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10 pages, 16379 KiB

Open AccessArticle

Three Ophiostomatalean Fungi Associated with Bark Beetles from Pinus thunbergii Infested by Bursaphelenchus xylophilus in Laoshan Mountain (Shandong, China)

by Xiuyue Song, Yingjie Tie, Zheng Wang, Lingguang Kong, Huixiang Liu and Quan Lu

Forests 2024, 15(11), 1990; https://doi.org/10.3390/f15111990 - 11 Nov 2024

Viewed by 397

Abstract

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 [...] Read more.

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

(This article belongs to the Special Issue Advance in Pine Wilt Disease)

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13 pages, 8955 KiB

Open AccessArticle

Tetramycin B₃: An Effective and Biological Nematicide for Bursaphelenchus xylophilus

by Shuaibin Sun, Wenchao Li, Kunyang Ju, Xiong Xiong, Jie Li, Chengming Yu, Yehan Tian and Huixiang Liu

Forests 2024, 15(10), 1699; https://doi.org/10.3390/f15101699 - 26 Sep 2024

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Abstract

Pine wilt disease, caused by Bursaphelenchus xylophilus (Steiner & Buhrer, 1934) Nickle 1981, poses a significant threat to the safety of pine forests in the world. Currently, the available nematicides for controlling this disease are limited. Finding new nematicides is crucial for the [...] Read more.

Pine wilt disease, caused by Bursaphelenchus xylophilus (Steiner & Buhrer, 1934) Nickle 1981, poses a significant threat to the safety of pine forests in the world. Currently, the available nematicides for controlling this disease are limited. Finding new nematicides is crucial for the effective prevention and control of pine wilt disease. In this study, we discovered that tetramycin B₃, derived from Streptomyces ahygroscopicus, demonstrated a promising effect on pine wilt disease. The LC₅₀ values of tetramycin B₃ at 24, 48, and 72 h were 26.49, 23.37, and 12.79 μg/mL, respectively. Tetramycin B₃ significantly inhibited the feeding and growth rate of B. xylophilus at low concentrations while also increasing ROS (reactive oxygen species) production and lipid accumulation. Furthermore, tetramycin B₃ markedly inhibited the activity of detoxifying and protective enzymes. Transcriptome and metabolome analyses indicated that tetramycin B₃ significantly affected the expression of genes related to lysosomes, autophagy, and lipid metabolism in B. xylophilus. Additionally, tetramycin B₃ delayed the onset of pine wilt disease. Transcriptome results showed that tetramycin B₃ significantly influenced the expression of genes related to defense responses in pine trees and induced pine trees to produce disease-resistant mechanisms. Future research will focus on further elucidating the mechanism of action of tetramycin B₃ against B. xylophilus and verifying the gene functions identified through transcriptome screening. Full article

(This article belongs to the Special Issue Advance in Pine Wilt Disease)

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12 pages, 4864 KiB

Open AccessArticle

Characteristics and Conductivity of Emamectin Benzoate-Inclusive Nanocapsule in Pinus massoniana Lamb.

by Na Lin, Xiu Su, Xiang Zhou, Lifeng Zhou, Anliang Chen, Jiafu Hu and Kai Guo

Forests 2024, 15(3), 444; https://doi.org/10.3390/f15030444 - 26 Feb 2024

Cited by 4 | Viewed by 1081

Abstract

To improve the conductivity of nematocidal emamectin benzoate (EB) in pine trees (Pinus massoniana Lamb.), EB-inclusive nanocapsules (EB-NCs) were developed as trunk injections and spraying agents. Microscopy revealed that the EB-NCs were spherical in shape (100–200 nm in diameter) and micro-agglomerated with [...] Read more.

To improve the conductivity of nematocidal emamectin benzoate (EB) in pine trees (Pinus massoniana Lamb.), EB-inclusive nanocapsules (EB-NCs) were developed as trunk injections and spraying agents. Microscopy revealed that the EB-NCs were spherical in shape (100–200 nm in diameter) and micro-agglomerated with an obvious core-shell structure. The EB-NCs formulation maintained high toxicity in Bursaphelenchus xylophilus pine wood nematodes (LC₅₀ = 0.44 mg L⁻¹). Moreover, the formulation had better EB slow-release and photostability. In addition, the EB-NCs formulation was effectively absorbed and transported in the pine trees via either trunk injection or spraying. In terms of trunk injection, the average residues of EB in the lower, middle, and upper branches of P. massoniana 30 days after application in summer were 8.11, 16.42, and 6.98 mg L⁻¹. In terms of spraying treatment, the EB-NC formulation was successfully conducted from the cortical tissue to the cambium and the EB fluorescence intensity inside of the branches was better than that of the 2% EB micro-emulsion. The EB-NC formulation has suitable conductivity in pine trees; hence, this study provides a potential agent for the control of pine wilt disease in the field under all weather conditions. Full article

(This article belongs to the Special Issue Advance in Pine Wilt Disease)

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10 pages, 2717 KiB

Open AccessArticle

Effects of Bacillus cereus NJSZ-13 on Fatty Acid Metabolism of Bursaphelenchus xylophilus

by Min Pan, Jialin Xu, Shengjie Han, Yufeng Sun and Jiajin Tan

Forests 2023, 14(10), 2065; https://doi.org/10.3390/f14102065 - 16 Oct 2023

Viewed by 1004

Abstract

In order to explore the changes in the fatty acid metabolism of Bursaphelenchus xylophilus under the treatment of Bacillus cereus NJSZ-13, the surface changes in lipid droplets were observed under a Zeiss microscope after the B. xylophilus was stained with modified Oil Red [...] Read more.

