Can parasitoid strains from different hosts and over four generations modify the chemotactic behavior and parasitism of Aphidius platensis?

Aphidius platensis Brèthes (Hymenoptera: Braconidae) is a parasitoid of cereal aphids. Its foraging, recognition, and host acceptance processes may be related to chemical cues inherited from the host during development. This study aimed to evaluate the influence of the maternal host, that is, Rhopalosiphum padi (L.) (Rp), Schizaphis graminum (Rondani) (Sg) (from the Aphidini tribe), Metopolophium dirhodum Walker (Md), and Sitobion avenae (Fabricius) (Hemiptera: Aphididae) (from the Macrosiphini tribe) (all Hemiptera: Aphididae) on parasitism and chemotactic responses of A. platensis. Parasitism by A. platensis was investigated in non-choice bioassays along four generations, as well as in choice bioassays. Females originating from a S. graminum laboratory colony (SgLab) were reared for four generations on all four aphid species. Chemotaxis experiments were conducted in a four-armed olfactometer with two A. platensis strains: one originated from SgLab and another after three generations on Rp (RpF4), both exposed to the four aphid species simultaneously. The highest SgLab A. platensis parasitism rates, in both choice and non-choice tests, were observed on S. graminum, followed by R. padi and S. avenae. No parasitized hosts were found in M. dirhodum. Furthermore, SgLab A. platensis exhibited a stronger attraction to the odors emitted by S. graminum. However, after the third generation on R. padi (RpF4), A. platensis behavior altered, displaying a preference for R. padi over S. graminum, both in terms of parasitism and chemotactic responses. In conclusion, A. platensis showed a preference for hosts within the Aphidini tribe, indicating innate affinities. Nevertheless, its preference can be modified within this tribe based on the chemical cues inherited from the host during development.