Search Results (68)

Pinus massoniana Lamb. is an economically important conifer native to China. However, it is highly susceptible to the pine wood nematode (Bursaphelenchus xylophilus, PWN), the causal agent of pine wilt disease (PWD), resulting in substantial ecological and economic losses. To elucidate potential molecular defense mechanisms, 50 NAC (NAM, ATAF1/2, and CUC2) transcription factors (PmNACs) were identified in the P. massoniana genome. Phylogenetic analysis divided these PmNACs into seven subfamilies, and motif analysis identified ten conserved motifs associated with stress responses. Twenty-three genes were selected for expression analysis in various tissues and under exogenous salicylic acid (SA), methyl jasmonate (MeJA), and PWN infection. Six genes (PmNAC1, PmNAC8, PmNAC9, PmNAC17, PmNAC18, and PmNAC20) were significantly up-regulated by both hormonal treatment and PWN infection, implying their involvement in JA/SA-mediated immune pathways. Functional characterization showed PmNAC8 is a nuclear-localized transcription factor with autoactivation activity. Furthermore, transient overexpression of PmNAC8 in Nicotiana benthamiana induced reactive oxygen species (ROS) accumulation and necrotic lesions. Collectively, these results elucidate NAC-mediated defense responses to PWN infection in P. massoniana and identify candidate genes for developing PWD-resistant pine varieties. Full article

Pine wilt disease (PWD), caused by Bursaphelenchus xylophilus Steiner & Buhrer (pine wood nematodes, PWN), impacts forest carbon sequestration and climate change. However, satellite-based PWD monitoring is challenging due to the limited spatial resolution of Sentinel’s MSI sensor, which reduces its sensitivity to subtle biochemical alterations in foliage. We have, therefore, developed a slope product index (SPI) for effective detection of PWD using single-date satellite imagery based on spectral gradients in the visible and near-infrared (VNIR) range. The SPI was compared against 15 widely used vegetation indices and demonstrated superior robustness across diverse test sites. Results show that the SPI is more sensitive to changes in chlorophyll content in the PWD detection, even under potentially confounding conditions such as drought. When integrated into Random Forest (RF) and Back-Propagation Neural Network (BPNN) models, SPI significantly improved classification accuracy, with the multivariate RF model achieving the highest performance and univariate with SPI in BPNN. The generalizability of SPI was validated across test sites in distinct climate zones, including Zhejiang (accuracyZ_Mean = 88.14%) and Shandong (accuracyS_Mean = 78.45%) provinces in China, as well as Portugal. Notably, SPI derived from Sentinel-2 imagery in October enables more accurate and timely PWD detection while reducing field investigation complexity and cost. Full article

Pine wilt disease (PWD), a destructive pine forest disease caused by pine wood nematode (PWN), Bursaphelenchus xylophilus, has led to huge economic losses and ecological environment damage. Thaumatin-like proteins (TLPs) are the products of a complex gene family involved in host defense and a wide range of developmental processes in fungi, plants, and animals. In this study, a tlp gene of B. xylophilus (Bxtlp) (GenBank: OQ863020.1) was amplified via PCR and cloned into the expression vector pET-15b to construct the recombinant vector PET-15b-Bxtlp, which was then transformed into Escherichia coli BL-21(DE3). The recombinant protein was successfully purified using Ni-NTA affinity chromatography. The effect of the Bxtlp gene on the vitality and pathogenicity of PWNs was elucidated through RNA interference (RNAi) and overexpression. Bxtlp dsRNA significantly reduced the feeding, motility, spawning, and reproduction abilities of PWN; shortened its lifespan; and increased the female–male ratio. In contrast, the recombinant BxTLP markedly enhanced the reproductive ability of PWN. In addition, Bxtlp dsRNA increased reactive oxygen species (ROS) content in nematodes, while the recombinant BxTLP was confirmed to have antioxidant capacity in vitro. Furthermore, the bioassays on Pinus thunbergii saplings demonstrated that Bxtlp could significantly influence PWN pathogenicity. Overall, we speculate that Bxtlp affects the pathogenicity of PWNs mainly via regulating ROS levels, the motility, and hatching of PWN. Full article

