Search

The Longidoridae are a group of ectoparasitic nematodes including two subfamilies and six genera with hundreds of species. Sequences of the D2 and D3 expansion region of the large subunit (LSU) rRNA nuclear gene were amplified and used to reconstruct the phylogeny of longidorids. Phylogenetic analyses with maximum parsimony (MP), maximum likelihood (ML) and Bayesian inference (BI) were performed with one outgroup taxon and 62 longidorid sequences. Confidence of inferred clades was assessed by non-parametric bootstrapping for MP and Bayesian posterior probability for ML. All analyses placed Paralongidorus species as an inner group within the otherwise monophyletic genus Longidorus. The genus Xiphinema, except for X. americanum-group species, was placed as the sister group of Longidorus with strong support from the ML and BI analyses. The X. americanum-group was strongly supported as an exclusive clade to other genus Xiphinema species. The position of the Xiphidorus clade was not well resolved and the phylogenetic analyses did not support it as a sister group to Longidorus as previously inferred from morphology. Secondary structure models were constructed for the D2/D3 region of LSU rRNA for all studied species. It was found that sequence-based and structural morphometric rRNA phylogenies were incongruent. [ABSTRACT FROM AUTHOR]

Isoelectrofocusing of superoxide dismutase (SOD) isoforms was carried out on the extracts of 117 nematode populations belonging to the so-called Xiphinema americanum-group. These populations came from the USA (77), Chile (5), Argentina (1), Venezuela (5), Portugal (15), Italy (2), Crete (1), Montenegro (1), Slovakia (4), Hungary (3), Egypt (1) and India (2). A total of 17 bands of enzyme activity were observed in the screening, whilst single enzyme phenotypes showed from two to eight bands. The high degree of SOD polymorphism of this nematode collection was grouped by cluster analysis into seven distinct homogeneous groups characterised by specific combinations of SOD markers. Sub-groups could be discriminated for larger groups. The small Groups 3 and 5 were constituted mostly by populations from USA east coast states (i.e., NY and PA, respectively). The larger Group 1 resulted from the association of populations coming from various and distant North American States. In other large groups, North American populations were associated with South American and European populations. Overall, the data presented here suggest that geographic separation and different hosts do not seem to be the source of genetic diversity for the X. americanum-group. When an adequate number of populations were collected from the same country, the variability expressed by such a sub-sample was comparable to that of the whole nematode collection. For the first time, homogeneous populations of a large collection of X. americanum-group populations were associated by molecular means in order to explore further approaches that may help resolve the recalcitrant taxonomy and phylogeny of this much debated group. [ABSTRACT FROM AUTHOR]

Trichodorids are plant-ectoparasitic nematodes, causing economically important diseases in many crops. In this study, we characterised ribosomal DNA (rDNA) of four trichodorid species from two different genera (i.e., Paratrichodorus macrostylus, P. pachydermus, Trichodorus primitivus and T. similis). Sequence data from the 18S and 5.8S genes showed high similarity; in contrast, sequence data from the internal transcribed spacer regions (ITS) were highly variable. Sequence divergence between the two genera included many insertions and deletions. Trichodorus primitivus and T. similis ITS regions of 1537 and 1303 bp, respectively, are the longest reported to date in the Phylum Nematoda. Further exploration of the sequence data indicated perfect and non-homologous repeats which were confined to the middle of the ITS regions. [ABSTRACT FROM AUTHOR]

A short insert genomic library for Xiphinema index, the natural vector of Grapevine Fanleaf Virus, was constructed from degenerate oligonucleotide primed PCR (DOP-PCR) products. The genomic library was screened for (CA)[sub n] microsatellites. Screening of 6200 colonies and comparison of the sequencing results revealed seven (CA)[sub n] containing microsatellites, coded here as XIMSL1, XIMSL2, XIMSL3, XIMSL4, XIMSL5, XIMSL6 and XIMSS1. XIMSL prefixed microsatellites were followed by the motif of the same long interspersed element. Microsatellite XIMSS1 has some similarity to the short interspersed element. Except for XIMSL1, all microsatellites were proven to be effective diagnostic tools at species level. Genetic diversity between and within populations was also evaluated for each microsatellite. [ABSTRACT FROM AUTHOR]

The plant-parasitic nematode Paratrichodorus anemones efficiently transmits tobacco rattle virus that causes substantial economic damage to vegetable and ornamental flower-bulb crops. The nematode acquires and transmits virus particles when feeding on plant roots, but previous studies on feeding by trichodorid nematodes suggested that the nematodes destroyed the cells upon which they fed. For successful establishment of virus infection in a plant, virus particles would have to be introduced by the nematode into root cells that would remain fully functional. Consequently, the efficient transmission of the genus Tobravirus by trichodorids could not occur where the majority of attacked root cells become irreversibly damaged and, therefore, unsuitable for establishment of virus infection. Live specimens of P. anemones feeding on Nicotiana tabacum seedlings growing in agar were examined in real time using videoenhanced interference light microscopy to determine how trichodorids acquire and transmit Tobravirus particles. The feeding cycle of P. anemones had four distinct phases: i) root exploration, ii) cell exploration, iii) cell sampling, and iv) cell feeding, followed by a quiescent period. Preceding the initiation of phase iv) an average of four cells, which had been perforated by the nematode onchiostyle, were immediately abandoned and thus remained fully functional. Also, during this phase, about 5% of the perforated cells remained alive and fully functional, providing a suitable environment for the establishment of virus infection. Each feed on a single cell was similar to that previously observed with Trichodorus similis, being in four phases, i.e., cell wall perforation, salivation, ingestion and withdrawal. [ABSTRACT FROM AUTHOR]

