolerate. Survival analysis showed that when the treatment concentration exceeded 90%, only a few nematodes in the glycerol group survived under 6 h treatment, and most of the survivors were third-stage dispersal juveniles (DJ3). Further examination revealed that under different concentrations of glycerol-induced high osmotic pressure, the survival rate and body length change rate were the highest in the DJ3 and the lowest in the second-stage propagative juveniles. In order to explore the molecular mechanism of resistance of DJ3 to high osmotic stress, transcriptome sequencing was performed at each developmental stage of PWN and differentially expressed genes that were up-regulated or down-regulated only in DJ3 were screened. The expression of genes related to CoA in DJ3, a key enzyme in metabolism, was significantly higher than the other developmental stages. In addition, the expression of the anti-reversal signal pathway-related gene AKT-1 in DJ3 was significantly lower than in the other development stages. Therefore, the specific expression of genes in DJ3 under high osmotic pressure may help them rapidly produce and accumulate energy-related compounds and activate the adenosine 5′-monophosphate (AMP)-activated protein kinase (AMPK) pathway to respond to damage caused by high-osmotic-pressure stress in time, thus promoting survival.

Pinus massoniana Lamb. is a crucial timber and resin conifer in China, but its plantation industry is threatened by outbreaks of pine wilt disease (PWD) caused by Bursaphelenchus xylophilus (pinewood nematode; PWN). However, as of yet, there is no comprehensive analysis of NBS-LRR genes in P. massoniana involved in its defense against PWN. In this study, 507 NBS genes were identified in the transcriptome of resistant and susceptible P. masoniana inoculated with the PWN. The phylogenetic analysis and expression profiles of resistant and susceptible P. massoniana revealed that the up-regulated PmNBS-LRR97 gene was involved in conferring resistance to PWN. The results of real-time quantitative PCR (qRT-PCR) showed that PmNBS-LRR97 was significantly up-regulated after PWN infection, especially in the stems. Subcellular localization indicated that PmNBS-LRR97 located to the cell membrane. PmNBS-LRR97 significantly activated the expression of reactive oxygen species (ROS)-related genes in P. massoniana. In addition, the overexpression of PmNBS-LRR97 was capable of promoting the production of ROS, aiding in plant growth and development. In summary, PmNBS-LRR97 participates in the defense response to PWN and plays an active role in conferring resistance in P. massoniana. This finding provides new insight into the regulatory mechanism of the R gene in P. massoniana. [ABSTRACT FROM AUTHOR]

Pine wilt disease (PWD) caused by the pine wood nematode (PWN) is China's most serious forest disease in recent decades. Its complex disease system with unclear pathogenesis and differentiated pathogenicity makes it challenging to manage and control. PWD has spread rapidly in Northeast and Northwest China in recent years, exceeding previous predictions and the traditional understanding of its potential distribution. This paper reviewed the comprehensive risk of PWD in Northeast and Northwest China through the occurrence of influencing factors. Regarding PWN's temperature resistance, all regions of China are suitable for PWD. In terms of altitude, the PWD system is mainly distributed below 1000 m. In China, Pinus and Larix species are confirmed host trees of PWN, while Monochamus alternatus and M. saltuarius are confirmed vector insects of PWN. In this case, PWD may occur in all low-altitude pine forests in China. Northeast China has a higher risk than Northwest China due to its distribution of suitable host trees and vector beetles at low altitudes. To confront the threat, two scientific bottlenecks are required to be demonstrated. The first is the pathogenicity of Chinese PWN strains to Chinese Picea and Abies species. The other is the geographical distribution and highest altitude distribution of other Monochamus species in the Palaearctic region of China and their PWN transmission ability. We also suggest strengthening plant quarantining in Northeast China. In conclusion, this review comprehensively analyzes the risk of PWD in Northeast and Northwest China in terms of temperature, altitude, host trees, and vector insects. It provides a new perspective and reference for the management and research of PWD in China. [ABSTRACT FROM AUTHOR]

