On the synonymy of Trophotylenchulus asoensis and T. okamotoi with T. arenarius, and intra-generic structure of Paratylenchus (Nematoda: Tylenchulidae)

Abstract

Two populations of the genus Trophotylenchulus and 10 species of the genus Paratylenchus from Iran were characterized based on morphometric, morphological and molecular characters. Our observations on the two populations of Trophotylenchulus from Iran revealed that T. asoensis and T. okamotoi have been distinguished from T. arenarius, on the basis of the features which cannot be longer considered as stable diagnostic characters. One of the populations shows a mixed combination of the characters of T. arenarius and T. asoensis; it has morphometrics more similar to T. arenarius but shows affinities with T. asoensis in the tail terminus shape of females and second-stage juveniles (J2) and in having a reduced stylet in males. The other population fit well with T. okamotoi; it has females with generally bluntly rounded tails typical for T. okamotoi, but sometimes with finely rounded tail termini, like those of T. arenarius or T. asoensis. The sequences of D2-D3 expansion segments of 28 S rRNA gene for the two populations are identical with each other, but only 4 bp (0.67%) difference with T. arenarius sequence deposited in the GenBank. Considering no stable difference allow separating species, synonymy of T. asoensis and T. okamotoi with T. arenarius, which has already been proposed, is supported and confirmed here. All studied Paratylenchus species with stylets longer than 40 µm, except P. straeleni, formed a basal cluster to Cacopaurus pestis and species of Paratylenchus bearing stylets shorter than 40 µm; thus, validity of Gracilacus cannot be rejected using our data sets. However, the synonymy of Paratylenchoides was supported by the positioning of P. sheri within representatives of Paratylenchus in the inferred phylogenetic tree.

Species Diversity of Pin Nematodes (Paratylenchus spp.) from Potato Growing Regions of Southern Alberta, Canada

“…The possible presence of species complexes in pin nematodes was highlighted by Van den Berg et al [28] and Mirbabaei et al [40]. We are in agreement with the authors that similar appearances and overlapping morphometrical characters may present difficulties in ascertaining species status.…”

“…Ghaderi et al [25] accepted the synonymization of P. similis and P. tateae; however, with the availability of molecular data, the same authors [23] rejected the change and referred to both species as valid taxa, and also commented that several populations of P. similis may indeed be P. tateae. Bahmani et al [44] also presented a detailed argument on the validity of P. labiosus, which was supported by molecular data in Mirbabaei et al [40].…”

“…Our phylogenetic analysis of D2-D3 expansion domains of the 28S rRNA also indicates that the status of P. nanus type B [28] and P. sheri [40] need detailed revision. By comparing all the available molecular and morphometric data from both species, it is evident that P. nanus type B is a population of P. neoprojectus and P. sheri is a population of P. tateae.…”

“…nanus type B) and P. coronatus (MK506808). It is also noted that the sequence of P. sheri (MN088374) provided by Mirbabaei et al [40] grouped with the Canadian and Spanish populations of P. tateae. The molecular identities suggest that this sequence belongs to P. tateae instead of P. sheri.…”

Integrative Taxonomy and Molecular Phylogeny of the Plant-Parasitic Nematode Genus Paratylenchus (Nematoda: Paratylenchinae): Linking Species with Molecular Barcodes

“…by using 58 28S rRNA and 40 ITS rRNA gene sequences. Several other studies provided additional molecular characterisations, phylogenetic analyses and descriptions of new Paratylenchus species [ 14 , 25 , 32 , 33 , 34 , 35 , 36 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 ]. In a study by Hesar et al [ 24 ], 28S rRNA and ITS rRNA gene sequences of several Paratylenchus spp.…”