title: Multifaceted effects of host plants on entomopathogenic nematodes.
abstract: The success of parasites can be impacted by multi-trophic interactions. Tritrophic interactions have been observed in parasite-herbivore-host plant systems. Here we investigate aspects of multi-trophic interactions in a system involving an entomopathogenic nematode (EPN), its insect host, and host plant. Novel issues investigated include the impact of tritrophic interactions on nematode foraging behavior, the ability of EPNs to overcome negative tritrophic effects through genetic selection, and interactions with a fourth trophic level (nematode predators). We tested infectivity of the nematode, Steinernema riobrave, to corn earworm larvae (Helicoverpa zea) in three host plants, tobacco, eggplant and tomato. Tobacco reduced nematode virulence and reproduction relative to tomato and eggplant. However, successive selection (5 passages) overcame the deficiency; selected nematodes no longer exhibited reductions in phenotypic traits. Despite the loss in virulence and reproduction nematodes, first passage S. riobrave was more attracted to frass from insects fed tobacco than insects fed on other host plants. Therefore, we hypothesized the reduced virulence and reproduction in S. riobrave infecting tobacco fed insects would be based on a self-medicating tradeoff, such as deterring predation. We tested this hypothesis by assessing predatory success of the mite Sancassania polyphyllae and the springtail Sinella curviseta on nematodes reared on tobacco-fed larvae versus those fed on greater wax moth, Galleria mellonella, tomato fed larvae, or eggplant fed larvae. No advantage was observed in nematodes derived from tobacco fed larvae. In conclusion, our results indicated that insect-host plant diet has an important effect on nematode foraging, infectivity and reproduction. However, negative host plant effects, might be overcome through directed selection. We propose that host plant species should be considered when designing biocontrol programs using EPNs.
authors.affiliation: Adnan Menderes University, Faculty of Arts and Sciences, Department of Biology, 09100 Aydin, Turkey; Southeastern Fruit and Tree Nut Research Laboratory, USDA-ARS, Byron, GA 31008, USA. Electronic address: Selcuk.Hazir@gmail.com.
authors.forename: Selcuk
authors.initials: S
authors.lastname: Hazir
authors.affiliation: Southeastern Fruit and Tree Nut Research Laboratory, USDA-ARS, Byron, GA 31008, USA. Electronic address: David.Shapiro@ars.usda.gov.
authors.forename: David I
authors.initials: DI
authors.lastname: Shapiro-Ilan
authors.affiliation: Adnan Menderes University, Aydin Health Services Vocational School, 09100 Aydin, Turkey; Southeastern Fruit and Tree Nut Research Laboratory, USDA-ARS, Byron, GA 31008, USA.
authors.forename: Canan
authors.initials: C
authors.lastname: Hazir
authors.affiliation: Instituto Biologico, APTA, CP 70, Campinas, SP 13001-970, Brazil; Southeastern Fruit and Tree Nut Research Laboratory, USDA-ARS, Byron, GA 31008, USA.
authors.forename: Luis G
authors.initials: LG
authors.lastname: Leite
authors.affiliation: Adnan Menderes University, Faculty of Agriculture, Department of Plant Protection, 09100 Aydin, Turkey.
authors.forename: Ibrahim
authors.initials: I
authors.lastname: Cakmak
authors.affiliation: USDA-ARS, CPRMU, Tifton, GA, USA.
authors.forename: Dawn
authors.initials: D
authors.lastname: Olson
mesh_terms: D000222:Adaptation, Physiological; D000704:Analysis of Variance; D000818:Animals; D006790:Host-Parasite Interactions / Q000502:physiology*; D018551:Solanum lycopersicum / Q000469:parasitology* / Q000502:physiology; D009036:Moths / Q000469:parasitology* / Q000502:physiology; D012098:Reproduction; D017168:Rhabditida / Q000472:pathogenicity / Q000502:physiology*; D012692:Serial Passage; D032323:Solanum melongena / Q000469:parasitology* / Q000502:physiology; D014026:Nicotiana / Q000469:parasitology* / Q000502:physiology; D014774:Virulence
keywords: Biological control; Eggplant; Entomopathogenic nematodes; Helicoverpa zea; Host diet; Steinernema riobrave; Tobacco; Tomato; Trophic relationships