Systematic position of the genus Atetylenchus Khan, 1973 (Nematoda: Tylenchidae) with description of two new species.

Summary: Two new and one known species of Atetylenchus recovered from Dezful, Khuzestan Province, south-western Iran, are illustrated and described using morphological, morphometric and molecular data. Atetylenchus dezfuliensis n. sp. is characterised by medium-sized body 700-998 μ m long, stylet 10.0-11.5 μ m long, characteristic tail shape, first tapering regularly but then cylindrical to slightly clavate and 90-136 μ m long, phasmids located at one-third anterior part of tail and short spicules 18.7 μ m long. Atetylenchus longilabiatus n. sp. is characterised by small-sized body 593-720 μ m long, prominent lip region, stylet 9.5-12.5 μ m long, conical tail with hook-shaped terminus and 42-63 μ m long, phasmids located near mid-tail and short spicules 17.5 μ m long. Atetylenchus cf. graminus is characterised by small-sized body 643-787 μ m long, stylet 10.7-11.7 μ m long, vulva located at 51.7-55.1% of the body length, and conical tail with finely rounded end and 63-69 μ m long. Molecular data are provided for the characterisation of this genus from these two new and one known species using ribosomal genes (18S and 28S rRNA). This genus is molecularly separated from Psilenchus , but closely related in both genes. These molecular markers showed different phylogenies for both genera; partial 18S showed their relationship with Tylenchidae, while 28S rRNA showed their relationship with Merliniidae. A key to the genus is provided for species identification. [ABSTRACT FROM AUTHOR]