When feeding, Xiphinema index induces remarkable cellular modifications at the feeding site in the root tips of its hosts, similar to those induced by root endoparasites such as Meloidogyne spp. The large size of X. index enables direct analysis of their proteins. Following immunisation of a mouse with macerated extracts of X. index bodies, a panel of monoclonal antibodies (MAbs) was obtained against this nematode. The MAbs were used in immunolocalisation studies and antibodies recognising epitopes present at the surface coat, inner cuticle, dorsal gland cell and dorsal duct, body wall muscle fibres, nervous system and reproductive system were identified. These antibodies provide useful tools for studying plant-nematode interactions. [ABSTRACT FROM AUTHOR]

Plant-parasitic nematodes are small and extremely difficult to identify. Previous studies have demonstrated the potential for lectin- or antibody-assisted identification of nematodes. We present an extension of this technology, using antibody- or lectin-coated magnetic beads (Dynabeads) to recover target nematodes from mixtures of specimens. Lectins and antisera that bound specifically and reproducibly to the whole surface of second stage juveniles of Globodera rostochiensis and Meloidogyne arenaria were identified. These were then used as probes bound to Dynabeads to recover nematodes from test suspensions. While both types of probe isolated nematodes from suspension, antibody-coated beads recovered them more efficiently than beads coated with lectins. Other factors that affected the efficiency of recovery, such as the age of the nematode samples, were analysed. This study revealed that Dynabeads coated with a probe of suitable specificity could be used to extract nematodes from mixtures of species. This technology may ultimately be useful in 'non-expert systems' for routine detection and quantification of nematode species. [ABSTRACT FROM AUTHOR]

Examination of the fine structure of the body cuticle of Trichodorus cylindricus , T. nanjingensis, T. pakistanensis , T. primitivus, Paratrichodorus anemones , P.hispanus , P.minor , P.pachydermus , P.porosus and P.teres revealed three distinct types, each characterised by differences in layers 4 to 6. A new description is provided for layer 5 and the presence of intracuticular canals and hemidesmosomes as types of anchoring structures for the epidermis are discussed. [ABSTRACT FROM AUTHOR]

The effects of a) systemic virus infection (arabis mosaic and tomato black ring nepoviruses), b) ectoparasitic nematode feeding (Xiphinema diversicaudatum and Longidorus elongatus) and c) a combination of virus infection and nematode feeding on the natural abundances of [sup 13]C(delta[sup 13]C) and [sup 15]N(delta[sup 15]N) of nitrogen-starved Petunia hybrida were studied. Pathogen-induced effects were not confined to sites of virus infection or nematode feeding. Those treatments with nematodes feeding on Petunia hosts and those with a combination of virus infection and nematode feeding resulted in a depletion of shoot and root [sup 15]N compared with controls. Virus-infected plants were more [sup 15]N-enriched than those fed upon by nematodes which, in turn, were more [sup 15]N-enriched than those with both nematode and virus in combination. Shoot delta[sup 13]C values from infected treatments were not significantly different from controls. Although root delta[sup 13]C was significantly different from controls in most treatments, absolute differences were small. Differences in delta[sup 15]N between infected and control plants were probably caused by physiological responses to pathogen infection/feeding such as production of PR-proteins and/or release of nitric oxide. Le contenu naturel en [sup 15]N et [sup 13]C comme indicateur de la reaction de Petunia hybrida a l'infestation par les nematodes Longidorides et les nepovirus - La presente etude a porte sur l'influence i) d'une infection virale systemique (nepovirus de la mosaique Arabis et du cercle noir de la tomate), ii) d'une atteinte par des nematodes ectoparasites (Xiphinema diversicaudatum et Longidorus elongatus) et iii) d'une combinaison de deux types de pathogenes sur le contenu naturel en [sup 13]C(delta[sup 13]C) et en [sup 15]N(delta[sup 15]N) de Petunia hybrida deficients en azote. Les effets induits par ces organismes pathogenes ne sont pas limites aux sites de l'infection virale ou a ceux des attaques des nematodes. Compares aux temoins, les traitements comportant les seules attaques de nematodes et ceux comportant des attaques combinees des deux types de parasites provoquent une diminution du [sup 15]N des racines et des parties aeriennes. Les plants infectes par les virus avaient un taux en [sup 15]N plus eleve que ceux attaques par les nematodes, lesquels, en revanche, contenaient plus de [sup 15]N que les plants soumis simultanement aux deux types de parasites. Les taux de delta[sup 13]C dans les parties aeriennes des plants soumis aux differentes attaques n'etaient pas significativement differents de ceux des temoins. Si, dans la plupart des traitements, les taux de delta[sup 13]C dans les racines etaient significativement differents de ceux des temoins, ces differences restaient faibles en valeur absolue. Les differences dans les taux en delta[sup 15]N entre plants infectes et temoins sont probablement la resultante de reactions physiologiques aux pathogenes, telles la production de proteines PR ou l'emission d'oxyde nitrique. [ABSTRACT FROM AUTHOR]