Steinernema populi n. sp. (Panagrolaimomorpha, Steinernematidae), a new entomopathogenic nematode species from China.

Steinernema populi n. sp. was recovered by baiting from beneath poplar trees in China. Morphological and molecular features provided evidence for placing the new species into the Kushidai clade. The new species is characterized by the following morphological features: third-stage infective juveniles (IJ) with a body length of 1095 (973-1172) µm, a distance from the anterior end to excretory pore of 77 (70-86) µm and a tail length of 64 (55-72) µm. The Body length/Tail length (c) ratio and Anterior end to Excretory pore/ Tail length × 100 (E%) of S. populi n. sp. are substantially greater than those of all other 'Feltiae-Kushidai-Monticolum' group members. The first-generation males can be recognized by a spicule length of 66 (57-77) µm and a gubernaculum length of 46 (38-60) µm. The new species is further characterized by sequences of the internal transcribed spacer and partial 28S regions of the ribosomal DNA. Phylogenetic analyses show that Steinernema akhursti and Steinernema kushidai are the closest relatives to S. populi n. sp.