Taxonomy of the genus Doryllium Cobb, 1920 (Nematoda: Dorylaimida) with description of two new and a known species.

Two new and a known species of the genus Doryllium Cobb, 1920 are described and illustrated. Doryllium enigmatum n. sp. is characterized by a body length of 0.40-0.52 mm; continuous lip region; rounded lips; asymmetrical odontostyle, 5-6 µm long, and flanged odontophore 9-11 µm in length; pharynx with slender anterior part which expands into a slightly constricted pyriform basal bulb, occupying about 16-18% of total neck length; mono-opisthodelphic female genital system; 7-9 µm long anterior uterine sac; transverse vulva and rounded-hemispheroid tail. Doryllium asymmetricum n. sp. is characterized by its 0.52-0.63 mm long body; cap-like, slightly offset lip region; asymmetrical odontostyle, 6 µm in length and 9-11 µm long odontophore with weak flanges; pharynx with slender anterior part which expands gradually into pear-shaped basal bulb, occupying about 16.4-18.5% of total neck length; mono-opisthodelphic female genital system; anterior uterine sac 17-30 µm in length, filled with sperms; transverse vulva and rounded-hemispheroid tail. D. minor is redescribed based on specimens collected from several localities in India and Germany. The diagnosis of the genus Doryllium is emended and a valid list of species with their synonymies and a diagnostic compendium of all the known species is provided.

A new species of the rare nematode genus Margollus Pena-Santiago, Peralta & Siddiqi, 1993 (Nematoda: Tylencholaimoidea) from Turkey.

Margollus turcicus sp. n., is described and illustrated from vineyard soil in Turkey. The new species is characterized by having a medium sized body (L=1.0-1.2 mm); cuticle with distinct striations; radial refractive elements abundant; lip region distinctly narrower than the adjoining body and slightly offset from the body contour by a depression; cephalic and labial papillae not discernible; strong labial and post-labial sclerotization present; amphids well developed with sclerotized walls; stylet 27-28.5 microm long, odontophore distinctly flanged, 0.3 times the odontostyle length; pharyngeal bulb offset by constriction, 33-37 microm long; mono-opisthodelphic female genital system with anterior branch 22-41 microm long; spicules 49 microm long; single weak ventromedian supplement and short hemispheroid tail in both sexes.

Application of the secondary structure model of rRNA for phylogeny: D2-D3 expansion segments of the LSU gene of plant-parasitic nematodes from the family Hoplolaimidae Filipjev, 1934.

Knowledge of rRNA structure is increasingly important to assist phylogenetic analysis through reconstructing optimal alignment, utilizing molecule features as an additional source of data and refining appropriate models of evolution of the molecule. We describe a procedure of optimization for alignment and a new coding method for nucleotide sequence data using secondary structure models of the D2 and D3 expansion fragments of the LSU-rRNA gene reconstructed for fifteen nematode species of the agriculturally important and diverse family Hoplolaimidae, order Tylenchida. Using secondary structure information we converted the original sequence data into twenty-eight symbol codes and submitted the transformed data to maximum parsimony analysis. We also applied the original sequence data set for Bayesian inference. This used the doublet model with sixteen states of nucleotide doublets for the stem region and the standard model of DNA substitution with four nucleotide states for loops and bulges. By this approach, we demonstrate that using structural information for phylogenetic analyses led to trees with lower resolved relationships between clades and likely eliminated some artefactual support for misinterpreted relationships, such as paraphyly of Helicotylenchus or Rotylenchus. This study as well as future phylogenetic analyses is herein supported by the development of an on-line database, NEMrRNA, for rRNA molecules in a structural format for nematodes. We also have developed a new computer program, RNAstat, for calculation of nucleotide statistics designed and proposed for phylogenetic studies.

Occurrence, hosts, morphology, and molecular characterisation of Pasteuria bacteria parasitic in nematodes of the family Plectidae.

Parasitic bacteria of the genus Pasteuria are reported for three Anaplectus and four identified and several unidentified Plectus species found in eight countries in various habitats. The pasteurias from plectids agree in essential morphological characters of sporangia and endospores as well as in developmental cycle with those of the Pasteuria species and strains described from tylenchid nematodes, but appear to be mainly distinguished from these by absence of a distinct perisporium in the spores and the endospores obviously not being cup- or saucer-shaped. The wide range of measurements and morphological peculiarities of sporangia and endospores suggest that probably several Pasteuria species have to be distinguished as parasites in Plectidae. From an infected juvenile of an unidentified plectid species the 16S rRNA gene sequence of Pasteuria sp. was obtained. Substantial sequence divergence from described Pasteuria species and its phylogenetic position on molecular trees indicate that this Pasteuria sp. could be considered as a new species. Preliminary results of the analysis of DNA phylogeny of Pasteuria spp. and their nematode hosts provide evidence for incongruence of their phylogenetic history and of host switching events during evolution of the bacterial parasites.

Molecular Diagnostics, Taxonomy, and Phylogeny of the Stem Nematode Ditylenchus dipsaci Species Complex Based on the Sequences of the Internal Transcribed Spacer-rDNA.

ABSTRACT The stem nematode Ditylenchus dipsaci is of great economic importance worldwide as a parasite of agricultural crops and horticultural plants. The internal transcribed spacer (ITS) of rDNA from 23 populations of the D. dipsaci complex from various host plants were amplified and sequenced. Seven previously studied populations were also included in the study. The phylogenetic analysis of the full ITS and ITS2 sequence alignments using minimum evolution, maximum parsimony, and Bayesian inference under the complex model of DNA evolution revealed trees with two main clades: (i) D. dipsaci sensu stricto with diploid chromosome numbers and comprising most isolates from agricultural, ornamental, and several wild plants, and (ii) Ditylenchus spp. with polyploid chromosome numbers, reproductively isolated from diploid populations, and subdivided into six subclades ("giant race" from Vicia faba, Ditylenchus species parasitizing various Asteraceae, and a Ditylenchus sp. from Plantago maritima). Using the energy minimization approach and comparative sequence analysis, it has been found that the secondary structure of ditylenchid ITS2 is organized in three main domains. The importance of knowledge on the RNA structure for phylogenetic analysis is discussed. Conventional polymerase chain reaction (PCR) and real-time PCR with SYBR green dye I with a species specific primer have been developed for detection and quantification of D. dipsaci sensu stricto Validation tests revealed a rather high correlation between real numbers of fourth-stage juveniles of the stem nematodes in a sample and expected numbers detected by real-time PCR. Problems of accuracy of quantification are discussed.