Under the strong influence of climate change and human activities, the frequency and intensity of disturbance events in the forest ecosystem both show significant increasing trends. Pine wood nematode (Bursapherenchus xylophilus, PWN) is one of the major alien invasive species in China, which has rapidly infected the forest and spread. In recent years, its tendency has been to spread from south to north, causing serious losses to Pinus and non-Pinus coniferous forests. It is urgent to carry out remote sensing monitoring and prediction of pine wilt disease (PWD). Taking Anhui Province as the study area, we applied ground survey, satellite-borne optical remote sensing imagery and environmental factor statistics, relying on the Google Earth Engine (GEE) platform to build a new vegetation index NDFI based on time-series Landsat images to extract coniferous forest information and used a random forest classification algorithm to build a monitoring model of the PWD infection stage. The results show that the proposed NDFI differentiation threshold classification method can accurately extract the coniferous forest range, with the overall accuracy of 87.75%. The overall accuracy of the PWD monitoring model based on random forest classification reaches 81.67%, and the kappa coefficient is 0.622. High temperature and low humidity are conducive to the survival of PWN, which aggravates the occurrence of PWD. Under the background of global warming, the degree of PWD in Anhui Province has gradually increased, and has transferred from the southwest and south to the middle and northeast. Our results show that PWD monitoring and prediction at a regional scale can be realized by using long time-series multi-source remote sensing data, NDFI index can accurately extract coniferous forest information and grasp disease information in a timely manner, which is crucial for effective monitoring and control of PWD. [ABSTRACT FROM AUTHOR]

Monochamus saltuarius (Coleoptera: Cerambycidae) was reported as the vector beetle of the pine wood nematode (PWN, Bursaphelenchus xylophilus) in Japan and Europe. It was first reported to transmitted the PWN to native Pinus species in 2018 in Liaoning Province, China. However, the lack of genomic resources has limited the in-depth understanding of its interspecific relationship with PWN. Here, we obtained a chromosome-level reference genome of M. saltuarius combining Illumina, Nanopore and Hi-C sequencing technologies. We assembled the scaffolds into ten chromosomes (including an X chromosome) and obtained a 682.23 Mb chromosome-level genome with a N50 of 73.69 Mb. In total, 427.67 Mb (62.69 %) repeat sequences were identified and 14, 492 protein-coding genes were predicted, of which 93.06 % were annotated. We described the mth / mthl , P450, OBP and OR gene families associated with the vector beetle's development and resistance, as well as the host selection and adaptation, which serve as a valuable resource for understanding the host adaptation in insects during evolution. This high quality reference genome of M. saltuarius also provide new avenues for researching the mechanism of this synergistic damage between vector beetles and PWN. • This research assembled the first chromosomal-level reference genome of Monochamus saltuarius. • The sex chromosome was identified. • Inferred the evolutionary relationship of currently sequenced Coleoptera species. • The contraction and expansion of gene families associated with the insect host adaptation were explored. • We identified the most methuselah/methuselah-like genes associated with insect development and lifespan in M. saltuarius. [ABSTRACT FROM AUTHOR]

Transcription factors (TFs) are a class of proteins that play an important regulatory role in controlling the expression of plant target genes by interacting with downstream regulatory genes. The lateral organ boundary (LOB) structural domain (LBD) genes are a family of genes encoding plant-specific transcription factors that play important roles in regulating plant growth and development, nutrient metabolism, and environmental stresses. However, the LBD gene family has not been systematically identified in Pinus massoniana, one of the most important conifers in southern China. Therefore, in this study, we combined cell biology and bioinformatics approaches to identify the LBD gene family of P. massoniana by systematic gene structure and functional evolutionary analysis. We obtained 47 LBD gene family members, and all PmLBD members can be divided into two subfamilies, (Class I and Class II). By treating the plants with abiotic stress and growth hormone, etc., under qPCR-based analysis, we found that the expression of PmLBD genes was regulated by growth hormone and abiotic stress treatments, and thus this gene family in growth and development may be actively involved in plant growth and development and responses to adversity stress, etc. By subcellular localization analysis, PmLBD is a nuclear protein, and two of the genes, PmLBD44 and PmLBD45, were selected for functional characterization; secondly, yeast self-activation analysis showed that PmLBD44, PmLBD45, PmLBD46 and PmLBD47 had no self-activating activity. This study lays the foundation for an in-depth study of the role of the LBD gene family in other physiological activities of P. massoniana. [ABSTRACT FROM AUTHOR]

