27 research outputs found

    Global occurrence of pine wilt disease: biological interactions and integrated management

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    Plant pathogens cause severe losses in a wide range of crops and forestry plant species worldwide, being a major obstacle toward achieving sustainable agriculture and forestry. In forests, pathogens can affect sustainable management by affecting economic trade and serious ecological losses can occur, such as the ability to store carbon, reduce flood risk or purify water (Boyd et al., 2013). Ranking in the top ten of the most damaging plant-parasitic nematodes worldwide, the migratory endoparasitic nematode Bursaphelenchus xylophilus (pinewood nematode, PWN) is the causal agent of Pine wilt disease (PWD) being responsible for the tremendous decline of conifers species in Eurasian conifer forests”

    Molecular diversity and relationships of fig associated nematodes from South Africa

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    Nematodes of figs and fig wasps have received limited attention in Africa since their discovery in 1973. Sixteen of the 25 species of native South African figs were sampled for nematode associates using molecular barcoding with three loci (SSU, LSU D2-D3 and mtCOI) and fourteen (93%) were positive for at least one nematode species. Thirty-three putative species of nematodes were identified and classified according to the loci that were amplified and successfully sequenced. Fourteen putative nematode species were classified as Aphelenchoididae, of which nine were identified as Ficophagus from four species of Ficus from the section Galoglychia (i.e., five ex F. burkei including one shared with F. natalensis, one ex F. glumosa, one ex F. lutea, and one ex F. stuhlmannii) and one species ex F. sur from the section Sycomorus. In addition, there were four nematode species classified as Schistonchus s.s. from section Galoglychia figs (i.e., one ex F. burkei, two ex F. trichopoda, and one ex F. glumosa). There was also one species of Bursaphelenchus nematode recovered from F. sur from the section Sycomorus. Sixteen putative nematode species were classified as Diplogastridae, of which eight occurred in two clades of what is currently called Parasitodiplogaster with one (P. salicifoliae) being recovered from two Ficus species in the section Urostigma (F. salicifolia and F. ingens) and seven diplogastrids being associated with six species of Ficus from the section Galoglychia (i.e., two ex F. burkei including P. sycophilon, one ex F. stuhlmannii, one ex F. burtt-davyi, one ex F. trichopoda, one ex F. abutilifolia and one ex F. sansibarica). Three Acrostichus spp., a Teratodiplogaster and a Pristionchus species were recovered from F. sur and two Teratodiplogaster spp. and Pristionchus sycomori were recovered from F. sycomorus with both Ficus species belonging to the subgenus and section Sycomorus. The identities of the previously described T. martini and Parasitodiplogaster doliostoma (= Pristionchus sp. 35) are discussed. Lastly, there was a panagrolaimid identified from F. petersii.The National Research Foundation of South Africa and the Japan Society for the Promotion of Science.http://www.plosone.orgpm2022BiochemistryGeneticsMicrobiology and Plant Patholog

    The in vitro cultivation of Bursaphelenchus spp. at the reference laboratory for quarantine pests at Julius Kühn-Institut in Braunschweig

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    Das Forstquarantänelabor des Julius Kühn-Instituts in Braunschweig (Deutschland) kuratiert eine einzigartige Sammlung lebender Bursaphelenchus-Arten, zudem Dauer­präparate und ITS-RFLP Muster dieser Arten. Die Sammlung wurde von Dr. Helen Braasch gegründet und umfasst derzeit 48 Arten in 305 verschiedenen Isolaten. Diese Isolate wurden über 30 Jahre hinweg weltweit aus verschiedenen Habitaten (Bäumen) und anderen Bezugs­quellen, wie Holzimporten einschließlich Holzverpackungsmaterial, gesammelt. Die Aufzucht der Nema­toden auf sporulierenden und nicht sporulierenden Botrytis cinerea – Kulturen ist anspruchsvoll, arbeitsintensiv und erfordert sowohl Erfahrung als auch Geduld.The Forest quarantine laboratory at Julius Kühn-Institut in Braunschweig (Germany) curates a unique collection of living Bursaphelenchus species, permanent slides and ITS-RFLP profiles. The collection was initiated by Dr. Helen Braasch and currently comprises 48 species in 308 different isolates. These isolates were collected over 30 years across the globe from various habitats and sources, like forest trees and wood imports including wooden packaging material. Cultivation of the nematodes on sporulating and non-sporulating Botrytis cinerea is sophisticated, labor-intensive and requires both, experience and patience

    Detection of classic and cryptic Strongyloides genotypes by deep amplicon sequencing: A preliminary survey of dog and human specimens collected from remote Australian communities

