Detrimental and neutral effects of a wild grass-fungal endophyte symbiotum on insect preference and performance
1USDA, ARS Plant Germplasm Introduction and Testing Research Unit, 59 Johnson Hall, Washington State University, Pullman, WA 99164-6402, USA
2PGG Wrightson Seeds, PO Box 175, Lincoln, New Zealand
3Huazhong Agricultural University, Wuhan, China
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.
Keywords: Aphididae, Chrysomelidae, grass endophyte, insect herbivory, host-plant resistance, Oulema melanopus, Rhopalosiphum padi, wild grass Phleum alpinum
Abbreviations: BYDV, barley yellow dwarf virus; E+, endophyte infected; E-, endophyte uninfected
Correspondence:
a* stephenclement08@gmail.com,
b jinguo.hu@ars.usda.gov,
c astewart@pggwrightsonseeds.co.nz,
d brwang@mail.hzau.edu.cn,
e elberson@wsu.edu, *Corresponding author
Received: 10 May 2010 | Accepted: 20 October 2010 | Published: 29 June 2011
Copyright: This is an open access paper. We use the Creative Commons Attribution 3.0 license that permits unrestricted use, provided that the paper is properly attributed.
ISSN: 1536-2442 | Volume 11, Number 77
Clement SL, Hu J, Steward AV, Wang B, Elberson LR. 2011. Detrimental and neutral effects of a wild grass-fungal endophyte symbiotum on insect preference and performance. Journal of Insect Science 11:77 available online: insectscience.org/11.77
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