Pine wilt disease (PWD) has caused extensive mortality in pine forests worldwide. The longicorn beetle Monochamus saltuarius, as the vector of the invasive species Bursaphelenchus xylophilus, plays an important role in the infection cycle. Although the gut microbiota and its contribution to health and disease have been extensively documented, it is unclear whether B. xylophilus affects the longicorn gut microbiota because of a lack of understanding of potential temporal changes in the microbial composition of the vector beetles. In this study, we collected beetles at the emergence and mating stages, and divided them into two groups according to whether they carried nematodes. Based on 16S rDNA sequence analysis, 174 bacterial species were identified that belonged to 112 genera, 53 families, and 8 phyla. Bursaphelenchus xylophilus increased the microflora abundance and diversity of the infected M. saltuarius. In addition, Firmicutes and Bacteroidetes were more abundant in infected M. saltuarius at the same developmental stage. Some of the bacteria in these two phyla were the key species in the co-occurrence network of intestinal flora and represented a unique module in the co-occurrence network of infected M. saltuarius. We found some high abundance colonies in the intestinal tract of infected M. saltuarius during the emergence period that were mostly related to metabolism. Compared with the emergence period, there were more similar microorganisms in the intestinal tract of M. saltuarius during the mating period. With the change in growth environment and continuous feeding, the intestinal microorganisms gradually stabilized and became single species. [ABSTRACT FROM AUTHOR]

Plant resistance (R) genes play a crucial role in the detection of effector proteins secreted by pathogens, either directly or indirectly, as well as in the subsequent activation of downstream defence mechanisms. However, little is known about how R genes regulate the defence responses of conifers, particularly Pinus massoniana, against the destructive pine wood nematode (PWN; Bursaphelenchus xylophilus). Here, we isolated and characterised PmHs1 pro-1 , a nematode-resistance gene of P. massoniana, using bioinformatics, molecular biology, histochemistry and transgenesis. Tissue-specific expressional pattern and localisation of PmHs1 pro-1 suggested that it was a crucial positive regulator in response to PWN attack in resistant P. massoniana. Meanwhile, overexpression of PmHs1 pro-1 was found to activate reactive oxygen species (ROS) metabolism-related enzymes and the expressional level of their key genes, including superoxide dismutase, peroxidase and catalase. In addition, we showed that PmHs1 pro-1 directly recognised the effector protein BxSCD1of PWN, and induced the ROS burst responding to PWN invasion in resistant P. massoniana. Our findings illustrated the molecular framework of R genes directly recognising the effector protein of pathology in pine, which offered a novel insight into the plant-pathogen arms race., (© 2024 John Wiley & Sons Ltd.)

