Satellite DNA as a target for TaqMan real-time PCR detection of the pinewood nematode, Bursaphelenchus xylophilus

The pinewood nematode (PWN), Bursaphelenchus xylophilus , is a major pathogen of conifers, which impacts on forest health, natural ecosystem stability and international trade. As a consequence, it has been listed as a quarantine organism in Europe. A real-time PCR approach based on TaqMan chemistry was developed to detect this organism. Specific probe and primers were designed based on the sequence of the Msp I satellite DNA family previously characterized in the genome of the nematode. The method proved to be specific in tests with target DNA from PWN isolates from worldwide origin. From a practical point of view, detection limit was 1 pg of target DNA or one individual nematode. In addition, PWN genomic DNA or single individuals were positively detected in mixed samples in which B. xylophilius was associated with the closely related non-pathogenic species B. mucronatus , up to the limit of 0.01% or 1% of the mixture, respectively. The real-time PCR assay was also used in conjunction with a simple DNA extraction method to detect PWN directly in artificially infested wood samples. These results demonstrate the potential of this assay to provide rapid, accurate and sensitive molecular identification of the PWN in relation to pest risk assessment in the field and quarantine regulation

A metagenetic approach to determine the diversity and distribution of cyst nematodes at the level of the country, the field and the individual.

Distinct populations of the potato cyst nematode (PCN) Globodera pallida exist in the UK that differ in their ability to overcome various sources of resistance. An efficient method for distinguishing between populations would enable pathogen-informed cultivar choice in the field. Science and Advice for Scottish Agriculture (SASA) annually undertake national DNA diagnostic tests to determine the presence of PCN in potato seed and ware land by extracting DNA from soil floats. These DNA samples provide a unique resource for monitoring the distribution of PCN and further interrogation of the diversity within species. We identify a region of mitochondrial DNA descriptive of three main groups of G. pallida present in the UK and adopt a metagenetic approach to the sequencing and analysis of all SASA samples simultaneously. Using this approach, we describe the distribution of G. pallida mitotypes across Scotland with field-scale resolution. Most fields contain a single mitotype, one-fifth contain a mix of mitotypes, and less than 3% contain all three mitotypes. Within mixed fields, we were able to quantify the relative abundance of each mitotype across an order of magnitude. Local areas within mixed fields are dominated by certain mitotypes and indicate towards a complex underlying ‘pathoscape’. Finally, we assess mitotype distribution at the level of the individual cyst and provide evidence of ‘hybrids’. This study provides a method for accurate, quantitative and high-throughput typing of up to one thousand fields simultaneously, while revealing novel insights into the national genetic variability of an economically important plant parasite

A pragmatic approach to identifying Aphelenchoides species for plant health quarantine and pest management programmes

SIGLEAvailable from British Library Document Supply Centre- DSC:DXN057982 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

A new record of Tylenchus stachys Brzeski, 1996 (Nematoda:Tylenchidae) from China

A population of Tylenchus stachys found around the roots of Acer sp. from China is described and compared with the original description. Description, measurements and illustrations are provided. This is the first report of T. stachys from China. The population is also compared to T. skarduensis and T. safroni, similar species with areolated lateral fields.Se describe una población de Tylenchus stachys recolectada en la rizosfera de Acer sp. en China, y se compara con la descripción original. Se presentan descripción, medidas e ilustraciones. Ésta es la primera cita de T. stachys en China. La población se compara también con T. skarduensis y T. safroni, especies similares con los campos laterales areolados

An updated list of the plants associated with plant-parasitic Aphelenchoides (Nematoda: Aphelenchoididae) and its implications for plant-parasitism within this genus

Few Aphelenchoides spp. are facultative plant-parasites (foliar and bulb nematodes); three of them are well known in agricultural systems, namely Aphelenchoides besseyi, A. fragariae and A. ritzemabosi. Ten other plant-parasitic species, A. arachidis, A. bicaudatus, A. blastophthorus, A. dalianensis, A. ensete, A. nechaleos, A. paranechaleos, A. saprophilus, A. sphaerocephalus and A. subtenuis, have been reported from a limited number of plant species. We compiled a new database of the associated plants for these thirteen species, a comprehensive list that includes 1104 reports from 126 botanical families. A. besseyi, A. fragariae and A. ritzemabosi represent 94% of the reports, circa 83% and 16% of the total reports correspond to flowering plants and ferns, respectively, with three records on conifers and two from other botanical groups also listed. Most plant-parasitic Aphelenchoides show a remarkably broad diversity of associated plants. Most species appear to have no specific plant hosts (i.e. are generalists). The broad host ranges of these species and absence of more intimate interactions with the associated plants highlights the primitive mode of parasitism in Aphelenchoides species, making them potentially interesting in the study of the evolution of plant parasitism. Even though the compiled list of associated plants is long, it probably only represents a fraction of the potential range. The complete compilation has been uploaded to http://nematodes.myspecies.info/

Current nematode threats to world agriculture

Many genera and species of nematodes attack almost all crops affecting their yield potential. Their distribution, diversity and potential damage depend on many factors including their centres of origin and subsequent spread, the agroecological conditions and the tolerance and resistance of the crops used in that agricultural system. A sustainable approach to the control of plant-parasitic nematodes is to prevent their spread on to clean land. Phytosanitary measures are a major strategy to achieve this aim, and their implementation is part of the regulatory system of each country. A history and description of international plant health legislation is given by Hockland et al. (2006). The interception or detection of listed or unlisted quarantine organisms could result in destruction of a shipment or infected crop, or a banning of growing host plants on infested land. In other cases, suppression of the infestation is considered to be a more practical approach that allows trade to continue. The key nematodes on major world food commodities and their production are discussed in this chapter in addition to the challenges posed by two groups of quarantine nematodes. This information should provide an insight to the problems or potential future problems and the currently known ways to address these