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    © 2019 This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication. Strongyloidiasis is caused by the human infective nematodes Strongyloides stercoralis, Strongyloides fuelleborni subsp. fuelleborni and Strongyloides fuelleborni subsp. kellyi. The zoonotic potential of S. stercoralis and the potential role of dogs in the maintenance of strongyloidiasis transmission has been a topic of interest and discussion for many years. In Australia, strongyloidiasis is prevalent in remote socioeconomically disadvantaged communities in the north of the continent. Being an isolated continent that has been separated from other regions for a long geological period, description of diversity of Australian Strongyloides genotypes adds to our understanding of the genetic diversity within the genus. Using PCR and amplicon sequencing (Illumina sequencing technology), we sequenced the Strongyloides SSU rDNA hyper-variable I and hyper-variable IV regions using Strongyloides-specific primers, and a fragment of the mtDNA cox1 gene using primers that are broadly specific for Strongyloides sp. and hookworms. These loci were amplified from DNA extracted from Australian human and dog faeces, and one human sputum sample. Using this approach, we confirm for the first time that potentially zoonotic S. stercoralis populations are present in Australia, suggesting that dogs represent a potential reservoir of human strongyloidiasis in remote Australian communities

    DNA barcoding em Nematoda: uma análise exploratória utilizando sequências de cox1 depositadas em bancos de dados

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    Tradicionalmente, os nematoides (Filo Nematoda) são identificados através de características morfológicas, mas essa abordagem nem sempre é suficiente. Além disso, há uma potencial diversidade críptica no filo muito difícil de ser detectada e descrita. Neste trabalho, avaliamos a eficácia do gene citocromo c oxidase I (cox1) como DNA barcode para nematoides. Através de uma ampla amostragem no banco de dados GenBank e de um rigoroso processo de curadoria, foram obtidas 4.283 sequências de cox1 atribuídas a 516 espécies e 196 gêneros de nematoides. A partir do conjunto de dados principal, adicionalmente compilamos 20 conjuntos de dados secundários, de modo a representar as categorias de subclasse (2), subordem (3), família (8) e gênero (7). Realizamos cálculos de distância interespecífica e intraespecífica para verificar se em alguma escala taxonômica do Filo Nematoda existe um barcoding gap que torne possível a definição de um limiar de distância genética. Adicionalmente, testamos a eficácia do gene cox1 como DNA barcode para a identificação de nematoides e utilizamos o software ABGD (Automatic Barcode Gap Discovery) para estimar o número de espécies presentes no conjunto de dados compilado. Apenas dois dos 21 conjuntos de dados analisados mostraram um barcoding gap consistente (Strongyloides e Strongyloididae), embora exista uma tendência forte ao barcoding gap em pelo menos outros sete conjuntos de dados. Nossos dados mostram que a posição do barcoding gap (ou da tendência a esse gap) varia muito, e que o uso de DNA barcoding em níveis taxonômicos inferiores, como gênero e família, gera resultados mais satisfatórios. Os resultados apontam que o gene cox1 funciona para a identificação de mais de 75% das espécies amostradas, o que sugere que esse marcador é eficiente para identificação de espécimes, embora seja atualmente subutilizado. No entanto, identificações incorretas de sequências do GenBank e problemas na delimitação de espécies dificultam a interpretação dos dados obtidos. Isso é corroborado pelas análises feitas no ABGD, que estimaram um número de espécies diferente que o previsto para a maioria dos conjuntos de dados analisados. Nossos resultados mostram que através da manutenção de um banco de dados de referência que obedeça a critérios taxonômicos rigorosos, o uso do gene cox1 como código de barras molecular pode se tornar um importante aliado dos caracteres morfológicos na taxonomia e sistemática de Nematoda.Traditionally, nematodes (phylum Nematoda) are identified through morphological characteristics, but this approach is not always sufficient. In addition, there is a cryptic nematode diversity that is very difficult to detect and describe. We evaluated the effectiveness of cytochrome c oxidase subunit I (cox1) as a DNA barcoding gene for nematodes. Through extensive sampling in GenBank and a rigorous curation process, 4,283 cox1 sequences were obtained representing 516 species and 196 genera of nematodes. From the main data set, we compiled 20 sets of secondary data to represent the categories of subclass (2), suborder (3), family (8), and genus (7). We performed interspecific and intraspecific comparisons in multiple taxonomic levels of phylum Nematoda to search for a barcoding gap that makes possible the definition of a threshold. In addition, we tested the effectiveness of the cox1 gene as a species identifier for nematodes and used ABGD (Automatic Barcode Gap Discovery) software to estimate the number of putative species present in the compiled datasets. Only two of the 21 datasets analyzed showed a consistent barcoding gap (Strongyloides and Strongyloididae), although there is a strong tendency to a barcoding gap in at least other seven data sets. Our data showed that the position of the barcoding gap (or the tendency to it) greatly varies, and that the use of DNA barcoding at lower taxonomic levels such as genus and family yields more satisfactory results. Our analysis showed that cox1 successfully identifies more than 75% of the species sampled, which suggests that this marker is efficient for specimen identification although it is currently underexplored for this phylum. However, incorrect labeling of GenBank sequences and problems in species delimitation make it difficult to interpret the obtained data. As shown in the ABGD results, for most of the analyzed data sets the number of putative species inferred was different from the taxonomic labels informed on GenBank. Our results show that through the maintenance of a reference database that obeys rigorous taxonomic criteria, cox1 might be an important ally to morphology in nematode taxonomy and systematics