Pine wilt disease (PWD) is one of the most devastating diseases of Pinus spp. and is caused by the pine wood nematode (PWN), Bursaphelenchus xylophilus (Steiner & Buhrer) Nickle. To study adaptation of PWN to survive in hosts that differ in resistance, we examined the self-regulatory characteristics of PWN at the biological and molecular levels early in the interaction. Two-year-old susceptible Pinus thunbergii and resistant Pinus taeda were selected for this experiment, and changes in PWNs after inoculation were assessed. qRT-PCR was used to detect changes in genes related to PWN pathogenicity and detoxification. The results showed that the migration and reproductive abilities of PWNs in P. thunbergii were stronger than those of PWNs in P. taeda. After 7 d, the number of nematodes in P. thunbergii was approximately 3.2-fold higher than in P. taeda. After 15 d, the number of nematodes in P. thunbergii was approximately twofold higher than that in P. taeda. Because PWN can adjust its sex ratio after infection, we compared the sex ratio of uninoculated PWNs, to that in the two pine species. In P. thunbergii, the female to male ratio first decreased and then stabilized over time; in P. taeda first decreased and then increased. Relative fat accumulation in PWNs increased significantly after the PWNs entered the tree body; the accumulation rate in P. thunbergii was higher than in P. taeda at 7 d, but lower after 15 d. Scanning electron microscopy (SEM) showed significantly more bacteria on the surface of PWNs in P. taeda compared with PWNs in susceptible P. thunbergii. At 12 h after inoculation, the expression of genes related to cell-wall degradation (BxBeta1-4 and Bxpel1), effectors (BxCDP1, BxSapB1), and active oxygen metabolism (Bxy-ctl-1 and BxGST3) was 2–6 × higher in the resistant pine than in the susceptible one. In contrast, in PWNs, the expression of autophagy-related genes BxATG1 and BxATG16 was 1.5–2 times higher in P. thunbergii than in P. taeda. These results indicate that the interaction between PWNs and pine trees with different resistance levels elicits a series of physiological and molecular adaptations that affect nematode reproduction and virulence. This study will help elucidate the adaptive mechanisms of PWN in different pine trees. [ABSTRACT FROM AUTHOR]

Pine wood nematode, Bursaphelenchus xylophilus, as one of the greatest threats to pine trees, is spreading all over the world. Plant microorganisms play an important role in the pathogenesis of nematodes. The phyllosphere and rhizosphere bacterial and fungal communities associated with healthy Pinus koraiensis (PKa) and P. koraiensis infected by B. xylophilus at the early (PKb) and last (PKc) stages were analyzed. Our results demonstrated that pine wood nematode (PWD) could increase the phyllosphere bacterial Pielou_e, Shannon, and Simpson index; phyllosphere fungal Chao 1 index, as well as rhizosphere bacterial Pielou_e, Shannon, and Simpson index; and rhizosphere fungal Pielou_e, Shannon, and Simpson index. What's more, slight shifts of the microbial diversity were observed at the early stage of infection, and the microbial diversity increased significantly as the symptoms of infection worsened. With the infection of B. xylophilus in P. koraiensis, Bradyrhizobium (rhizosphere bacteria), Massilia (phyllosphere bacteria), and Phaeosphaeriaceae (phyllosphere fungi) were the major contributors to the differences in community compositions among different treatments. With the infection of PWD, most of the bacterial groups tended to be co-excluding rather than co-occurring. These changes would correlate with microbial ability to suppress plant pathogen, enhancing the understanding of disease development and providing guidelines to pave the way for its possible management. [ABSTRACT FROM AUTHOR]

An ethanol extract of I N. incisum i rhizomes showed LD SB 50 sb values at 0.045 mg ml SP -1 sp against PWN, and falcaridiol, falcarinol, isoimperatorin, and columbianetin were responsible for its nematicidal activity (Liu I et al. i , 2016). The biological activity of I C. majus i var. I asiaticum i on insects and fungi has been reported (Zou I et al. i , 2017; Wei I et al. i , 2020). Kim I et al. i (2011a) and Nguyen I et al. i (2009) reported that extracts of Korean domestic plants and medicinal plant extracts did not show >60% nematicidal activity at 2.5 mg ml SP -1 sp and 4.0 mg ml SP -1 sp concentrations, respectively. Keywords: botanical pesticide; pine wilt disease; pine wood nematode; Pinus EN botanical pesticide pine wilt disease pine wood nematode Pinus 837 840 4 09/30/22 20220701 NES 220701 The pine wood nematode (PWN), I Bursaphelenchus xylophilus i (Steiner & Buhrer), causes pine wilt disease (PWD), which is the most severe disease of pine forests worldwide (Mota & Vieira, 2008). [Extracted from the article]

