First morphological and molecular characterization of Psilenchus hilarulus de Man, 1921 (Nematoda: Psilenchidae) from Iraq

During a survey on the biodiversity of plant-parasitic nematodes in the Misan province, southeast Iraq, a population of Psilenchus hilarulus was discovered around the rhizosphere of okra. The study included the analysis of the morphological and morphometric characteristics of the species that were recovered. These characteristics were then compared to those of other populations that have been reported from other locations. The phylogenetic relationships of the Iraqi population of P. hilarulus with representatives of tylenchid taxa were reconstructed using the partial sequences of the small subunit (SSU), D2-D3 expansion segments of large subunit (LSU), and internal transcribed spacer (ITS) regions of ribosomal DNA, based on Bayesian inference. In the phylogenetic trees inferred from SSU and LSU sequences, the sequences of genus Psilenchus formed a clade separate from the representatives of Tylenchidae and Merliniidae. In the SSU tree, the Iraqi population occupied a placement inside a major clade that includes the sequences assigned to P. hilarulus, P. cucrumerus and Psilenchus sp. In LSU tree, new LSU sequences formed a clade with a major clade that includes sequences assigned to P. hilarulus, P. cucrumerus and P. vinciguerrae. The first ITS sequence of the genus, the ITS rDNA of the Iraqi population of P. hilarulus, was utilized to reconstruct and analyze the corresponding phylogenetic tree. This appears to be the initial documentation of P. hilarulus emerging from Iraq.