The pine wood nematode (Bursaphelenchus xylophilus, PWN) is a globally significant quarantine pest that causes severe economic and ecological damage to coniferous forests worldwide. Additionally, PWNs continue to expand into higher latitudes. However, studies on their cold tolerance remain limited. This study investigated the overwintering environment of PWNs in epidemic areas of Liaoning Province, China. It established a protocol to induce anhydrobiosis in PWNs, evaluated their low-temperature resistance, observed morphological changes during anhydrobiosis, and explored potentially involved key genes. The results showed that (1) there was no significant difference in thermal insulation between infected and healthy wood in Liaoning Province; both effectively reduced temperature fluctuation rates, providing a protective function for PWN overwintering. (2) PWNs significantly enabled their cold tolerance through anhydrobiosis, accompanied by significant morphological changes and substantial lipid droplet depletion. (3) Eleven anhydrobiosis-related genes were identified. Among these, the collagen gene family showed consistent expression patterns throughout dehydration and rehydration. This suggests a potential role in cuticle structural changes and osmoregulation during anhydrobiosis. These findings provide a theoretical basis for understanding how PWNs survive winter conditions in high-latitude regions. Additionally, they offer valuable insights for future research into PWN anhydrobiosis and the development of effective control strategies. Full article

Pine wilt disease (PWD), caused by the pine wood nematode (PWN, Bursaphelenchus xylophilus), poses a significant threat to global pine forests and calls for the development of innovative management strategies. Microbial control emerges as an effective, cost-efficient, and environmentally sustainable approach to eliminate the damage from PWD. This review consolidates molecular mechanisms in the microbiological control of PWD, which focus on three core strategies: microbial control activity against PWN, biological control of vector insects, and the enhancement of host tree resistance to nematode infections. The review thoroughly evaluates integrated control strategies in which microbial control is used in traditional management practices. Recent studies have pinpointed promising microbial agents for PWN control, such as nematophagous microorganisms, nematicidal metabolites, parasitic fungi that target vector insects, and microbes that boost plant resistance. In particular, the control potential of volatile organic compounds (VOCs) produced by microorganisms against PWN and the enhancement of pine resistance to PWN by microorganisms were emphasized. Moreover, we assessed the challenges and opportunities associated with the field application of microbiological control agents. We emphasized the feasibility of multi-strategy microbial integrated control, which provides a framework for future studies on microbial-based PWD control strategies. Full article

Pine wilt disease (PWD), caused by the pine wood nematode (PWN, Bursaphelenchus xylophilus), is one of the most serious threats to pine forests worldwide. The fungus Esteya vermicola, with its lunate conidia capable of parasitizing the PWN, has shown promise as an efficient biological control agent against PWD. Solid-state fermentation (SSF) is preferred for large-scale applications in the field, as it facilitates microbial agent transport and ensures a long shelf life. However, research on enhancing the yield of lunate conidia from E. vermicola through SSF is limited. In this study, we initially achieved a yield of 3.04 × 10⁸ conidia/g using a basic SSF medium composed of wheat bran, corn flour, and soybean flour. To improve this yield, we employed an orthogonal experimental design (OED) to identify the optimal medium composition, which required a wheat bran-to-corn flour-to soybean flour ratio of 7:2:1 (w/w/w), a substrate-to-water ratio of 1:0.7 (w/v), and the addition of 1.33% (w/w) glucose, 1.33% (w/w) yeast extract fermentation, and 1.33% (w/w) MgSO₄. Using the response surface methodology (RSM), we calculated the optimal fermentation conditions, which were 24.9 °C, 78.0% relative humidity (RH), an inoculation volume of 16.3% (v/w), and a fermentation time of 7.1 days. Under these conditions, the yield of lunate conidia reached a maximum of 16.58 × 10⁸ conidia/g, a 4.45-fold increase after optimization. This study improved the yield of E. vermicola lunate conidia and provides insights for developing biopesticides based on this strain. Full article

Pine wood nematodes (Bursaphelenchus xylophilus, PWNs) are a major threat to Pinus koraiensis in northeast China, and emamectin benzoate (EB) is commonly used for their control. Although high doses of EB can alleviate symptoms of pine wilt disease (PWD), they do not fully eradicate PWNs due to their detoxification mechanisms. This study investigates the content of EB in P. koraiensis and its efficacy in controlling PWNs after exogenous application of EB. We found that while EB significantly reduced PWN populations, it did not eliminate them. Transcriptomic analysis of PWNs treated with concentration at 20% (LC₂₀) revealed that PWNs exhibit detoxification responses to low EB concentrations (LC₂₀), driven by the Bx-SDR3 gene. RNA interference (RNAi)-mediated silencing of this gene decreased the detoxification ability of PWNs and enhanced the toxic effects of LC₂₀ EB by 20.9%. These results highlight the key role of Bx-SDR3 in PWN detoxification and suggest that targeting this gene could improve the effectiveness of EB, offering a promising strategy for more efficient and eco-friendly pest management. Full article

