Maurice Moens

Root-knot nematodes

Plant-parasitic nematodes devastate crops worldwide, in turn impacting international trade, social and economic development. Effective control of nematodes is essential for crop protection, and requires an understanding of nematode biology, taxonomy, population dynamics and sampling methods. Providing a broad introduction to nematodes as plant parasites, this book begins by describing nematodes by genera, and builds on this foundation to detail nematode biology and pest management, including biological and chemical control. Chapters are authored by international experts and enhanced by extensive illustrations and focus boxes. Fully updated throughout, this new edition is an essential resource for postgraduate students, extension officers, researchers and crop protection scientists

Meloidogyne species: a diverse group of novel and important plant parasites

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Molecular identification of cyst-forming nematodes (Heteroderidae) from Iran and a phylogeny based on ITS-rDNA sequences

RFLP and sequences of ITS-rDNA of 45 populations of cyst-forming nematodes collected from different parts of Iran were analysed and identified as representatives of 21 species. Eight enzymes generated RFLP for all studied populations. Comparison of RFLP profiles and sequences of the ITS regions with published data confirmed the presence of Heterodera avenae, H. filipjevi, H. glycines, H. hordecalis, H. latipons, H. schachtii and H. trifolii in Iran. RFLP patterns and ITS sequences for H. elachista, H. turcomanica, H. mothi and C. cacti were obtained for the first time in this study. Heterodera humuli, H. goettingiana, H. fici, H. elachista, H. turcomanica and Cactodera cacti are recorded for the first time in Iran. These results correspond with morphological and morphometric identification of the populations. Several populations were not identified at the species level and are attributed to Heterodera sp.; some of these may correspond to new species. Twenty-one new sequences from Iranian cyst-forming nematodes and 36 known sequences were used for the phylogenetic analyses. The cyst-forming nematodes formed several clades corresponding to their morphological features. Heterodera mothi and H. elachista clustered with high support with other Cyperi group species and H. turcomanica formed a moderately to highly supported clade with the Humuli group.

Root-knot nematodes (Meloidogyne spp.) in Europe

In Europe, root-knot nematodes are increasingly important. Out of more than 90 Meloidogyne species currently described, 23 have been found on the continent. In the cooler climates, Meloidogyne hapla , M. naasi , M. chitwoodi and M. fallax are prevalent. Meloidogyne arenaria , M. javanica and M. incognita are the most common species in warmer conditions of southern Europe, but also in glasshouses in northern Europe. Morphological identification of root-knot nematodes is difficult and time consuming; therefore, many research groups have been developing molecular techniques for identification of Meloidogyne species. Meloidogyne chitwoodi and M. fallax are quarantine organisms and subject to regulations, and the highly aggressive M. enterolobii has been added to the EPPO alert list. Differences between temperate and tropical Meloidogyne species and their prevalence in Europe imply the need for different management strategies in south and north Europe. Possible crop rotations for the control of root-knot nematodes are limited due to the wide host range of several important species. The banning of methyl bromide and restrictions on other fumigant pesticides in the EU have increased the application of biofumigation significantly in south Europe. The egg-parasitising fungus Paecilomyces lilacinus is commercialised in Germany and applied as dispersible granules for application in water. Intensive research is conducted on the egg-parasitising fungus Pochonia chlamydosporia , and the obligate parasitic bacterium Pasteuria penetrans. European research has paid much attention to resistance breeding and selection. The Mi gene of tomato is widely used but resistance-breaking populations of M. incognita and M. javanica have been reported in different countries.

Molecular characterisation of 18 Pratylenchus species using rDNA Restriction Fragment Length Polymorphism

