Morphological and molecular characterization of Hoplolaimus pararobustus (Schuurmans Stekhoven and Teunissen, 1938) Sher 1963 with its first report on Zea mays roots in Namibia

Abstract

In the summer of 2018, specimens of a Hoplolaimus population were extracted from a maize root sample collected near Stampriet, Namibia. This population was identified as Hoplolaimus pararobustus and is described and illustrated based on its morphological, morphometric, and molecular characteristics. To our knowledge, this is the first report H. pararobustus from maize roots. Females of the population had a mean body and stylet length of 1,100µm and 36µm, respectively. Esophagus with three nuclei in three pharyngeal glands. Lateral field reduced, ranging from a very faint line to just breaks in striae. The males were shorter than the females with a mean body length of 925µm and the stylet slightly shorter, with a mean length of 34µm. Phylogenetic analyses using partial sequences of 18S and the expansion fragment D2-D3 of 28S rDNA genes showed the close relation of this species and H. columbus. This Namibian population of H. pararobustus is the first Hoplolaimus species from Africa to be molecularly characterized.