title: Detrimental and neutral effects of a wild grass-fungal endophyte symbiotum on insect preference and performance.
abstract: Seed-borne Epichloë/Neotyphodium Glenn, Bacon, Hanlin (Ascomycota: Hypocreales: Clavicipitaceae) fungal endophytes in temperate grasses can provide protection against insect attack with the degree of host resistance related to the grass-endophyte symbiotum and the insect species involved in an interaction. Few experimental studies with wild grass-endophyte symbiota, compared to endophyte-infected agricultural grasses, have tested for anti-insect benefits, let alone for resistance against more than one insect species. This study quantified the preference and performance of the bird cherry oat-aphid, Rhopalosiphum padi (L.) (Hemiptera: Aphididae) and the cereal leaf beetle, Oulema melanopus (L.) (Coleoptera: Chrysomelidae), two important pests of forage and cereal grasses, on Neotyphodium-infected (E+) and uninfected (E-) plants of the wild grass Alpine timothy, Phleum alpinum L. (Poales: Poaceae). The experiments tested for both constitutive and wound-induced resistance in E+ plants to characterize possible plasticity of defense responses by a wild E+ grass. The aphid, R. padi preferred E- over E+ test plants in choice experiments and E+ undamaged test plants constitutively expressed antibiosis resistance to this aphid by suppressing population growth. Prior damage of E+ test plants did not induce higher levels of resistance to R. padi. By contrast, the beetle, O. melanopus showed no preference for E+ or E- test plants and endophyte infection did not adversely affect the survival and development of larvae. These results extend the phenomenon of variable effects of E+ wild grasses on the preference and performance of phytophagous insects. The wild grass- Neotyphodium symbiotum in this study broadens the number of wild E+ grasses available for expanded explorations into the effects of endophyte metabolites on insect herbivory.
authors.affiliation: USDA, ARS Plant Germplasm Introduction and Testing Research Unit, 59 Johnson Hall, Washington State University, Pullman, WA 99164-6402, USA. stephenclement08@gmail.com
authors.forename: Stephen L
authors.initials: SL
authors.lastname: Clement
authors.forename: Jinguo
authors.initials: J
authors.lastname: Hu
authors.forename: Alan V
authors.initials: AV
authors.lastname: Stewart
authors.forename: Bingrui
authors.initials: B
authors.lastname: Wang
authors.forename: Leslie R
authors.initials: LR
authors.lastname: Elberson
mesh_terms: D000818:Animals; D001042:Aphids / Q000502:physiology*; D001517:Coleoptera / Q000502:physiology*; D055329:Epichloe / Q000502:physiology*; D005260:Female; D006790:Host-Parasite Interactions; D031784:Phleum / Q000382:microbiology* / Q000469:parasitology; D016133:Polymerase Chain Reaction; D013559:Symbiosis