Development and population dynamics of Steinernema yirgalemense (Rhabditida: Steinernematidae) and growth characteristics of its associated Xenorhabdusindica 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.

Potential of Local Entomopathogenic Nematodes for Control of the Vine Mealybug, Planococcus ficus

“…Van Niekerk and Malan (2012) also screened six indigenous EPN species for pathogenicity to P. citri, finding H. zealandica and S. yirgalemense to be the most effective. In this study, S. yirgalemense was selected for further testing, as other studies have also proven this species to be the most effective against codling (De Waal et al 2011;Odendaal et al 2016) and false codling moth (Malan & Moore, 2016), with the potential to be mass cultured (Ferreira et al, 2016). However, should the mass-culture methods for heterorhabditid species being developed in South Africa succeed, H. noenieputensis would be an excellent candidate for the control of P. ficus.…”

Production of entomopathogenic nematodes in submerged monoxenic culture: A review

“…At the beginning of its development, a lag phase of 0–15 hr occurs. The exponential phase begins after 15 hr, followed by the stationary phase after 42 hr (Ferreira et al, 2016; Yoo et al, 2001). However, this growth timing is not a general rule.…”

“…The biotechnological challenge to improve the performance of the culture process makes it necessary the control of physiology of symbiotic bacteria, formulation of culture medium (Chavarría‐Hernández, Espino‐García, Sanjuan‐Galindo, & Rodríguez‐Hernández, 2006; Islas‐López, Sanjuan‐Galindo, Rodríguez‐Hernández, & Chavarría‐Hernández, 2005; Leite, Shapiro‐Ilan, Hazir, & Jackson, 2016a; Masurekar, 2008; Yoo, Brown, Cohen, & Gaugler, 2001), and process parameters, such as oxygen transfer rate, temperature, pH (Ferreira, Addison, & Malan, 2016), inoculum size and timing of inoculation (Johnigk, Ecke, Poehling, & Ehlers, 2004), EPN sensitivity to shear and normal stresses, IJ recovery, geometry, and configuration of the bioreactor (Chavarría‐Hernández, Sanjuan‐Galindo, Rodríguez‐Pastrana, Medina‐Torres, & Rodríguez‐Hernández, 2007; Neves, Simões, & Mota, 2001) among others.…”

Entomopathogenic nematodes, potential industrial pest control agents: A South African perspective

“…Only flask-cultures of H. zealandica (Ferreira et al, 2014), S. innovationi (Ramakuwela et al, 2016) and S. yirgalemense (Ferreira et al, 2015) have been obtained despite several attempts for in vitro mass culturing (Hatting et al, 2018). Currently, only an imported formulation based on H. bacteriophora is produced and commercialized under the name Cryptonem® (Hatting et al, 2018).…”