Taxonomical considerations and molecular phylogeny of the closely related generaBitylenchus,SauertylenchusandTylenchorhynchus(Nematoda: Telotylenchinae), with one new and four known species from Iran

Abstract

During several nematological surveys in cultivated and natural habitats in Khuzestan and Zanjan provinces of Iran, a new species, Bitylenchus parvulus n. sp., two new records for Iran – namely, Tylenchorhynchus agri and Tylenchorhynchus graciliformis – and a population of Bitylenchus parvus and one of Sauertylenchus maximus were recovered and characterized based upon morphological and molecular approaches. The new species is characterized by lip region with five to seven annuli, stylet 17.7 (17.0–18.5) μm long, sub-cylindrical tail narrowing abruptly near terminus giving a bluntly digitate shape to the tail tip, cuticle near anterior part of vulva wrinkled and post-rectal sac occupies whole of tail cavity. The phylogenetic analyses were carried out using molecular data from D2–D3 expansion segments of large ribosomal subunit (28S rRNA) for all studied species and the partial small ribosomal subunit (18S rRNA) for the new species. The representatives of Bitylenchus and Sauertylenchus formed distinct clades from Tylenchorhynchus members, supporting the hypothesis in which Bitylenchus and Sauertylenchus could be considered as valid genera, but rejecting the ‘large-genus’ concept for Tylenchorhynchus. Also, Sauertylenchus ibericus was proposed as a junior synonym of S. maximus based on the results from morphological and phylogenetic analysis. Furthermore, an identification key for all known species included in the three genera Bitylenchus, Tylenchorhynchus and Sauertylenchus is presented herein. The number of transverse annuli on the lip region and presence/absence of post-rectal sac were considered as the main diagnostic characters for classifying the species into seven groups, and other morphological and morphometric characters were subsequently used for distinguishing species in each group.

First report of Bitylenchus ventrosignatus (Tobar Jiménez, 1969) Siddiqi, 1986 associated with wild grass in Botswana

“…Furthermore, the SEM study and mtDNA (e.g., COI) may reveal the species’ real position belongs to Bitylenchus . Overall, the current study’s findings were in agreement with other Bitylenchus 18 S and 28 S rDNA phylogenies ( Handoo et al, 2014 ; Hosseinvand et al, 2020 ). Two permanent microscope slides containing the five females and five males were deposited in the Nematology collection of the University of Limpopo, South Africa.…”

“…This character has been described in the original description for B. ventrosignatus (Geraert et al, 1975;Geraert, 2011;Tobar Jiménez, 1969). Irregular line undulation has been described for B. parvulus Hosseinvand et al, 2020; however, they differ with the tested species in body length (496-583 vs 542-834 µm), stylet length (13-14 vs 17-18.5 µm), and tail length (35-44 vs 42-59 µm).…”

“…This is in agreement with Handoo et al (2014) . Besides, the results obtained by Hosseinvand et al (2020) indicated that Bitylenchus species divide into two groups. However, more sequences should be included aiming for the phylogenetic study, albeit the species identification of the genus Bitylenchus is problematic.…”

“…However, compared with T. fatimae JOURNAL OF NEMATOLOGY Figure 4: The Bayesian tree inferred from known and newly sequenced Bitylenchus ventrosignatus from Botswana based on the 28 S rDNA region. Khan et al, 2004, they differ in the basal bulb (pyriform vs cylindrical), gubernaculum length (8-9 vs 11.5-12 µm), and irregular undulation at the posterior part of the vulva (present vs absent) (see Geraert, 2011). Morphometrical differences of the Botswanan population compared with the other populations of the same species are considered a geographical distribution, and therefore, the present species identified as B. ventrosignatus.…”

“…The genus Bitylenchus belongs to the family Dolichodoridae Chitwood in Chitwood, 1950. This genus has been synonymized with Tylen chorhynchus (Geraert, 2011). However, Handoo et al (2014) and Hosseinvand et al (2020) considered it as a valid taxon using molecular analysis. Siddiqi (2000) considered 29 valid species under the genus Bitylenchus.…”