38 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”

    Characterizing the pine wilt disease pathosystem in the Front Range region of Colorado

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    2020 Spring.Includes bibliographical references.Pine wilt disease, caused by the pinewood nematode (Bursaphelenchus xylophilus; PWN), is one of the most damaging invasive species in Asia. Tree mortality associated with PWN has recently been reported in Colorado and surrounding states. There remains little documentation on PWN incidence in native pine species or the biology of potential vectors in the Rocky Mountain region. Here we regionally surveyed for PWN in host trees and two putative insect vectors (Monochamus clamator & M. scutellatus) for two years to develop vector flight phenology models and test the hypothesis that disturbance factors predict vector abundance across the landscape. Flight phenology was similar between vectors: flight initiated in mid-July and continued into October for both species. PWN was distributed throughout the Front Range at rates lower than those reported in the putative native range (Host: 3.6%; Vector 4.2%). Infection rate in hosts varied among sites (0-89%), and four 'epicenters' of vector infectivity were identified. We also report the first incidence of PWN-M. clamator association in the U.S. The four identified epicenter sites varied in the timing of anomalous infection frequency, and flight phenology of infective vectors differed between epicenter and peripheral sites. Monochamus populations were found primarily in natural forest areas and seasonally migrate in small numbers to urban areas. Landscape factors such as proximity to burned area were positively correlated with Monochamus abundance. Synthesis and applications: Our study describes PWN infection frequency to be greater than that expected of a newly introduced pathogen, but lesser than the eastern United States and Canada where PWN is known to be established. Our findings provide tools that can predict exposure windows of disease exposure, which were observed to be highest in the early season in Colorado. We also describe the threat that populations of PWN in wildland forests pose to urban landscapes, and how this risk varies seasonally. These findings collectively serve characterize PWN distribution in the native ecosystem and provide tools that can be used by decision-makers and managers to proactively manage the spread of pine wilt disease

    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

    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

    マツノザイセンチュウ分散型誘導メカニズムの生理学的・分子生物学的解析

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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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    Control biológico del vector del nematodo de la madera del pino Monochamus galloprovincialis Olivier mediante autoinfección con el hongo entomopatógeno Beauveria pseudobassiana S.A. Rehner & Humber

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    Bursaphelenchus xylophilus, cuyo vector es Monochamus galloprovincialis, provoca la enfermedad del marchitamiento del pino. Las estrategias de control se centran en el manejo del vector. Se desarrolla un método de autodiseminación de Beuaveria pseudobassiana, hongo entomopatógeno con elevada mortalidad, que permita la infección sobre el vector, consistente en un sistema de autoliberación, adaptado para autoinfección, de los insectos vectores capturados en el bote colector de las trampas multiembudos. Se intenta reducir las capturas de especies de xilófagos no objetivo mediante modificaciones en el sistema. Se determina la dosis del hongo entomopatógeno que autoinfecte y pueda transmitir inóculo, mediante distintos dispositivos. El sistema de autoliberación-infección, tubo enroscado externamente al bote colector de las trampas y el de escape de insectos no objetivo, mediante mallas de 6,0 mm de luz han resultado exitosos. Se han determinado las características del dispositivo de infección y la concentración del hongo entomopatógeno que pueden resultar adecuadas.Máster en Ingeniería de Montes2020-01-302020-01-3

    Inventory and review of quantitative models for spread of plant pests for use in pest risk assessment for the EU territory

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    This report considers the prospects for increasing the use of quantitative models for plant pest spread and dispersal in EFSA Plant Health risk assessments. The agreed major aims were to provide an overview of current modelling approaches and their strengths and weaknesses for risk assessment, and to develop and test a system for risk assessors to select appropriate models for application. First, we conducted an extensive literature review, based on protocols developed for systematic reviews. The review located 468 models for plant pest spread and dispersal and these were entered into a searchable and secure Electronic Model Inventory database. A cluster analysis on how these models were formulated allowed us to identify eight distinct major modelling strategies that were differentiated by the types of pests they were used for and the ways in which they were parameterised and analysed. These strategies varied in their strengths and weaknesses, meaning that no single approach was the most useful for all elements of risk assessment. Therefore we developed a Decision Support Scheme (DSS) to guide model selection. The DSS identifies the most appropriate strategies by weighing up the goals of risk assessment and constraints imposed by lack of data or expertise. Searching and filtering the Electronic Model Inventory then allows the assessor to locate specific models within those strategies that can be applied. This DSS was tested in seven case studies covering a range of risk assessment scenarios, pest types and dispersal mechanisms. These demonstrate the effectiveness of the DSS for selecting models that can be applied to contribute to EFSA Plant Health risk assessments. Therefore, quantitative spread and dispersal modelling has potential to improve current risk assessment protocols and contribute to reducing the serious impacts of plant pests in Europe
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