Pinus massoniana is a pioneer species for afforestation timber and oleoresin, while epidemics of pinewood nematode (PWN; Bursaphelenchus xylophilus) are causing a serious biotic disaster for P. massoniana in China. Importantly, resistant P. massoniana could leak copious oleoresin terpenoids to build particular defense fronts for survival when attacked by PWN. However, the defense mechanisms regulating this process remain unknown. Here, PmCYP720B11v2, a cytochrome P450 monooxygenase gene, was first identified and functionally characterized from resistant P. massoniana following PWN inoculation. The tissue-specific expression pattern and localization of PmCYP720B11v2 at the transcript and protein levels in resistant P. massoniana indicated that its upregulation in the stem supported its involvement in the metabolic processes of diterpene biosynthesis as a positive part of the defense against PWN attack. Furthermore, overexpression of PmCYP720B11v2 may enhance the growth and development of plants. In addition, PmCYP720B11v2 activated the metabolic flux of antioxidases and stress-responsive proteins under drought conditions and improved drought stress tolerance. Our results provide new insights into the favorable role of PmCYP720B11v2 in diterpene defense mechanisms in response to PWN attack in resistant P. massoniana and provide a novel metabolic engineering scenario to reform the stress tolerance potential of tobacco. [ABSTRACT FROM AUTHOR]

Summary: The pine wood nematode (PWN), Bursaphelenchus xylophilus , is the causative agent of pine wilt disease and is transmitted by cerambycid adults of the genus Monochamus. It is believed to have been introduced into Japan from North America in the 1900s and since then it has been devastating the native pine forests. By contrast, the epidemics of the disease have never occurred in pine forests native to North America in the original habitats, indicating no expression of virulence. To determine the evolutionary change in the transmission traits of PWN, the temporal pattern of PWN transmission to fresh branch sections of Pinus sylvestris was studied using 38 Monochamus carolinensis adults in Illinois, USA, and compared with previous studies on the PWN- M. alternatus and B. mucronatus - M. saltuarius systems in Japan. A great difference was observed in the initial nematode load among vectors irrespective of the three systems. The maximal numbers of PWN transmitted (5 days)−1 by individual vectors were greater and the efficiencies of nematode transmission and invasion were higher for the Japanese PWN- M. alternatus system than for the North American PWN- M. carolinensis system in two heavy classes of initial load of over 1000 nematodes. The proportion of PWN transmitted to healthy pine trees by reproductively immature female vectors was small (2.5-11.5%) in the three nematode-vector systems in most cases. The evolutionary changes in the transmission traits and the control of the range expansion of the PWN were discussed in relation to the expression of virulence. [ABSTRACT FROM AUTHOR]

Abstract Background Recently, pine wood nematode (PWN, Bursaphelenchus xylophilus) has been found in the extreme cold area of northeast China. The third-stage dispersal juvenile (DJ3) of PWN, which is a long-lived stress-resistant stage, plays an important role in the process of PWN spreading to low-temperature areas, as this stage can survive under unfavorable conditions. Results Weighted correlation network analysis (WGCNA) was used to analyze the expression patterns of 15,889 genes included in 21 RNA-Seq results of PWN at DJ3 and the other 6 different stages, and a total of 12 coexpression modules were obtained. Among them, the magenta module has the highest correlation with DJ3, which included a total of 652 genes. KEGG enrichment analysis showed that most of the genes in the magenta module were involved in metabolic processes, which were related to autophagy and longevity regulation. These pathways included starch and sucrose metabolism, which contains trehalose metabolism. To explore the function of trehalose in DJ3 formation and survival under − 20 °C, a trehalose-6-phosphate synthase encoding gene (Bx-tps), a trehalose-6-phosphate phosphatase encoding gene (Bx-tpp) and 7 trehalase encoding genes (Bx-tres) were identified and investigated. The expression of these 9 genes was related to the formation of DJ3. A treatment under − 20 °C induced the accumulation of trehalose. The survival rate of DJ3 at -20 °C reduced after silencing of any of these trehalose metabolism genes. Further analysis suggested that two trehalose synthesis genes were highly correlated with DJ3 and might be involved in autophagy by regulating with energy conversion related genes. Conclusions The above results indicated that trehalose metabolism promotes DJ3 formation and helps DJ3 survive at -20 °C. Although trehalose accumulation is favorable for DJ3 to cope with low-temperature stress, multiple trehalose metabolism genes need to work together. There may be a multi-path regulated physiological process involving trehalose synthesis genes under low-temperature stress resistance. This physiological process may regulate the formation and maintenance of DJ3 through autophagy and energy conversion.

