Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: September 7, 2000
Publication Date: N/A
Technical Abstract: The presence of Neotyphodium fungi does not confer resistance to all insect associates of infected host grasses. The resistance depends on the alkaloids produced, the host grass species/genotype, the Neotyphoidum species/strain, and the insect species/life stage involved. Our research quantified bird cherry-oat aphid resistance and susceptibility in Mediterranean tall fescue harboring diverse Neotyphoidium genotypes, thereby improving understanding of the variable effects of endophyte infection on insect herbivory. Infection was determined by a PCR test specific for Neotyphodium in tall fescue of diverse geographic origin. The presence of diverse Neotyphodium fungi in this tall fescue was confirmed via conidial measurements and the differential response of aphids on infected accessions. N-coenophialum-infected controls were resistant to aphids and endophyte-free controls were susceptible to aphid reproduction and development in bioassays. In experiments involving tall fescue Sardinia and Morocco, all infected materials were resistant to bird cherry- oat aphid. However, markedly different results were obtained in the experiment involving tall fescue from Tunisia, with some infected accessions supporting significant aphid reproduction and development. Variation in the type and levels of alkaloids produced by some infected tall fescue likely mediated the differential survival of aphids on some Tunisia populations. Thus, resistance to bird cherry-oat aphid in endophyte-infected tall fescue is specific to the Neotyphodium species/ strain and plant population involved in the interaction.