Morphological and molecular characterisation of one new and two known predominant telotylenchid species (Rhabditida: Telotylenchinae) associated with vegetable crops in Bushehr province, southern Iran

Summary Stunt nematodes of the subfamily Telotylenchinae (Nematoda: Tylenchoidea) are ectoparasitic nematodes commonly found in the rhizosphere of diverse agricultural crops. In this study, we used morphological and molecular approaches to characterise a new species, Tylenchorhynchus bushehrensis n. sp., along with two known species, T. brassicae and Bitylenchus ventrosignatus , which are predominant in vegetable production ecosystems of Bushehr province, southern Iran. The new species is characterised by a medium body size (527-751 μ m), a semi-rounded lip region with 3-5 transverse annuli slightly offset from the body contour, a short stylet (13-15 μ m) with rounded knobs directed laterally or posteriorly, an intestine that does not end in a post-rectal sac, a conoid tail with 12-20 annuli ending in a finely rounded terminus, and short spicules (<20 μ m). Morphologically, it closely resembles T. brassicae , but a shorter stylet (13-15 μ m vs 15-19 μ m) and the absence of intestinal fasciculi distinguish it from T. brassicae . An independent approach was used to verify the validity of the new species and to check its relatedness to T. brassicae . Phylogenetic analyses were conducted using molecular data from the D2-D3 expansion segments of the large ribosomal subunit (28S rDNA), the partial small ribosomal subunit (18S rDNA) and the partial sequence of the internal transcribed spacer 1 (ITS1). The results revealed a close phylogenetic relationship between T. bushehrensis n. sp. and T. brassicae in reconstructed trees. However, the 28S rDNA and ITS trees provided sufficient resolution to support their distinction as separate species. Data of the Bushehr populations of the two species T. brassicae and Bitylenchus ventrosignatus were also provided.