Esteya vermicola is the first recorded endoparasitic nematophagous fungus with high infectivity capacity, attacking the pinewood nematode Bursaphelenchus xylophilus which causes pine wilt disease. Endosymbionts are found in the cytoplasm of E. vermicola from various geographical areas. We sequenced the genome of endobacteria residing in E. vermicola to discover possible biological functions of these widespread endobacteria. Multilocus phylogenetic analyses showed that the endobacteria form a previously unidentified lineage sister to Phyllobacterium myrsinacearum species. The number of genes in the endobacterium was 4542, with 87.8% of the proteins having a known function. It contained a high proportion of repetitive sequences, as well as more Acyl-CoA synthetase genes and genes encoding the electron transport chain, compared with compared with plant-associated P. zundukense Tri 48 and P. myrsinacearum DSM 5893. Thus, this symbiotic bacterium is likely to be more efficient in regulating gene expression and energy release. Furthermore, the endobacteria in nematophagous fungi Esteya vermicola contained multiple nematicidal subtilase/subtilisin encoding genes, so it is likely that endobacteria cooperate with the host to kill nematodes. [ABSTRACT FROM AUTHOR]

Summary: Pine wilt disease (PWD), caused by the pine wood nematode, Bursaphelenchus xylophilus , is an international quarantine forest disease that damages pine forests over extensive areas and causes massive economic losses. To provide valuable guidelines on screening pesticides against B. xylophilus and the selection of common solvents, we investigated the effects of different concentrations of emamectin benzoate, matrine and four solvents (methanol, ethanol, acetone and dimethyl sulfoxide) on the mortality and locomotor behaviour of B. xylophilus. Emamectin abamectin has nematicidal activity and mitigates locomotor activity of B. xylophilus at a low concentration. The LC50 of emamectin benzoate was 0.0354 mg l−1 at 72 h. Bursaphelenchus xylophilus mortality following exposure to matrine was low; however, nematode locomotor activity decreased by 62.5% following exposure to 500 mg l−1 matrine for 8 h. Additionally, B. xylophilus locomotor activity decreased significantly following exposure to 5 and 10% methanol, ethanol, acetone and dimethyl sulfoxide (DMSO) when compared with that of the water control. Emamectin benzoate and matrine, and high concentrations of four solvents (methanol, ethanol, acetone, and DMSO) inhibit B. xylophilus movement, which, in turn, could affect nematode infectivity. Moreover, low concentrations of non-lethal doses of emamectin benzoate should be considered for application in the control of nematodes, with matrine being an environmentally friendly and potentially nematicidal agent. [ABSTRACT FROM AUTHOR]

Pine wilt disease (PWD), which is caused by the pine wood nematode Bursaphelenchus xylophilus , is among the most serious tree diseases worldwide. PWD is thought to be initiated by sequential excessive hypersensitive responses to B. xylophilus. Previous studies have reported candidate pathogenic molecules inducing hypersensitive responses in pine trees susceptible to B. xylophilus. The functions of some of these molecules have been analyzed in model plants using transient overexpression; however, whether they can induce hypersensitive responses in natural host pines remains unclear due to the lack of a suitable functional analysis method. In this study, we established a novel functional analysis method for susceptible black pine (Pinus thunbergii) seed embryos using transient overexpression by the Apple latent spherical virus vector and investigated five secreted proteins of B. xylophilus causing cell death in tobacco to determine whether they induce hypersensitive responses in pine. We found that three of five molecules induced significantly higher expression in pathogenesis-related genes (p < 0.05), indicating hypersensitive response in pine seed embryos compared with mock and green fluorescence protein controls. This result suggests that tobacco-based screening may detect false positives. This study is the first to analyze the function of pathogenic candidate molecules of B. xylophilus in natural host pines using exogenous gene expression, which is anticipated to be a powerful tool for investigating the PWD mechanism. [ABSTRACT FROM AUTHOR]

