Submitted to: Redia Journal of Zoology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/20/2009
Publication Date: 12/22/2009
Citation: Clement, S.L. 2009. Variable effects of fungal endophyte-infected grasses on the performance of pestiferous aphids. Redia Journal of Zoology. 92:205-209. Interpretive Summary: The USDA, ARS seed bank at Pullman, Washington stores and maintains approximately 80,000 plant accessions of major agricultural crops. Among this material are approximately 20,500 accessions of forage and turf grass accessions, many of which are infected with microbes in the form of Neotyphodium fungal endophytes. Because some of these fungi in grass accessions have anti-insect properties, U.S. and foreign scientists and commerical grass breeders acquire endophyte-infected accessions from the Pullman seed bank for basic research and commercial development of new grass cultivars. Continued development of new cultivars with insect resistance traits linked to Neotyphodium infection is contingent upon more information on the effect of different endophyte-infected accessions on the survival of important grass pests. The research summarized in this paper is important because it shows that infected fescue accessions from the Mediterranean Basin and other Palearctic regions have strong anti-insect properties, therefore providing additional evidence of the existence of diverse grass-endophyte associations in the Pullman seed bank. This research will also highlight the importance of the Pullman seed bank as an important source of grass and Neotyphodium germplasm for stakeholders.
Technical Abstract: The extent of fungal endophyte (Neotyphodium) based antibiosis resistance in temperate grasses (Lolium spp., Hordeum spp.) to five pestiferous aphid species (Rhopalosiphum padi (L.), Diuraphis noxia (Kurdjumov), Schizaphis graminum (Rondani), Metopolophium dirhodum (Walker), Aploneura lentisci (Passerini)) is briefly described from the literature and by quantification of M. dirhodum densities on different tall fescue (Lolium arundinaceum (Schreb.) S.J. Darbyshire) – Neotyphodium associations in laboratory tests. The literature and new test results show that the magnitude of aphid resistance in endophyte-infected grasses (E+) varies with host grass species/genotype, Neotyphodium strain, alkaloid profile, and aphid species involved in an interaction. Neotyphodium strains that produce alkaloids for insect resistance but little or no mammalian toxins (‘friendly or novel strains’) have been coupled with forage grass cultivars for insect resistance, including novel strain associations with tall fescue and perennial ryegrass (Lolium perenne L.) for host plant resistance to A. lentisci in New Zealand and Australia. Additional uses for grass endophytes in agriculture include potential intercropping of E+ perennial grasses with cereal crops to reduce R. padi acquisition of barley yellow dwarf virus from perennial grasses, thereby reducing aphid vectoring of the virus to cereal crops, and the possible introduction of novel Neotyphodium strains or genetically engineered endophytes into cereal grasses for plant resistance to cereal aphids.