scholarly journals Insights into the Role of Fungi in Pine Wilt Disease

2021 ◽  
Vol 7 (9) ◽  
pp. 780
Author(s):  
Cláudia S. L. Vicente ◽  
Miguel Soares ◽  
Jorge M. S. Faria ◽  
Ana P. Ramos ◽  
Maria L. Inácio

Pine wilt disease (PWD) is a complex disease that severely affects the biodiversity and economy of Eurasian coniferous forests. Three factors are described as the main elements of the disease: the pinewood nematode (PWN) Bursaphelenchus xylophilus, the insect-vector Monochamus spp., and the host tree, mainly Pinus spp. Nonetheless, other microbial interactors have also been considered. The study of mycoflora in PWD dates back the late seventies. Culturomic studies have revealed diverse fungal communities associated with all PWD key players, composed frequently of saprophytic fungi (i.e., Aspergillus, Fusarium, Trichoderma) but also of necrotrophic pathogens associated with bark beetles, such as ophiostomatoid or blue-stain fungi. In particular, the ophiostomatoid fungi often recovered from wilted pine trees or insect pupal chambers/tunnels, are considered crucial for nematode multiplication and distribution in the host tree. Naturally occurring mycoflora, reported as possible biocontrol agents of the nematode, are also discussed in this review. This review discloses the contrasting effects of fungal communities in PWD and highlights promising fungal species as sources of PWD biocontrol in the framework of sustainable pest management actions.

2019 ◽  
Vol 49 (6) ◽  
pp. e12564
Author(s):  
Marta Salgueiro Alves ◽  
Anabela Pereira ◽  
Cláudia Vicente ◽  
Manuel Mota ◽  
Isabel Henriques

2020 ◽  
Author(s):  
Yajie Guo ◽  
Qiannan Lin ◽  
lvyi Chen ◽  
Carballar-Lejarazú Rebeca ◽  
Aishan Zhang ◽  
...  

Abstract Background: Monochamus alternatus Hope is one of the insect vectors of pinewood nematode (Bursaphelenchus xylophilus), which causes the destructive pine wilt disease. The microorganisms within the ecosystem, comprising plants, their environment, and insect vectors, form complex networks. This study presents a systematic analysis of the bacterial microbiota in the M. alternatus midgut and its habitat niche.Methods: Total DNA was extracted from 20 types of samples (with three replicates each) from M. alternatus and various tissues of healthy and infected P. massoniana (pines). 16S rDNA amplicon sequencing was conducted to determine the composition and diversity of the bacterial microbiota in each sample. Moreover, the relative abundances of bacteria in the midgut of M. alternatus larvae were verified by counting the colony-forming units.Results: Pinewood nematode infection increased the microbial diversity in pines. Bradyrhizobium, Burkholderia, Dyella, Mycobacterium, and Mucilaginibacter were the dominant bacterial genera in the soil and infected pines. These results indicate that the bacterial community in infected pines may be associated with the soil microbiota. Interestingly, the abundance of the genus Gryllotalpicola was highest in the bark of infected pines. The genus Cellulomonas was not found in the midgut of M. alternatus, but it peaked in the phloem of infected pines, followed by the phloem of heathy pines. Moreover, the genus Serratia was not only present in the habitat niche, but it was also enriched in the M. alternatus midgut. The colony-forming unit assays showed that the relative abundance of Serratia sp. peaked in the midgut of instar II larvae (81%).Conclusions: Overall, the results indicate that the bacterial microbiota in the soil and in infected pines are correlated. The Gryllotalpicola sp. and Cellulomonas sp. are potential microbial markers of pine wilt disease. Additionally, Serratia sp. could be an ideal agent for expressing insecticidal protein in the insect midgut by genetic engineering, which represents a new use of microbes to control M. alternatus.