Among the most concerning threats impacting global forest ecosystems is the pinewood nematode (Bursaphelenchus xylophilus (Steiner and Buhrer, 1934) Nickle, 1970), the causal agent of pine wilt disease. In Europe, effective management of this pest requires comprehensive regulatory and monitoring strategies, including the annual collection of thousands of wood samples from symptomatic trees and their surroundings, inspection of wood packaging materials like pallets, and the trapping of the insect vector, Monochamus spp., through national networks. Insects and wood samples are sent to official laboratories, where the latter are sometimes incubated at 25 °C for 15 days, aiming to maximize the probability of the detection of the nematode. This study expected to elucidate the effect of the wood incubation process on the detection of B. xylophilus by analyzing wood samples from pallets and green wood obtained from pine stands, both harbouring nematodes in adult and juvenile stages. Additionally, the investigation sought to assess how the presence of fungi, which serve as a food source for the nematodes, enables B. xylophilus to persist in treated pallet wood that is colonized by these fungi. The results indicated that the incubation period is unnecessary for detecting B. xylophilus in pallets, except when the wood is heavily colonized by fungi providing suitable nutrition for the nematodes, although such occurrences are expected to be rare. Furthermore, this study found no significant differences in population growth between the two stages of the nematode’s life cycle. This suggests that second-stage juveniles present in wood samples, despite not undergoing sexual differentiation, do not hinder the reproductive capacity of B. xylophilus. The risk of a potential infestation in treated pallet wood is unlikely if the treatment has been performed correctly, and the incubation does not contribute to increasing the probability of detecting the PWN. Conversely, for samples obtained from trees, the incubation period significantly enhances nematode detection. Full article

Chinese forests, particularly the coniferous forest ecosystems represented by pines, play a crucial role in the global carbon cycle, significantly contributing to mitigating climate change, regulating regional climates, and maintaining ecological balance. However, pine wilt disease (PWD), caused by the pine wood nematode (PWN), has become a major threat to forest carbon stocks in China. This study evaluates the impact of PWN invasion on forest carbon stocks in China using multi-source data and an optimized MaxEnt model, and the study analyzes this invasion’s spread trends and potential risk areas. The results show that the high-suitability area for PWN has expanded from 68,000 km² in 2002 to 184,000 km² in 2021, with the spread of PWN accelerating, especially under warm and humid climate conditions and due to human activities. China’s forest carbon stocks increased from 111.34 billion tons of carbon (tC) to 168.05 billion tC, but the carbon risk due to PWN invasion also increased from 87 million tC to 99 million tC, highlighting the ongoing threat to the carbon storage capacity. The study further reveals significant differences in tree species’ sensitivity to PWN, with highly sensitive species such as Masson’s pine and black pine mainly concentrated in the southeastern coastal regions, while less sensitive species such as white pine and larch show stronger resistance in the northern and southwestern areas. This finding highlights the vulnerability of high-sensitivity tree species to PWN, especially in high-risk areas such as Guangdong, Guangxi, and Guizhou, where urgent and effective control measures are needed to reduce carbon stock losses. To address this challenge, the study recommends strengthening monitoring in high-risk areas and proposes specific measures to improve forest management and policy interventions, including promoting cross-regional joint control, enhancing early warning systems, and utilizing biological control measures, while encouraging local governments and communities to actively participate. By strengthening collaboration and implementing control measures, the health and sustainable development of forest ecosystems can be ensured, safeguarding the forests’ important role in climate regulation and carbon sequestration and contributing to global climate change mitigation. Full article

Bursaphelenchus xylophilus (pine wood nematode, PWN) has been present in China for over 40 years and has spread to northeast China, where native pine species are key components of the local top community. Pinus thunbergii is known to be susceptible to PWN among local conifer species, whereas research on PWN’s pathogenicity in Larix remains limited. Furthermore, there are no research reports on PWN infestation in Picea and Abies species within China. This study conducted a detailed analysis of phenotypic changes and temporal spectral reflectance variations in four conifer species in northeast China—P. thunbergii, Larix kaempferi, Picea koraiensis, and Abies holophylla—following artificial inoculation with PWN. The aim of this study is to establish a theoretical basis for identifying the potential hosts and threats of PWN. The study incorporated a 60-day post-inoculation observation period to systematically monitor and compare temporal changes in external morphology, disease susceptibility (incidence and mortality rates), spectral reflectance, and the normalized wilt index (NWI) in 2–3-year-old seedlings of P. thunbergii, L. kaempferi, P. koraiensis, and A. holophylla after inoculation with PWN. The results showed that P. thunbergii displayed the earliest infection symptoms, followed by L. kaempferi, A. holophylla, and finally P. koraiensis. After inoculation, P. thunbergii was the first to experience mortality, followed by L. kaempferi, P. koraiensis, and A. holophylla. Following inoculation, P. thunbergii exhibited the earliest significant increase in NWI (p < 0.001), followed by L. kaempferi and A. holophylla; P. koraiensis showed the latest increase (p < 0.001). In conclusion, the experiment identified P. koraiensis as having the strongest resistance to PWN among the four species, followed by A. holophylla. P. thunbergii showed the weakest resistance, while L. kaempferi exhibited moderate resistance. The ranking of PWN susceptibility for the four conifer species, from highest to lowest, is as follows: P. thunbergii, L. kaempferi, A. holophylla, and P. koraiensis. Full article

