Molecular phylogeny, diagnostics, and diversity of plant-parasitic nematodes of the genusHemicycliophora(Nematoda: Hemicycliophoridae)

Abstract

The genus Hemicycliophora (Nematoda: Hemicycliophoridae) contains 132 valid species of plant‐parasitic nematodes, collectively known as ‘sheath nematodes’. Hemicycliophora spp. are characterized morphologically by a long stylet with rounded basal knobs and a cuticular sheath, present in juvenile and adult stages. Populations of 20 valid and 14 putative species of Hemicycliophora and Loofia from several countries were characterized morphologically using light (LM) and scanning electron microscopy (SEM) and molecularly using the D2‐D3 segments of 28S rRNA and internal transcribed spacer (ITS) rRNA gene sequences. LM and SEM observations provided new details on the morphology of these species. PCR‐restriction fragment length polymorphisms (PCR‐RFLPs) of the D2‐D3 of 28S rDNA were proposed for identification of the species. Phylogenetic relationships within populations of 36 species of the genus Hemicycliophora using 102 D2‐D3 of 28S rDNA and 97 ITS rRNA gene sequences as inferred from Bayesian analysis are reconstructed and discussed. Ancestral state reconstructions of diagnostic characters (body and stylet length, number of body annuli, shape of vulval lip and tail), using maximum parsimony and Bayesian inference, revealed that none of the traits are individually reliable characters for classifying the studied sheath nematode. The Shimodaira–Hasegawa test rejected the validity of the genus Loofia. This is the most complete phylogenetic analysis of Hemicycliophora species conducted so far. © 2014 The Linnean Society of London

An 18S rDNA Perspective on the Classification of Criconematoidea

“…However, similarities between the membranous scales of Bakernema and the sheath in Hemicycliophora, and SEM face views that feature a prominent oral disc with proportionally large amphid apertures surrounded by a smooth, continuous annulus, suggest that homologous features may be revealed with an in-depth morphological analysis (Fig. 4;and Subbotin et al, 2014 for SEM images of Hemicycliophora species). Within this near-full length 18S analysis, Criconemoides informis (Micoletzky, 1922) Taylor, 1936 serves as a representative of a second species group in the genus Criconemoides.…”

Morphological and molecular characterisation of two new Hemicycliophora species (Tylenchida: Hemicycliophoridae) with a revision of the taxonomic status of some known species and a phylogeny of the genus

“…Species delimitation of Hemicycliophora was performed using an integrated approach that considered morphological and morphometric evaluation combined with molecular criteria based on phylogenetic inference and sequence analyses as in the previous study (Subbotin et al, 2014).…”

“…The newly obtained sequences of the D2-D3 of 28S rRNA gene, the ITS rRNA gene and the COI gene were aligned using ClustalX 1.83 (Thompson et al, 1997) with default parameters, with corresponding pub- botin et al, 2005Van den Berg et al, 2010;Cordero López et al, 2013;Powers et al, 2014;Ma & Agudelo, 2015;Zeng et al, 2015). Outgroup taxa for each dataset were chosen as shown in the previous study (Subbotin et al, 2014). Three alignments were generated: i) D2-D3 of 28S rRNA gene sequence alignment; ii) ITS rRNA gene sequence alignment; and iii) COI gene sequence alignment.…”

“…Several Hemi-timely identification of these plant-parasitic nematodes is a prerequisite for the selection of effective control management strategies . Recently, a comprehensive study with characterisations of 20 known and 14 putative species, using morphology, nuclear ribosomal RNA gene sequences and PCR-ITS-RFLP profiles, has provided a molecular guide for identification of this nematode group (Subbotin et al, 2014).…”

“…The main aim of the present study was to characterise sheath nematodes from the new and previous collections. In this manuscript we provide: i) descriptions of two new species that were partly characterised in our previous study (Subbotin et al, 2014); ii) a revision of the taxonomic status and morphological descriptions of some known species; iii) testing of the DNA barcoding approach with partial COI mtDNA gene sequences for identification; iv) molecular characterisation of some newly obtained populations of Hemicycliophora using sequences of the D2-D3 expansion segments of 28S rRNA, ITS of the rRNA, and COI genes; and v) a study of phylogenetic relationships within Hemicycliophora species using rRNA and COI gene sequences.…”