First report of Hemicriconemoides litchi associated with Piper sarmentosum and revision of the genus Hemicriconemoides in Vietnam

The taxonomic status of Hemicriconemoides litchi, H. mangiferae, and H. strictathecatus has been in debates for many years. In this study, a population of H. litchi collected from the rhizosphere of Piper sarmentosum is characterized using a combination of morphology and molecular data. Our results are in agreement with other authors to maintain the validity of H. litchi and provide sequences of H. litchi with correct names on GenBank. A revision on the genus Hemicriconemoides in Vietnam is also discussed.

First report with morphometrics and molecular characterization of phtyonematodes associating mango trees in the tropics of Saudi Arabia

A sum of 218 composite rhizosphere soil samples were collected from around the feeder roots of mango, Mangifera indica growing in Jazan region, the tropical south west corner of Saudi Arabia. Samples were rendered for nematodes extraction using the centrifugal floatation method, and the stylet-bearing nematodes were morphologically identified according to the standardized taxonomical keys. A list of 14 stylet-bearing nematode genera and/or species were found to be associating the roots of mango in this study. Species identification of the most important parasitic nematodes, in this list, was carried-out, based on morphometrics and morphological features. Identification of these species was then molecularly confirmed using the D3 expansion region of 28S ribosomal RNA (rRNA) gene. These nematodes included; Tylenchorhynchus mediterraneus, Hoplolaimus seinhorsti, Hemicriconemoides strictathecatus, Longidorus latocephalus and Xiphinema elongatum. Some new local nematode-host records in Saudi Arabia were recorded including; Aphelenchus sp., H. strictathecatus, L. latocephalus, and T. mediterraneus. Some new world nematode-host records were also reported including; L. latocephalus and T. mediterraneus.

Characterisation of two Chinese native Hemicriconemoides species (Nematoda: Criconematidae) with updated descriptions of H. chitwoodi Esser, 1960 and Criconemoides myungsugae Choi & Geraert, 1975

Populations of Hemicriconemoides chitwoodi, H. fujianensis, H. parasinensis, and Criconemoides myungsugae isolated in China from the rhizosphere soil of woody perennials were characterised molecularly, important morphological details being elucidated by SEM observations. The morphometric data of the Chinese populations were compared with all previously reported populations. The SEM observations of en face views indicated that H. chitwoodi and H. parasinensis have lip patterns belonging to type 1 and phylogenetically both species clustered with other Hemicriconemoides species that showed the same kind of lip pattern. On the other hand, H. fujianensis showed a lip pattern belonging to type 2 and phylogenetically appears basal to the above-mentioned clade. SEM observation of C. myungsugae showed that the first lip annulus forms a non-projecting uninterrupted disc and the labial annulus is a rectangular shape with slight dorsal and ventral indentations. Phylogenetic relationships among Criconemoides spp. are apparently not well resolved. The present study provides updated morphological descriptions, molecular diagnostics and phylogenetic relationships of H. chitwoodi, H. fujianensis, H. parasinensis, and C. myungsugae, the last species being the first report from China.

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

Hemicycliophora presently contains 132 valid species of sheath nematodes. Within several samples obtained from surveys in Canada, South Africa, Spain and the USA, we distinguished six valid and six putative unidentified species by integrating the results of morphological and molecular analyses. Valid species included: H. californica, H. gracilis, H. parvana, H. poranga, H. raskii, and H. signata. The putative unidentified species were indicated as Hemicycliophora sp. 10, sp. 12, sp. 15, sp. 16, sp. 17, and sp. 18. Two new species of sheath nematodes from Spain and the USA were described and named as H. onubensis sp. n. and H. robbinsi sp. n., respectively. Hemicycliophora wyei is proposed as a junior synonym of H. parvana and H. ripa is proposed as a junior synonym of H. poranga. Eighteen valid and 13 unidentified species of sheath nematodes were characterised using the partial COI mtDNA gene. A total of 94 new sequences of which 77 were for the COI mtDNA gene were obtained in this study. Phylogenetic relationships within Hemicycliophora, using the D2-D3 expansion segments of 28S rDNA, ITS rRNA and COI gene sequences, are presented as inferred from Bayesian analysis.

DNA barcoding, phylogeny and phylogeography of the cyst nematode species of the Avenae group from the genus Heterodera (Tylenchida: Heteroderidae)

Among the recognised species groups of Heterodera, the Avenae group is one of the largest with a total of 12 species. Ten of them, H. arenaria, H. aucklandica, H. australis, H. avenae, H. filipjevi, H. mani, H. pratensis, H. riparia, H. sturhani and H. ustinovi, are morphologically closely related and represent the H. avenae species complex, and the other two, H. hordecalis and H. latipons, are morphologically more distinct from this complex. In this study we provide comprehensive phylogenetic analyses of several hundred COI and ITS rRNA gene sequences from the Avenae group using Bayesian inference, maximum likelihood and statistical parsimony. Some 220 COI and 11 ITS rRNA new gene sequences from 147 nematode populations collected in 26 countries were obtained in this study. Our study showed that the COI gene is a powerful DNA barcoding marker for identification of populations and species from the Avenae group. A putatively new cyst nematode species related to H. latipons was revealed from the analysis of COI and ITS rRNA gene datasets. COI gene sequences allow distinguishing H. arenaria, H. australis and H. sturhani from each other and other species. Problems of species delimiting of these species are discussed. The results of the analysis showed that COI haplotypes corresponded to certain pathotypes of the cereal cyst nematodes. It is recommended that information on COI haplotypes of studied populations be included in research with these nematodes. Based on the results of phylogeographical analysis and age estimation of clades with a molecular clock approach, it was hypothesised that several species of the Avenae group primarily originated and diversified in the Irano-Anatolian hotspot during the Pleistocene and Holocene periods and then dispersed from this region across the world. Different geographic barriers, centres and times of origin might explain current known distribution patterns for species of the Avenae group. Possible pathways, including a long distance trans-Atlantic dispersal, and secondary centres of diversification are proposed and discussed.

Morphological and molecular characterisation of Hemicriconemoides paracamelliae sp. n. (Nematoda: Criconematidae) and two known species of Hemicriconemoides from China

Sheathoid nematodes of the genus Hemicriconemoides are migratory root-ectoparasites of many crops but damage is documented for only a few species. Hemicriconemoides paracamelliae sp. n., isolated in Hangzhou, Zhejiang, China, from the rhizosphere of Cinninghamia lanceolata, is described together with H. kanayaensis and H. parataiwanensis. These three species are characterised morphologically and molecularly with important morphological details elucidated by SEM photographs. The new species can be characterised by the en face view having a dorsoventrally orientated oral disc with slit-like opening, and the labial plate being composed of two lateral semi-globular shaped projections on the lateral sides of the oral disc. This new species has the first lip annulus expanded and slightly wider than the second, stylet 83 (80-85) μm long, excretory pore located 5-6 annuli posterior to the base of the pharyngeal bulb, vulva slit-like, vulval flaps absent, spermatheca rounded to oblong-shaped, and anus located 5-8 annuli posterior to vulva. The tail is elongated, conoid, with the terminal annuli curving dorsally or ventrally to form a finely rounded tip. The study provides the first record of H. kanayaensis from mainland China, a new host association of H. parataiwanensis, and molecular sequencing data of the 18S, 28S D2-D3 and ITS sequences.