title: Development and population dynamics of Steinernema yirgalemense (Rhabditida: Steinernematidae) and growth characteristics of its associated Xenorhabdus indica symbiont in liquid culture.
abstract: Entomopathogenic nematodes have become a valuable addition to the range of biological control agents available for insect control. An endemic nematode, Steinernema yirgalemense, has been found to be effective against a wide range of key insect pests. The next step would be the mass production this nematode for commercial application. This requires the establishment of monoxenic cultures of both the nematode and the symbiotic bacterium Xenorhabdus indica. First-stage juveniles of S. yirgalemense were obtained from eggs, while X. indica was isolated from nematode-infected wax moth larvae. The population density of the various life stages of S. yirgalemense during the developmental phase in liquid culture was determined. The recovery of infective juveniles (IJs) to the third-stage feeding juveniles, was 67 ± 10%, reaching a maximum population density of 75,000 IJs ml- 1 on day 13 after inoculation. Adult density increased after 8 days, with the maximum female density being 4600 ml- 1 on day 15, whereas the maximum male density was 4300 ml- 1 on day 12. Growth curves for X. indica showed that the exponential phase was reached 15 h after inoculation to the liquid medium. The stationary phase was reached after 42 h, with an average of 51 × 107 colony-forming units ml- 1. Virulence tests showed a significant difference in insect mortality between in vitro- and in vivo-produced nematodes. The success obtained with the production of S. yirgalemense in liquid culture can serve as the first step in the optimizing and upscaling of the commercial production of nematodes in fermenters.
authors.affiliation: Department of Conservation Ecology and Entomology,Faculty of AgriSciences,Private Bag X1, Matieland7602,Stellenbosch,South Africa.
authors.forename: T
authors.initials: T
authors.lastname: Ferreira
authors.affiliation: Department of Conservation Ecology and Entomology,Faculty of AgriSciences,Private Bag X1, Matieland7602,Stellenbosch,South Africa.
authors.forename: M F
authors.initials: MF
authors.lastname: Addison
authors.affiliation: Department of Conservation Ecology and Entomology,Faculty of AgriSciences,Private Bag X1, Matieland7602,Stellenbosch,South Africa.
authors.forename: A P
authors.initials: AP
authors.lastname: Malan
mesh_terms: D000818:Animals; D005260:Female; D008297:Male; D009036:Moths / Q000469:parasitology; D011157:Population Dynamics; D017168:Rhabditida / Q000254:growth & development* / Q000382:microbiology* / Q000472:pathogenicity; D016019:Survival Analysis; D014774:Virulence; D020593:Xenorhabdus / Q000254:growth & development*