Plant Disease ◽  
2013 ◽  
Vol 97 (8) ◽  
pp. 1126-1126 ◽  
Author(s):  
H. Y. Wu ◽  
Q. Q. Tan ◽  
S. X. Jiang

The pinewood nematode (PWN) Bursaphelenchus xylophilus (Steiner & Buhrer 1934) Nickle 1970 is the causal agent of pine wilt disease. It is especially damaging in East Asian countries, including Japan, China, and Korea. In China, the nematode has been found in Anhui, Guangdoung, Guizhou, Chongqing, and Zhejiang Provinces since its discovery in Jiangsu Province in 1982 (1). China is confronted with an enormous threat to its pine forests. B. xylophilus is transmitted by the insect vector pine sawyer beetle (Monochamus alternatus). The main host trees are Pinus massoniana, P. thunbergii, and P. densiflora, which are the most common pine trees in China. Shandong Province, located north of Jiangsu Province, is a high-risk area because it was thought to be the northernmost suitable area for the pine wood nematode. P. tabulaeformis, P. densiflora, and P. thunbergii are the principal hosts. In 2010, a pine tree with suspected wilt disease was found in Lushang Forest (36°16′31.11″ N, 118°03′59.79″ E) of P. thunbergii located in Zibo city of Shandong Province. Symptoms were systemic, with almost all leaves brown or yellowish; the tree was nearly dead. Wood samples were collected and nematodes were extracted using a modified Baermann's funnel method. After 12 h, the nematodes were collected from the wood chips, and their morphology was observed with an inverted light microscope (Nikon 90i, Japan). Nematodes had a typical Aphelenchoid-type esophagus and female vulva flap. Females had subcylindrical tails, usually with broadly rounded terminus, some with a short mucro, and flat vulva, whereas males had large paired arcuate spicules with a sharply pointed prominent rostrum, and typical disc-like expansions on distal ends. Standard measurements of these nematodes were as follows: 25 females: body length = 960.9 ± 117.4 (791.5 to 1,265.2) μm, a = 32.1 ± 5.1 (23.7 to 44.5), b = 13.6 ± 1.4 (11.4 to 16.1), c = 28.3 ± 4.6 (21.7 to 42.2), V = 77.8 ± 2.0 (74.2 to 83.9), stylet length = 13.7 ± 1.6 (11.4 to 17.6) μm; 21 males: body length = 785.6 ± 103.2 (609.6 to 1,004.5) μm, a = 33.3 ± 4.4 (26.0 to 40.8), b = 11.9 ± 1.3 (9.0 to 14.6), c = 31.0 ± 2.7 (25.5 to 37.1), stylet length = 13.5 ± 1.9 (11.0 to 17.5) μm, spicule length = 18.8 ± 2.5 (14.9 to 23.9) μm. The morphometrics of this population, apart from body length and “a” value, which are shorter than the Portugal isolate measured by Mota et al. (3), are very much in the same range reported for B. xylophilus. For a more accurate identification, DNA was extracted from individual nematodes using a liquid nitrogen method. The internal transcribed spacers (ITS-1, ITS-2, 5.8S) were amplified by using PCR (2). Nucleotide sequences were compared with the sequences of B. xylophilus in GenBank, accession nos. JN684828 (Portugal), JN684829 (Portugal), JF826219 (Madeira Island) and JQ288086 (Japan). The ITS DNA sequences of the nematode from P. thunbergii were 99% identical to those of B. xylophilus in GenBank. A sequence of this nematode was submitted to the GenBank database and assigned the number KC460340. We have thus confirmed that B. xylophilus is now present north of Changjiang River in Zibo city, Shandong Province. This range expansion, perhaps the result of global warming, will affect both domestic and international quarantine efforts to control the further spread of pinewood nematode. References: (1) X. Y. Cheng et al. Heredity 100:356, 2008. (2) K. Metge and W. Burgermeister. J. Plant Dis. Protect. 113:275, 2006. (3) M. Mota et al. Nematology 1:727, 1999.


