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

Mariette Marais,Hendrika Fourie,Milad Rashidifard,Esther van den Berg

doi:10.21307/jofnem-2020-124

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 1,100 µm and 36 µm, 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 925 µm and the stylet slightly shorter, with a mean length of 34 µm. Phylogenetic analyses using partial sequences of 18 S and the expansion fragment D2–D3 of 28 S 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.

Highlights

The constructed Bayesian tree using 18 S data set showed that H. pararobustus is in a well-supported clade with two populations of H. galeatus and one population of H. columbus with H. columbus being the closest to the Namibian population of H. pararobustus (Figure 2)
A population of H. pararobustus was recovered from maize roots in Namibia
Hoplolaimus pararobustus is commonly found in Namibia, reported from both cultivated and noncultivated areas, but this is according to our knowledge the first report from maize roots

Summary

Introduction

Hoplolaimus spp., are robust nematodes with a very distinct lip region and welldeveloped stylet with distinctly shaped stylet knobs (Fortuner, 1991) that feed on a wide range of plants and have a global distribution. Bae et al (2009) reported that Handoo and Golden (1992) recognized 29 species in the genus Hoplolaimus Von Daday, 1905. Siddiqi (2000) listed 32 species in three subgenera with two species Hoplolaimus johani Tiwari, Mishra and Malhotra, 2001 and Hoplolaimus caudifurcatus Tiwari, Mishra and Malhotra, 2001, described in 2001 (Tiwari et al, 2001). Hoplolaimus pararobustus has been reported from inside roots of banana (Whitehead, 1959) giving rise to dark-brown pustules that eventually result in necrotic cortical tissue situated around the heads of the feeding sites of the nematodes and eventually elongated ulcerated lesions on the roots (Siddiqi, 1974). It has been reported, at a population density of 200 individuals per gram of tissue, in corms and roots of banana where they were likely to cause damage to the crop (Sikora et al, 2018). This is the first report of H. pararobustus from maize (Z. mays) roots

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