Pine wilt disease (PWD) is a devastating disease that occurs worldwide and affects conifers infested by the pine wood nematode (PWN, Bursaphelenchus xylophilus). PWD has caused serious economic and ecological losses in China. The mechanism of disease outbreak is complex, with the associated fungi, specifically ophiostomatoid fungi, thought to play an essential role. However, few ophiostomatoid fungal associates of PWD have been accurately identified. In the present study, we isolated fungi from bark beetles collected from Pinus thunbergii infested by the pine wood nematode on Laoshan Mountain, Shandong province. Three ophiostomatalean fungi were identified and assigned to Graphilbum and Ophiostoma based on phylogenetic analyses and comparison of morphological and cultural features, namely Gra. laoshanense sp. nov., Gra. translucens, and O. ips. This study increases the understanding of the diversity of ophiostomatoid fungi associated with PWD and provides resources for parsing this complex disease. Full article

Pine wilt disease (PWD), which poses a significant risk to pine plantations across the globe, is caused by the pathogenic agent Bursaphelenchus xylophilus, also referred to as the pine wood nematode (PWN). A droplet digital PCR (ddPCR) assay was developed for the quick identification of the PWN in order to improve detection sensitivity. The research findings indicate that the ddPCR assay demonstrated significantly higher analysis sensitivity and detection sensitivity in comparison to traditional quantitative PCR (qPCR). However, it had a more limited dynamic range. High specificity was shown by both the ddPCR and qPCR techniques in the diagnosis of the PWN. Assessments of reproducibility revealed that ddPCR had lower coefficients of variation at every template concentration. Inhibition tests showed that ddPCR was less susceptible to inhibitors. There was a strong linear association between standard template measurements obtained using ddPCR and qPCR (Pearson correlation = 0.9317; p < 0.001). Likewise, there was strong agreement (Pearson correlation = 0.9348; p < 0.001) between ddPCR and qPCR measurements in the evaluation of pine wood samples. Additionally, wood samples from symptomatic (100% versus 86.67%) and asymptomatic (31.43% versus 2.9%) pine trees were diagnosed with greater detection rates using ddPCR. This study’s conclusions highlight the advantages of the ddPCR assay over qPCR for the quantitative detection of the PWN. This method has a lot of potential for ecological research on PWD and use in quarantines. Full article

The pinewood nematode (PWN), Bursaphelenchus xylophilus, is the causal agent of pine wilt disease and is considered an A2 quarantine organism by the European Plant Protection Organisation. In Europe, this nematode has been reported in Pinus pinaster, P. radiata, and P. nigra. In May 2024, severe wilting symptoms were observed in P. sylvestris trees at Serra da Lousã (Coimbra, the central area of continental Portugal). Wood samples were collected from six wilted trees, and the presence of PWN was investigated. From these, B. xylophilus specimens were detected in five out of the six trees. Species identification was performed based on species-specific morphological diagnostic characters, and this was confirmed by real-time PCR using species-specific primers targeting the B. xylophilus satellite DNA region. This study presents the first detection of B. xylophilus in P. sylvestris in Portugal and in Europe. Full article

Pinus, a conifer, dominates the world’s forest ecosystems. But it is seriously infected with pine wood nematode (PWN). Transcription factors (TFs) are key regulators in regulating plant resistance. However, the molecular mechanism of TFs remains thus far unresolved in P. thunbergii inoculated with Bursaphelenchus xylophilus. Here, we used RNA-seq technology to identify differentially expressed TFs in resistant and susceptible pines. The results show that a total of 186 differentially expressed transcription factors (DETFs), including 99 upregulated and 87 downregulated genes were identified. Gene ontology (GO) enrichment showed that the highly enriched differentially expressed TFs were responsible for secondary biosynthetic processes. According to KEGG pathway analysis, the differentially expressed TFs were related to chaperones and folding catalysts, phenylpropanoid biosynthesis, and protein processing in the endoplasmic reticulum. Many TFs such as NAC, LBD, MYB, bHLH, and WRKY were determined to be quite abundant in the DETFs. Moreover, the NAC transcription factor PtNAC9 was upregulated in PWN-resistant and susceptible P. thunbergii and especially distinctly upregulated in resistant pines. By purifying recombinant PtNAC9 protein in vitro, we found that overexpression of PtNAC9 at the early stage of B. xylophilus infection could reduce the degree of disease. We also demonstrated the content of salicylic acid (SA) and the related genes were increased in the PtNAC9 protein-treated plants. These results could be helpful in enhancing our understanding of the resistance mechanism underlying different resistant pine. Full article

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. Full article