2020 ◽  
Author(s):  
Yajie Guo ◽  
Qiannan Lin ◽  
lvyi Chen ◽  
Carballar-Lejarazú Rebeca ◽  
Aishan Zhang ◽  
...  

Abstract Background Monochamus alternatus Hope is one of the insect vectors of pinewood nematode ( Bursaphelenchus xylophilus ), which causes the destructive pine wilt disease. The microorganisms within the ecosystem, comprising plants, their environment, and insect vectors, form complex networks. This study presents a systematic analysis of the bacterial microbiota in the M. alternatus midgut and its habitat niche. Methods Total DNA was extracted from 20 types of samples (with three replicates each) from M. alternatus and various tissues of healthy and infected P. massoniana (pines). 16S rDNA amplicon sequencing was conducted to determine the composition and diversity of the bacterial microbiota in each sample. Moreover, the relative abundances of bacteria in the midgut of M. alternatus larvae were verified by counting the colony-forming units. Results Pinewood nematode infection increased the microbial diversity in pines. Bradyrhizobium , Burkholderia , Dyella , Mycobacterium , and Mucilaginibacter were the dominant bacterial genera in the soil and infected pines. These results indicate that the bacterial community in infected pines may be associated with the soil microbiota. Interestingly, the abundance of the genus Gryllotalpicola was highest in the bark of infected pines. The genus Cellulomonas was not found in the midgut of M. alternatus , but it peaked in the phloem of infected pines, followed by the phloem of heathy pines. Moreover, the genus Serratia was not only present in the habitat niche, but it was also enriched in the M. alternatus midgut. The colony-forming unit assays showed that the relative abundance of Serratia sp. peaked in the midgut of instar II larvae (81%). Conclusions Overall, the results indicate that the bacterial microbiota in the soil and in infected pines are correlated. The Gryllotalpicola sp. and Cellulomonas sp. are potential microbial markers of pine wilt disease. Additionally, Serratia sp. could be an ideal agent for expressing insecticidal protein in the insect midgut by genetic engineering, which represents a new use of microbes to control M. alternatus .


Forests ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 731
Author(s):  
Zhuoqing Hao ◽  
Jixia Huang ◽  
Yantao Zhou ◽  
Guofei Fang

The Yangtze River Basin is among the river basins with the strongest strategic support and developmental power in China. As an invasive species, the pinewood nematode (PWN) Bursaphelenchus xylophilus has introduced a serious obstacle to the high-quality development of the economic and ecological synchronization of the Yangtze River Basin. This study analyses the occurrence and spread of pine wilt disease (PWD) with the aim of effectively managing and controlling the spread of PWD in the Yangtze River Basin. In this study, statistical data of PWD-affected areas in the Yangtze River Basin are used to analyse the occurrence and spread of PWD in the study area using spatiotemporal visualization analysis and spatiotemporal scanning statistics technology. From 2000 to 2018, PWD in the study area showed an “increasing-decreasing-increasing” trend, and PWD increased explosively in 2018. The spatial spread of PWD showed a “jumping propagation-multi-point outbreak-point to surface spread” pattern, moving west along the river. Important clusters were concentrated in the Jiangsu-Zhejiang area from 2000 to 2015, forming a cluster including Jiangsu and Zhejiang. Then, from 2015–2018, important clusters were concentrated in Chongqing. According to the spatiotemporal scanning results, PWD showed high aggregation in the four regions of Zhejiang, Chongqing, Hubei, and Jiangxi from 2000 to 2018. In the future, management systems for the prevention and treatment of PWD, including ecological restoration programs, will require more attention.


2021 ◽  
Vol 12 ◽  
Author(s):  
Honglong Chu ◽  
Haihua Wang ◽  
Yanan Zhang ◽  
Zhumei Li ◽  
Chunyan Wang ◽  
...  