In order to explore the changes in the fatty acid metabolism of Bursaphelenchus xylophilus under the treatment of Bacillus cereus NJSZ-13, the surface changes in lipid droplets were observed under a Zeiss microscope after the B. xylophilus was stained with modified Oil Red O. The triglyceride (TG) content in B. xylophilus was determined according to the TG kit instructions. The type and content of fatty acids in B. xylophilus were detected by gas chromatography–mass spectrometry (GC-MS); the stearyl coenzyme A of B. xylophilus was analyzed by real-time fluorescence quantitative PCR. The change in Bx-SCD (gene regulating stearyl CoA desaturase in B. xylophilus) expression was observed. The results showed that the lipid droplets of B. xylophilus treated with NJSZ-13 were broken to varying degrees, and the TGs in B. xylophilus decreased continuously. The total fatty acid content in the bodies of treated B. xylophilus decreased: the difference between the fermentation broth treatment and the control was extremely significant (p < 0.01); that between the fermentation filtrate and the control was significant (p < 0.05); and that between the bacterial suspension and the control was not significant (p > 0.05). Saturated fatty acids decreased in all treatments, but not significantly. Compared with the control group, the unsaturated fatty acid content in fermentation broth and fermentation filtrate treatments was extremely significantly reduced, and the unsaturated fatty acid content of the bacterial suspension group was significantly decreased, which indicated that NJSZ-13 mainly caused a decrease in the unsaturated fatty acids in B. xylophilus. The trend in changes in monounsaturated fatty acids and unsaturated fatty acids was the same, but for polyunsaturated fatty acids, the fermentation broth and fermentation filtrate treatments caused a significant decrease in content, but the bacterial suspension resulted in no significant change. The results showed that NJSZ-13 mainly caused a decrease in monounsaturated fatty acid content in B. xylophilus. In addition, the contents of C16:1, C18:1, and C18:2 fatty acids were significantly decreased after treatment with strain NJSZ-13 for 48 h, and the contents of C16:1, C18:1, C18:2, and C20:4 were extremely significantly decreased after the fermentation broth and filtrate treatments. The expression of Bx-SCD in B. xylophilus was significantly lower than that of the control (p < 0.0001). This study analyzed the changes in the content of related substances and relative gene expression in fatty acid metabolism of B. xylophilus treated with strain NJSZ-13, and preliminarily reveals the nematicidal mechanism of strain NJSZ-13 against B. xylophilus. This provides a theoretical basis for further exploration of the key cause of death induced by this strain in B. xylophilus. Full article

(This article belongs to the Special Issue Advance in Pine Wilt Disease)

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18 pages, 7473 KiB

Open AccessArticle

Responses of Plant Species Diversity and Biomass to Forest Management Practices after Pine Wilt Disease

by Jinliang Liu, Weiyong Liu, Jianbin Wu, Boliang Wei, Jing Guo, Lei Zhong and Mingjian Yu

Forests 2023, 14(8), 1636; https://doi.org/10.3390/f14081636 - 14 Aug 2023

Viewed by 1331

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Advance in Pine Wilt Disease)

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11 pages, 2176 KiB

Open AccessArticle

Early Diagnosis of Pine Wood Nematode Disease Based on Chlorophyll Fluorescence Parameters and Organic Acids

by Luyang Shen, Xiaoyu Lin, Fei Liu, Yingzhen Huang, Jianren Ye and Jiajin Tan

Forests 2023, 14(8), 1582; https://doi.org/10.3390/f14081582 - 3 Aug 2023

Cited by 1 | Viewed by 1468

Abstract

Pine wood nematode disease is a destructive disease to the ecological environment and forest resources. The disease is produced by Bursaphelenchus xylophilus, and the onset rate is extremely fast and the pathogenesis of the disease is not clear. Prevention of this disease [...] Read more.

