Incidence of Oscheius onirici (Nematoda: Rhabditidae), a potentially entomopathogenic nematode from the marshlands of Wisconsin, USA.

Weimin Ye,Shane Foye,Ann E Macguidwin,Shawn Steffan

doi:10.21307/jofnem-2018-004

Abstract

In a search for an entomopathogenic nematode to control cranberry insect pests, three Oscheius populations (Rhabditidae) were recovered through the Galleria-bait method from one sample taken in a wild cranberry marsh in Jackson County, Wisconsin, USA. Morphological studies with light microscopy and scanning electron microscopy, as well as molecular analyses of the near-full-length small subunit rDNA gene, D2/D3 expansion segments of the large subunit rDNA gene, internal transcribed spacer, and mitochondrial cytochrome oxidase subunit 1 (CoxI) genes revealed this as Oscheius onirici, a species recently described from a karst cave soil of central Italy. The species belongs to the dolichura-group and is characterized by its DNA sequences; hermaphroditic reproduction; and males not found. A Bacillus-like bacterium appears to be associated with this nematode based on our microscopic and SEM observations; however its identity and persistent association with the nematode has not been confirmed. Nonetheless, this nematode is capable of infecting and killing the sparganothis fruitworm Sparganothis sulfureana Clemens (Lepidoptera: Tortricidae), the brown-banded cockroach Supella longipalpa Fabricius (Blattodea: Ectobiidae), and the cranberry fruitworm Acrobasis vaccinii Riley (Lepidoptera: Pyralidae), under laboratory conditions, and each in less than 72 hr. The mealworm Tenebrio molitor Linnaeus (Coleoptera: Tenebrionidae) and the greater wax moth Galleria mellonella Linnaeus (Lepidoptera: Pyralidae), are also susceptible, but take 3.5 and 5.2 days to die, respectively. This species is a new potential bio-control agent on insects.

Highlights

Nematodes can be considered as entomopathogenic if they fulfill the following criteria for entomopathogenicity: bearing a pathogenic bacterium within a dauer juvenile nematode, releasing the bacterium within the host, active host-seeking and -penetration by dauer juveniles, rapid insect death, nematode and bacterial reproduction, reassociation of the pathogenic bacteria with new generations of dauer juveniles; and emergence of IJs from the cadaver so that the cycle can be repeated (Dillman et al, 2012)
Heterorhabditidoides was proposed as a new genus (Zhang et al, 2008), but it was considered as a junior syno nym of Oscheius (Ye et al, 2010) and it is in general not accepted as a valid genus (Liu et al, 2012; Campos-Herrera et al, 2015; Torrini et al, 2015; Tabassum et al, 2016; Valizadeh et al, 2017)
Nematodes of the genera Steinernema and Heterorhabditis, are often entomopathogenic, and as such, they have been used as bio-control agents to suppress pest populations (Kaya and Gaugler, 1993)

Summary

Introduction

Nematodes can be considered as entomopathogenic if they fulfill the following criteria for entomopathogenicity: bearing a pathogenic bacterium within a dauer ( known as infective) juvenile nematode, releasing the bacterium within the host, active host-seeking and -penetration by dauer juveniles, rapid insect death, nematode and bacterial reproduction, reassociation of the pathogenic bacteria with new generations of dauer juveniles; and emergence of IJs from the cadaver so that the cycle can be repeated (Dillman et al, 2012). Heterorhabditidoides was proposed as a new genus (Zhang et al, 2008), but it was considered as a junior syno nym of Oscheius (Ye et al, 2010) and it is in general not accepted as a valid genus (Liu et al, 2012; Campos-Herrera et al, 2015; Torrini et al, 2015; Tabassum et al, 2016; Valizadeh et al, 2017) Another species, Heterorhabditidoides rugaoensis, was transferred to Oscheius (Darsouei et al, 2014; Tabassum et al, 2016). Nematodes of the genera Steinernema and Heterorhabditis, are often entomopathogenic, and as such, they have been used as bio-control agents to suppress pest populations (Kaya and Gaugler, 1993). This paper presented the characterization of this nematode through combined approaches by morphological and molecular analysis to determine its identity and tested its entomopathogenicity

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