Pine wilt disease (PWD) is a deadly disease to pines (Pinus spp.) worldwide. The occurrence of PWD can reduce the relative abundance of root ectomycorrhizal fungi (ECMF) and dark septate endophytes (DSE). However, the effects of exogenous ECMF/DSE inoculation on the rhizosphere microbial community structure of Pinus tabulaeformis infected by pine wood nematode (PWN) is little known. Here, we tested how ECMF/DSE may improve resistance to PWD by quantifying microbial carbon biomass and soil enzymatic activity among different treatments at 6 and 9 months after PWN infection. Denaturing gradient gel electrophoresis (DGGE) was used to study the microbial community structure at 3, 6, and 9 months after PWN infection in the rhizosphere of P. tabulaeformis seedlings inoculated with ECMF/DSE. The results showed that exogenous ECMF/DSE inoculation reduced the disease severity caused by PWN infection. After PWN infection, the rhizosphere microbial carbon of seedlings inoculated with Amanita vaginata, Suillus bovinus, Gaeumannomyces cylindrosporus, and Paraphoma chrysanthemicola was 38.16, 49.67, 42.11, and 96.05% higher than that of the control group, respectively. Inoculation of ECMF/DSE inhibited the decrease of rhizosphere microbial biomass caused by PWN infection. The richness and diversity of P. tabulaeformis rhizosphere fungi at 9 months were reduced by PWN infection but partially recovered by the exogenous fungi (ECMF/DSE) inoculation except for P. chrysanthemicola, which indicates a role of ECMF/DSE in maintaining stability of the microbial community. Inoculation with ECMF/DSE increased the beneficial bacterial (Thauera sp., Mesorhizobium sp., etc.) and fungal groups (Tomentella ellisii, Wilcoxina mikolae, etc.) of in the rhizosphere. In summary, exogenous ECMF/DSE inoculation could increase P. tabulaeformis resistance to PWD probably by improving the rhizosphere microenvironment.


2016 ◽  
Vol 404 (1-2) ◽  
pp. 237-249 ◽  
Author(s):  
Honglong Chu ◽  
Chunyan Wang ◽  
Haihua Wang ◽  
Hui Chen ◽  
Ming Tang

2019 ◽  
Vol 49 (4) ◽  
pp. e12518 ◽  
Author(s):  
Rimi Yamaguchi ◽  
Koji Matsunaga ◽  
Tomonori Hirao ◽  
Miho Tamura ◽  
Atsushi Watanabe

Insects ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 376 ◽  
Author(s):  
Hongjian Chen ◽  
Dejun Hao ◽  
Zhiqiang Wei ◽  
Lujie Wang ◽  
Tao Lin

Monochamus alternatus is an important insect pest in pine forests of southern China and the dispersing vector of the pine wood nematode, Bursaphelenchus xylophilus, which leads to pine wilt disease (PWD). Microbiome of M. alternatus may contribute to survival of larvae in the host pine trees. In order to investigate the intestinal bacterial structure of M. alternatus during the larvae and pupae stages in host trees, and infer the function of symbiotic bacteria, we used 16S rRNA gene Illumina sequencing to obtain and compare the bacterial community composition in the foregut, midgut, and hindgut of larvae, pupal intestines, larval galleries, and pupal chambers of M. alternatus. The diversity of the bacterial community in larval intestines and pupal intestines were similar, as well as was significantly greater in larval galleries and pupal chambers. Although there were differences in bacterial compositions in different samples, similar components were also found. Proteobacteria and Firmicutes were the two most dominant phyla in all samples, and genera Enterobacter, Raoultella, Serratia, Lactococcus, and Pseudomonas were dominant in both the intestinal samples and plant tissue samples. Enterobacter was the most abundant genus in larval intestines, and Serratia was dominant in pupal intestine. The functions of these dominant and specific bacteria were also predicted through metagenomic analyses. These bacteria may help M. alternatus degrade cellulose and pinene. The specific role of symbiotic bacteria in the infection cycle of PWD also warrants further study in the future.


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