New Records of Ditylenchus Species from Southern Alberta, Canada

The presence of plant-parasitic nematodes (PPNs) in cultivated areas is a limiting factor in achieving marketable crop yield. To control and alleviate the effects of these nematodes and determine appropriate management strategies, species-level identification is crucial. Therefore, we conducted a nematode diversity survey, which resulted in the detection of four Ditylenchus species in cultivated areas of southern Alberta, Canada. The recovered species had six lines in the lateral field, delicate stylets (>10 µm long), distinct postvulval uterine sacs, and pointed to rounded tail tips. The morphological and molecular characterization of these nematodes revealed their identity as D. anchilisposomus, D. clarus, D. tenuidens and D. valveus, all of which are members of the D. triformis group. All of the identified species were found to be new records in Canada except for D. valveus. Accurate Ditylenchus species identification is crucial because false-positive identification can result in the implementation of quarantine measures over the detected area. Our current study not only documented the presence of Ditylenchus species from southern Alberta, but also described their morpho-molecular characteristics and subsequent phylogenetic relationships with related species. The results of our study will aid in the decision on whether these species should become a part of nematode management programs since nontarget species can become pests due to changes in cropping patterns or climate.

First report of Xiphinema ifacolum Luc, 1961 (Dorylaimida: Longidoridae) from Nigeria

A population of a species of dagger nematode (Xiphinema) belonging to the non-americanum group was recovered from the fields of kola nut (Cola sp.) in southern Nigeria. The morphological and morphometric data obtained from this population were consistent with the characteristics of the species Xiphinema ifacolum. In addition, molecular identification based on D2-D3 expansion segments of 28S rRNA and partial mitochondrial COI gene regions confirmed its identity. According to our knowledge, this is the first report of the species from Nigeria, and the second report from Africa, after the original description from Foulaya, Guinea.

Description of Laimaphelenchus piceae sp. n., a new evidence of cryptic speciation, and L. sinensis Gu et al., 2020 (Rhabditida: Aphelenchoididae), a record from Shanxi province, north China

This contribution deals with the record and description of one new species and record of one known species of the genus Laimaphelenchus from Shanxi province, north China. The type population of L. piceae sp. n. is characterised by having females 642-807 μm long, the cephalic region with six labial sectors divided by ribs, stylet 12-14 μm long, lateral field with four incisures, postvulval uterine sac (PUS) 114-161 μm long, vulva with a well-developed anterior flap, tail with a single stalk at tip, bearing four pedunculate tubercles, each tubercle including 5-7 finger-like protrusions; males spicules 18-24 μm long and three pairs of caudal papillae present. The new species looks closely similar to L. persicus, representing its cryptic species, being separated by differences in some morphological indices and partial large subunit (LSU) rDNA sequences. Its morphological differences from other relevant species were discussed. L. sinensis was also recorded from Shanxi province for the first time. The phylogenetic relationships of the recovered populations were reconstructed using sequences of the near full length small subunit (SSU) and D2-D3 segments of LSU rDNA, and the relationships of both species were discussed.

Data of an Iranian Population of L. proximus Sturhan & Argo, 1983, with taxonomic revision of L. israelensis Peneva, Orion, Shlevin, Bar-Eyal & Brown, 1998 (Nematoda: Longidoridae) and Proposal for a New Synonymy

The morphology and morphometric characteristics of a Longidorus population recovered from a wheat-potato field in Hamadan province, western Iran, fit well with those given for two species, L. proximus and L. israelensis. The Iranian population was characterized by 5.6 to 8.6-mm-long females having a 17 to 21-µm-wide lip region separated from the rest of the body by a shallow depression, pocket-shaped amphidial fovea with a simple base and a ventral enlargement, a guiding ring at 31 to 40 µm distance from the anterior end, 108 to 127-µm-long odontostyle, 58 to 64-µm-long odontophore, 101 to 129-µm-long pharyngeal bulb with remarkably larger dorsal gland nucleus (at 49 to 53% of the bulb length) and two smaller ventrosublateral nuclei (at 66 to 76% of the pharyngeal bulb length), four juvenile developmental stages, and a rare male. The morphological and molecular data corroborated its assignment to the species L. proximus. In molecular phylogenetic analyses using partial LSU rDNA D2-D3 sequences, the presently studied Iranian population and previously sequenced isolates of L. proximus formed a clade with L. cretensis, L. iranicus, L. pseudoelongatus, and L. closelongatus, all except L. pseudoelongatus with no available data, having the similar pharyngeal gland nuclei size and arrangement. In internal transcribed spacer 1 (ITS1) phylogeny, it formed a clade with L. sturhani and four aforementioned species. The characters delimiting the two species L. proximus and L. israelensis were discussed and a new synonymy was proposed.

First report of Longidorus mindanaoensis Coomans, De Ley, Jimenez and De Ley, 2012 (Nematoda: Longidoridae) From a Mangrove Forest in Vietnam

Longidorus mindanaoensis was recovered from a mangrove forest in Vietnam. The recovered population is in general morphological agreement with the type population, and the characters of pharyngeal bulb, i.e. the same unique pattern of pharyngeal glands nuclei as well as the lip region morphology, amphidial fovea shape and size and position of vulva corroborated its identity. Molecular studies of the recovered population using D2–D3 expansion segments of large subunit ribosomal DNA (LSU rDNA D2–D3) revealed the D2–D3 sequence of recovered population is 99.6% similar to the sequence of the type population. A new morphometric range for body size was recorded for the species based upon present Vietnamese population, and present study emphasized the diversity of Longidorus spp. in Vietnam could be higher than previously assumed.

Genetic diversity, and description of a new dagger nematode, Xiphinema afratakhtehnsis sp. nov., (Dorylaimida: Longidoridae) in natural forests of southeastern Gorgan, northern Iran

The most prevalent dagger nematode recovered from rhizospheric soil samples of forest trees in the Afrātakhteh region of Golestan province (Iran) was Xiphinema afratakhtehnsis sp. nov. and it is described and illustrated with integrative approaches using both morphological and molecular criteria. It belongs to the morphospecies group 6 of the intragenic historical grouping of Xiphinema non-americanum species. The new species is characterized by females with 3.3–4.9 mm sized body, lip region separated from the rest of body by a depression, anteriorly expanded, 16–18 μm wide, vulva located at 47.2–58.5%, odontostyle 155–173 μm and odontophore 89–107 μm long, female genital system composed of two equally developed branches, the tubular part of each having spines, short symmetrically rounded female tail to symmetrically rounded with a small mucro-like projection at the end in a few females, rare males (n = 1 out of 74 females) with 83 μm long dorylaimoid spicules and four juvenile developmental stages. The third-stage juveniles (J3) have a characteristic tail shape (short, symmetrically conical with a club-shaped long mucro) demarcating the species, and being typologically useful for its separation from closely similar species (except X. cohni, with currently no data on its juvenile stages) viz. X. adenohystherum, X. iranicum, X. mazandaranense, X. nuragicum, X. pyrenaicum, X. robbinsi, X. sphaerocephalum and X. zagrosense. Molecular phylogenetic studies using genomic (partial large subunit and internal transcribed spacer 1 ribosomal RNA genes: D2-D3 and ITS1 rDNA) and mitochondrial cytochrome c oxidase subunit I gene (COI mtDNA) revealed the new species forming a unique lineage in all reconstructed trees using Bayesian inference (BI) and maximum likelihood (ML) methods. The sequenced isolates of the new species formed a monophyletic group in the D2-D3 tree. The sequenced isolates of the new species for their COI mtDNA formed four subclades in COI mtDNA phylogeny, and four haplotypes in corresponding analysis.