Identifying genes/loci for resistance to pine wilt disease (PWD) caused by the pine wood nematode (PWN) is beneficial for improving resistance breeding in Pinus thunbergii, but to date, genetic information using molecular markers has been limited. Here, we constructed a high-density linkage map using genotyping-by-sequencing (GBS) and conducted quantitative trait loci (QTL) analysis for PWD resistance for the self-pollinated progeny of "Namikata 73," which is the most resistant variety among resistant varieties of P. thunbergii, following inoculation tests with PWN. An S1 mapping population consisting of the 116 progenies derived from self-pollination of the resistant variety, "Namikata 73" (resistance rank 5 to PWN), was inoculated with PWN isolate Ka-4 and evaluated for disease symptoms. To construct a high-density linkage map, we used single-nucleotide polymorphisms (SNPs) identified by GBS based on next-generation sequencing technology and some anchor DNA markers, expressed sequence tag (EST)-derived SNP markers and EST-derived simple sequence repeat (SSR) markers, and genomic SSR markers. The linkage map had 13 linkage groups (LGs) consisting of 2,365 markers including 2,243 GBS-SNP markers over a total map distance of 1968.4 centimorgans (cM). Results from QTL analysis using phenotype data and the linkage map indicated that PWD resistance is controlled by a single locus located on LG-3, as identified in a previous study. This locus showed overdominant genetic action in the present study. With the confirmation of PWD1 in two different mapping populations (present study and a previous study), the locus associated with this region is thought to be a good target for marker-assisted selection in P. thunbergii breeding programs in order to obtain high levels of resistance to PWD caused by PWN. [ABSTRACT FROM AUTHOR]

Pine wilt disease (PWD), caused by the pinewood nematode (PWN) Bursaphelenchus xylophilus, is one of the most destructive diseases in trees of the genus Pinus and is responsible for significant environmental and economic losses in North America, Eastern Asia, and Western Europe. However, pine species are not equally affected, with some being tolerant/resistant while others are susceptible to nematode infection for reasons still unclear. The present study aims to investigate differential chemical responses of susceptible and tolerant/resistant pine species shortly after nematode infection by characterizing the phenolic profiles of adult Pinus sylvestris, Pinus pinaster, Pinus pinea, and Pinus halepensis. HPLC and LC-MS were used to identify and quantify the pine´s phenolic compounds: gallic acid, ferulic acid, taxifolin, rutin, resveratrol, (+)-secoisolariciresinol, (−)-epicatechin, protocatechuic acid hexoside, gallic acid hexoside, ferulic acid glucoside, quercetin hexoside, and two unidentified compounds (#A and #B). Prior to infection, we could not differentiate between nematode-tolerant/resistant and susceptible adult pine species based on their constitutive phenolic compounds. In the presence of the PWN, the phenolic profile allowed for a noticeable separation of the PWN-tolerant/resistant P. halepensis from the susceptible P. sylvestris, contrasting with a more homogenous response from P. pinea and P. pinaster. Observations on P. halepensis suggest that taxifolin, resveratrol, and rutin may have an active role in protecting against B. xylophilus, possibly in conjugation with other biochemical and anatomical characters. We emphasize the importance of studying pine tolerant/resistance on adult trees, and not on excised branches, saplings, or seedlings to accurately simulate the nematode–pine host interactions occurring under natural conditions. [ABSTRACT FROM AUTHOR]

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