Pine wood nematode disease is a destructive disease to the ecological environment and forest resources. The disease is produced by Bursaphelenchus xylophilus, and the onset rate is extremely fast and the pathogenesis of the disease is not clear. Prevention of this disease is still important in production, so it is of great significance to explore its early diagnosis. In this study, the changes of chlorophyll fluorescence dynamic induction parameters, non-photochemical quenching parameters and organic acid content in needles of 7-year-old-infected Pinus hwangshanensis were studied by chlorophyll fluorescence technology and organic acid mass combined technology. The results showed that in the chlorophyll fluorescence dynamic induction group, Fm/Fo, Fv/Fo, Fm, Psi_o and Pi_Abs showed a significant downward trend, while Phi_Do, ABS/RC, TRO/RC and DIO/RC showed a significant uptrend. In non-photochemical quenching, Fm showed a downward trend, while Qp_L1, Qp_L2, QY_L1, QY_L2 and QY_Lss showed a significant upward trend. In the change of organic acid content, ferulic acid, syringic acid, gallic acid and jasmonic acid showed a significant increasing trend, while benzoic acid and salicylic acid showed a first increasing trend and then decreasing trend. Experimental results show that pine wood nematode had significant effects on photosynthesis and the organic acid content of pine before it showed symptoms of the disease. After comprehensive analysis, chlorophyll fluorescence dynamic induction parameters Pi_Abs, Fm, Phi_Do, TRO/RC, Psi_o, non-photochemical quenching parameters QY_L2, Qp_L1, QY_Lss, QY_L1 and organic acids ferulic acid, syringic acid, benzoic acid and gallic acid contents are ideal indicators for early diagnosis of pine wood nematodiasis. Full article

(This article belongs to the Special Issue Advance in Pine Wilt Disease)

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11 pages, 5363 KiB

Open AccessArticle

Cloning, Bioinformatics Analysis and Physiological Function of the Pine Wood Nematode Bxadh2 Gene

by Luyang Shen, Jiafeng Hu, Yangxue Chen, Jiajin Tan and Jianren Ye

Forests 2023, 14(7), 1283; https://doi.org/10.3390/f14071283 - 21 Jun 2023

Cited by 1 | Viewed by 1590

Abstract

In previous research, the pine wood nematode Bxadh2 gene significantly increased its expression in pine seedlings inoculated with endophytic Bacillus cereus GD2 and pine wood nematode. To explore pine wood nematode Bxadh2 gene function, we cloned and analyzed its biological information, and we [...] Read more.

In previous research, the pine wood nematode Bxadh2 gene significantly increased its expression in pine seedlings inoculated with endophytic Bacillus cereus GD2 and pine wood nematode. To explore pine wood nematode Bxadh2 gene function, we cloned and analyzed its biological information, and we preliminarily studied its physiological function through RNA interference. We found that the Bxadh2 gene’s full CDS length is 1269 bp, which encodes 422 amino acids, and presents a relatively stable hydrophobic protein. The protein encoded by the Bxadh2 gene has no signal peptide or transmembrane structure, and it is an intracellular protein that does not participate in transmembrane movement. The RNAi interference results showed that when the pine wood nematode’s Bxadh2 gene was suppressed, its survival rate and fecundity significantly decreased, indicating that the expression of the Bxadh2 gene was related to the growth and development of pine wood nematodes. Full article

(This article belongs to the Special Issue Advance in Pine Wilt Disease)

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14 pages, 4384 KiB

Open AccessArticle

Screen of Pinus massoniana for Resistance to Pinewood Nematode: In Vitro Propagation and Evaluation of Regenerated Microshoots

by Jia-Yi Guo, Zi-Hui Zhu, You-Mei Chen and Li-Hua Zhu

Forests 2023, 14(5), 1056; https://doi.org/10.3390/f14051056 - 21 May 2023

Viewed by 2129

Abstract

To accelerate breeding of Pinus massoniana Lamb. resistance to pine wilt disease (PWD), caused by the pinewood nematode (PWN), Bursaphelenchus xylophilus, a protocol was established for the in vitro propagation of P. massoniana and the evaluation of resistance of regenerated microshoots from [...] Read more.

To accelerate breeding of Pinus massoniana Lamb. resistance to pine wilt disease (PWD), caused by the pinewood nematode (PWN), Bursaphelenchus xylophilus, a protocol was established for the in vitro propagation of P. massoniana and the evaluation of resistance of regenerated microshoots from different clones to PWN. Axillary bud induction was achieved by culturing cotyledonary node explants from 3-week-old seedlings in Gupta and Durzan (DCR) medium that was supplemented with 4 mg L⁻¹ 6-benzyladenine (BA) and 0.2 mg L⁻¹ α-naphthaleneacetic acid (NAA). Explants with induced buds were transferred to DCR medium without a plant growth regulator to facilitate elongation. Stem segments from elongated shoots were used as propagules for further shoot multiplication. Six-month-old regenerated shoots that met the requirements for a nematode resistance test were inoculated with aseptic PWN (500 PWNs/shoot). The wilting rate varied between clones from 20% to 100%, 18 days after inoculation. Except for Clone 227, which showed the highest resistance with a wilting rate of 0%, other clones showed wilting to various degrees 30 d after inoculation. The number of nematodes that were recovered from Clone 227 was significantly lower than from other clones. This study promotes the resistance breeding of P. massoniana to pine wilt disease and provides an effective method to study the host/pathogen interaction between PWN and P. massoniana. Full article

(This article belongs to the Special Issue Advance in Pine Wilt Disease)

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