The RFLP technique was used to establish a reliable diagnostic method for 18 Pratylenchus species: Pratylenchus agilis, P. bolivianus, P. brachyurus, P. coffeae, P. crenatus, P. fallax, P. goodeyi, P. loosi, P. mediterraneus, P. neglectus, P. penetrans, P. pratensis, P. pseudocoffeae, P. scribneri, P. subranjani, P. thornei, P. vulnus and P. zeae. The polymerase chain reaction (PCR) amplified the ITS regions from all species and populations examined and revealed large differences in length, ranging in size from approximately 900 to 1250 bp. The rDNA fragments were digested with five restriction enzymes (CfoI, DdeI, HindIII, HpaII, and PstI). All Pratylenchus species can be differentiated from each other by a combination of at least two enzymes. CfoI differentiated all nematode species with the exception of P. fallax, P. penetrans and P. pseudocoffeae. P. fallax was further separated by a DdeI restriction, and P. pseudocoffeae by a PstI digestion. Intraspecific RFLP were observed. Upon CfoI, DdeI, HindIII, or HpaII digestion, it was possible to separate the three P. coffeae populations studied from each other. La technique RFLP a ete utilisee pour creer une methode fiable de diagnostic pour 18 especes de Pratylenchus: Pratylenchus agilis, P. bolivianus, P. brachyurus, P. coffeae, P. crenatus, P. fallax, P. goodeyi, P. loosi, P. mediterraneus, P. neglectus, P. penetrans, P. pratensis, P. pseudocoffeae, P. scribneri, P. subranjani, P. thornei, P. vulnus et P. zeae. La reaction de polymerisation en chaine (PCR) a amplifie les regions de l’ITS pour toutes les especes et populations etudiees et a mis en evidence de grandes differences dans la taille des gammes de longueur, de 900 a 1250 bp approximativement. Les fragments de rDNA ont ete digeres a l’aide de cinq enzymes de restriction (CfoI, DdeI, HindIII, HpaII, and PstI). Toutes les especes de Pratylenchus ont pu etre differenciees les unes des autres par une combinaison d’au moins deux enzymes. CfoI a differencie toutes les especes a l’exception de P. fallax, P. penetrans et P. pseudocoffeae. P. fallax a ete ulterieurement separe par une restriction DdeI, et P. pseudocoffeae par une digestion PstI. Des RFLP intraspecifiques ont ete observes. Par les digestions CfoI, DdeI, HindIII, ou HpaII, il s’est revele possible de separer les unes des autres les trois populations etudiees de P. coffeae.

Identification of cyst forming nematodes of the genus Heterodera (Nematoda: Heteroderidae) based on the ribosomal DNA-RFLP

Amplified ITS region products of rDNA from 25 valid species and one unidentified species from the genus Heterodera and from Meloidodera alni were digested by 26 restriction enzymes. A combination of seven enzymes clearly separated the agriculturally most important species from each other and from their sibling species. Species specific digestion profiles of ITS regions and a table with approximate sizes of digested fragments for several identification enzymes are given. Heterogeneity of ITS regions was revealed for some cyst forming nematode species. Des fragments amplifies de la region de l’ITS du rDNA de 25 especes valides et d’une espece non identifiee du genre Heterodera et de Meloidodera alni ont ete soumis a une digestion par 26 enzymes de restriction. La combinaison de sept enzymes a permis une separation nette des especes les plus importantes en agriculture, tant les unes par rapport aux autres que par rapport aux especes jumelles. Sont donnes les profils specifiques de digestion des regions de l’ITS et un tableau regroupant les tailles approximatives des fragments digeres pour plusieurs enzymes d’identification. L’heterogeneite des regions de l’ITS a ete revelee chez quelques especes de nematodes a kyste.

Bursaphelenchus xylophilus: opportunities in comparative genomics and molecular host-parasite interactions.

Most Bursaphelenchus species are fungal feeding nematodes that colonize dead or dying trees. However, Bursaphelenchus xylophilus, the pine wood nematode, is also a pathogen of trees and is the causal agent of pine wilt disease. B. xylophilus is native to North America and here it causes little damage to trees. Where it is introduced to new regions it causes huge damage. The most severely affected areas are found in the Far East but more recently B. xylophilus has been introduced into Portugal and the potential for damage here is also high. As incidence and severity of pine wilt disease are linked to temperature we suggest that climate change is likely to exacerbate the problems caused by B. xylophilus and, in addition, will extend (northwards in Europe) the range in which pine wilt disease can occur. Here we review what is currently known about the interactions of B. xylophilus with its hosts, including recent developments in our understanding of the molecular biology of pathogenicity in the nematode. We also examine the potential developments that could be made by more widespread use of genomics tools to understand interactions between B. xylophilus, bacterial pathogens that have been implicated in disease and host trees.

