SummaryBasilaphelenchus brevicaudatusn. sp., the third species of this apparently rare genus, is described and illustrated. It was recovered from wood and bark samples from a dead forest tree in the Golestan province of northern Iran. It is typologically characterised by female body length (448 (365-492) μm), three lines in the lateral fields, raised cephalic region having a sclerotised vestibule and cephalic framework, stylet thin with delicate conus and thicker shaft, both parts lacking a visible lumen, and with three elongate, backwardly directed knobs, small, spherical to spade-shaped metacorpus with small, posteriorly located valve (at 72 (58-74)% of metacorpus length), simple vulva without flap at 72.5 (69-78)% of body length, post-vulval uterine sac 32.4 (29.0-37.0) μm long, functional rectum and anus, female tail conical, short (c′ = 2.6 (1.9-3.3) in female, and 2.5 (2.3-2.8) in male), dorsally convex and ventrally concave with blunt end or having a small mucron, both forms with a hyaline-like tip. Males common, with well-curved 9.2 (9.0-10.5) μm long spicules measured along the mid-line, three pairs of small caudal papillae (lacking the single P1 ventral papilla) and no bursa at tail tip, but with hyaline region, similar to females.Basilaphelenchus brevicaudatusn. sp. is compared with the two currently known species of the genus, the type species,B. persicus, andB. grosmannae. Molecular phylogenetic inferences using partial sequences of small and large subunit ribosomal RNA genes (SSU and LSU) from different isolates of the new species revealed that it belongs to the Tylaphelenchinae clade.

Summary Two populations of an aphelenchoidid nematode were recovered from natural forests in Golestan province, Iran. Both populations resembled each other morphologically. The females of the first population, from rotten wood of Fagus orientalis in Golestan National Park, measured 294-338 μm long, and females of the second population, from forests of Ramian county, measured 365-464 μm long. A reverse taxonomic approach, based upon SSU and LSU phylogenies using a maximal number of Aphelenchoididae genera, revealed the two isolates to be conspecific and representatives of a new species of Basilaphelenchus. Basilaphelenchus magnabulbus n. sp. is described and illustrated herein and is mainly characterised by the unique form of the metacorpus, this being elongate and filling the corresponding body region similar to the common form in other aphelenchoidids (vs smaller with well posteriorly located small valve in previously described species of the genus). The new species has an elevated lip region, fine stylet with three elongate posteriorly directed knobs, female tail elongate conoid and ventrally bent, and male tail short conical with three pairs of caudal papillae. It was morphologically compared with four previously known species of the genus, viz., B. persicus, B. brevicaudatus, B. gorganensis and B. grosmannae, and three species of Aphelenchoides having a broadly similar morphology.

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.

Basilaphelenchus gorganensis n. sp. is described and illustrated from wood and bark of a dead tree from northern Iran. The new species is characterized by female body length (415–559 µm), three‐lined lateral fields, a sclerotized cephalic vestibule and cephalic framework, thin stylet with three elongate backwardly directed knobs, small spherical to oval metacorpus, with small and posteriorly located valve, simple vulva without any flap apparatus, 59‐ to 79‐µm‐long post‐vulval uterine sac, functional rectum and anus and dorsally convex, ventrally concave, usually ventrally bent conical female tail with a sharp tip. Males are common, apparently functional and characterized by well‐curved spicules, three pairs of small caudal papillae and no bursa at tail tip. Molecular phylogenetic inferences using partial sequences of small and large subunit ribosomal RNA genes (SSU and LSU rDNA) from different isolates of the new species revealed it differs from currently sequenced species and belongs to the Tylaphelenchinae clade.

A population of Xiphinema americanum-group was recovered in association with stone fruit trees in Isfahan province, center of Iran. A reverse taxonomic approach based upon the large subunit ribosomal DNA (LSU rDNA D2-D3) and the mitochondrial cytochrome c oxidase subunit I (COI mtDNA) gene sequences in integration with morphological studies, revealed that the recovered population belongs to Xiphinema santos. The Iranian population was mainly characterized by 1240-1868 µm long females with 60-84 µm long odontostyle, a= 37.2-51.9 and c=42.8-54.6. It is further characterized by a lip region having a shallow depression in junction with the body, presence of visible endosymbiont bacteria in ovaries under light microscope (LM), dorsally convex and ventrally slightly concave conical tail with blunt tip and three juvenile developmental stages.This population was identical with the type population in its morphology; however overlapped and extended morphometric data ranges as well as differences in some indexes were observed. Compared to a Spanish population of this species, the Iranian population had an identical morphology, similar morphometric data ranges and identical LSU and COI sequences. In LSU phylogeny, the relationship between the present and some previously sequenced isolates of the species and some isolates of three species X. georgianum, X. laevistriatum and X. citricolum was not resolved. In COI phylogeny, the clade of the Iranian and Spanish populations appeared as an independent lineage inside a major clade including several species. The comparison with other populations of the species was reported and discussed. A second species, X. primum, that is native to Iran was recovered from a new locality and characterized molecularly.