Filenchus spirocaudatus sp. n. (Tylenchomorpha: Tylenchidae) from the rhizosphere of wheat in Isfahan province, Iran: morphological and molecular characterisation

Summary

A new species of the genus Filenchus, F. spirocaudatus sp. n., recovered from a wheat (Triticum aestivum) field in Isfahan province, Iran, is described and illustrated based on light microphotographs and scanning electron microscopy, as well as molecular data (partial small subunit ribosomal DNA, SSU rDNA). The new species is mainly characterised by its terminal tail annulus, which is irregularly twisted in all examined specimens and appears star-like under light microscopy. Females (387-453 μm long) possess an annulated lip region, amphidial openings short longitudinal lateral slits, small lateral vulval flaps, and an elongate-conoid tail. Morphological and morphometric differences from three closely similar species, viz. F. australis, F. microdorus and F. misellus, are discussed. Filenchus misellus is considered a cryptic form relative to the new species, but F. spirocaudatus sp. n. is distinguished from it and the other congeners primarily by tail tip morphology and molecular evidence. Phylogenetic relationships with other relevant genera and species were inferred from a partial SSU rDNA sequence. In the resulting tree, the SSU sequence of F. spirocaudatus sp. n. formed a clade with three sequences assigned to F. misellus.