Stabilization of beneficial traits in Heterorhabditis bacteriophora through creation of inbred lines

Serial culturing of organisms used for biological pest suppression often leads to detrimental genetic changes and loss of utility. We established that genetically homozygous inbred lines can deter beneficial trait decline in the entomopathogenic nematode, Heterorhabditis bacteriophora. Three inbred lines and the foundation population were serially cultured in the insect host, Galleria mellonella. Trait stability was evaluated by comparing serially cultured with non-cultured populations. Laboratory data indicated that serial culture of the foundation population (16 passages) resulted in more than a 30% loss in traits deemed beneficial for biological pest suppression i.e., virulence to an insect host (Diaprepes abbreviatus), reproductive capacity, heat tolerance (at 38 °C), and hostseeking ability. In contrast, the three inbred lines were impervious to decline in all beneficial traits. A greenhouse test targeting D. abbreviatus provided additional evidence that the biocontrol efficacy of the inbred lines remained stable during serial culture. Our results indicate that genetic factors played an important role in trait change, and creation of inbred lines may be a useful technique for maintaining beneficial traits.