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    学位の種別: 課程博士審査委員会委員 : (主査)東京大学教授 福田 健二, 東京大学教授 富樫 一巳, 東京大学准教授 松下 範久, 東京大学准教授 練 春蘭, 国立研究開発法人森林研究・整備機構森林総合研究所研究員 神崎 菜摘University of Tokyo(東京大学

    Systematic Identification of the Xylophilus Group in the Genus Bursaphelenchus

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    The pine wood nematode (PWN) Bursaphelenchus xylophilus (Steiner & Buhrer, 1934) Nickle, 1970 is the agent responsible for pine wilt disease (PWD). This nematode has been killing native pine trees (Pinus densiflora, P. thunbergii, P. luchuensis) in Japan since the early twentieth century. It is the number one forest pest in Japan and has been spread to China, Korea, Portugal, and Spain. The nematode is native to North America (Canada, USA, Mexico) and is thought to have been carried to Japan at the beginning of the twentieth century on timber exports. Up to now, the genus Bursaphelenchus Fuchs, 1937 comprises nearly 120 species (14 groups). Around 14 species very similar to B. xylophilus are put together and named the xylophilus group. This chapter presents the grouping history, subspecies or genetic types in species of the xylophilus group, and an identification key for 14 species of the xylophilus group, ITS-RFLP identification, and other molecular identification methods are also discussed

    Transmission electron microscopic observation of body cuticle structures of phoretic and parasitic stages of Parasitaphelenchinae nematodes

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    Using transmission electron microscopy, we examined the body cuticle ultrastructures of phoretic and parasitic stages of the parasitaphelenchid nematodes Bursaphelenchus xylophilus, B. conicaudatus, B. luxuriosae, B. rainulfi; an unidentified Bursaphelenchus species, and an unidentified Parasitaphelenchus species. Nematode body cuticles usually consist of three zones, a cortical zone, a median zone, and a basal zone. The phoretic stages of Bursaphelenchus spp., isolated from the tracheal systems of longhorn beetles or the elytra of bark beetles, have a thick and radially striated basal zone. In contrast, the parasitic stage of Parasitaphelenchus sp., isolated from bark beetle hemocoel, has no radial striations in the basal zone. This difference probably reflects the peculiar ecological characteristics of the phoretic stage. A well-developed basal radially striated zone, composed of very closely linked proteins, is the zone closest to the body wall muscle. Therefore, the striation is necessary for the phoretic species to be able to seek, enter, and depart from host/carrier insects, but is not essential for internal parasites in parasitaphelenchid nematodes. Phylogenetic relationships inferred from near-full-length small subunit ribosomal RNA sequences suggest that the cuticle structures of parasitic species have apomorphic characters, e.g., lack of striation in the basal zone, concurrent with the evolution of insect parasitism from a phoretic life history

    Identification, systematics and phylogeny of the genera in the family Aphelenchoididae (Nematoda: Tylenchomorpha)

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    First detection of Bursaphelenchus luxuriosae associated with Pinus pinaster in Portugal, and in Europe

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    During a field survey carried out on symptomatic maritime pine trees (Pinus pinaster) in Góis, central Portugal, Bursaphelenchus luxuriosae was isolated for the first time in Portugal, and in Europe. Identification of the nematodes was based on morphological characters and molecular analyses for this species. The general morphology of both females and males is in agreement with the original description for B. luxuriosae, namely the typical morphology of the male spicules and the conspicuous morphology of female tail. Species identification was confirmed through sequencing of the ITS rDNA region and the fragment spanning the D2/D3 domain of the 28S rDNA gene. This species belongs to the xylophilus-group and is the third species in this group known in Portugal. The nematodes were retrieved in small numbers (<100 nematodes/100 g dry wood), and no insect vector association could be established