A molecular phylogenetic approach to Longidoridae (Nematoda: Dorylaimida)

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.

Identification of Heterodera avenae group species by morphometrics and rDNA-RFLPs

Summary ‐Canonical discriminant analysis of four morphometric charactersof juvenilesand restriction enzymes analysis of ribosomal DNA sequences were used to distinguish Heterodera arenaria , H. aucklandica , H. avenae, H. elipjevi, H. hordecalis , H. iri, H. latipons, H. litoralis , H. schachtii and an undescribed species from grasslands. The results of unweighted pair group cluster analysis showed that H. avenae populations formed three groups and H. elipjevi two groups at the 80% level of similarity. Intraspecie c polymorphism was revealed by rDNA-RFLP studies and two types of ITS regions within H. avenae populations can be distinguished. The pattern of restriction bands obtained with BsuRI, PstI and TaqI clearly distinguished populations of H. elipjevifrom other species of the H. avenae group. Further enzymes and their combinations distinguished the other species. There are no enzymes which differentiate European populations of H. avenae from H. arenaria. Morphometrics, restriction endonuclease cleavage maps of ITS regions and a dendrogram of putative phylogenetic relations of several cyst-forming nematode species are given. Resume ‐ Identie cation des espe ces du groupe Heterodera avenae par la morphometrie et les rDNA-RFLP ‐ L’ analyse canonique discriminante sur quatre caracte res morphome triques des juve niles et l’ analyse des enzymes de restriction de l’ ADN ribosomal ont e te utilise es pour identie er Heterodera arenaria , H. aucklandica , H. avenae, H. elipjevi, H. hordecalis , H. iri, H. latipons, H. litoralis , H. schachtii et une nouvelle espe ce originaire de prairies.Lesre sultats de l’ analyse UPGMAont montre que les populations d’H. avenae formaient trois groupes et celles d’H. elipjevi deux groupes a un niveau de similarite de 80%. Le polymorphisme intraspe cie que a e te re ve le par des e tudes de rDNA-RFLP et deux types de re gions de l’ ITS peuvent e tre mis en e vidence dans les populations d’H. avenae. Les mode les de bandes de restriction obtenus avec BsuRI, PstI et TaqI ont identie e clairement les populations d’H. elipjevi des autres espe ces du groupe H. avenae. D’ autres enzymes et leurs combinaisons ont identie e les autres espe ces. Aucun enzyme n’ a diffe rencie les populations europe ennes d’H. avenae de H. arenaria. Les caracte res morphome triques, les cartes de clivage des re gions des ITS par l’ endonucle ase de restriction et un dendogramme des relations phyloge ne tiques suppose es sont donne s.

Molecular and morphological characterisation of the Heterodera avenae species complex (Tylenchida: Heteroderidae)

Species of the Heterodera avenae complex, including populations of H. arenaria, H. aucklandica, H. australis, H. avenae, H. filipjevi, H. mani, H. pratensis and H. ustinovi, obtained from different regions of the world were analysed with PCR-RFLP and sequencing of the ITS-rDNA, RAPD and light microscopy. Phylogenetic relationships between species and populations of the H. avenae complex as inferred from analyses of 70 sequences of the ITS region and of 237 RAPD markers revealed that the cereal cyst nematode H. avenae is a paraphyletic taxon. The taxonomic status of the Australian cereal cyst nematode H. australis based on sequences of the ITS-rDNA and RAPD data is confirmed. Morphometrical and ITS-rDNA sequence analyses revealed that the Chinese cereal cyst nematode is different from other H. avenae populations infecting cereals and is related to H. pratensis. Bidera riparia Kazachenko, 1993 is transferred to the genus Heterodera as H. riparia (Kazachenko, 1993) comb. n. As a consequence, H. riparia Subbotin, Sturhan, Waeyenberge & Moens, 1997 becomes a junior secondary homonym and is renamed as H. ripae nom. nov. Morphological, morphometrical characters and RFLP profiles for identification of the nine species presently placed in the H. avenae species complex are given.