Author
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Clement, Stephen |
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Submitted to: Meeting Abstract
Publication Type: Abstract Only Publication Acceptance Date: 1/21/2000 Publication Date: N/A Citation: N/A Interpretive Summary: None. Technical Abstract: Genetic variation for herbivore resistance in natural plant populations and agricultural plants is often associated with intrinsic factors such as chemical and physical defense mechanisms. Apart from heritable genetic and environmental factors, other factors such as plant microbes mediate host plant-herbivore interactions. For example, the presence of endophytic Neotyphodium fungi in some C3 grasses confers resistance to phytophagous insects through the production of specific alkaloid compounds. However, Neotyphodium infection does not universally confer resistance to insects as revealed by the species-specific nature of aphid resistance in Neotyphodium-infected wild barley (perennial Hordeum spp.). Experimental data show: 1) that the reproduction and survival of Russian wheat aphid (Diuraphis noxia) and rose grass aphid (Metopolophium dirhodum) is adversely affected by some wild barley-Neotyphodium associates, and 2) that twild barley endophytes have no adverse effect on bird cherry-oat aphid, (Rhopalosiphum padi). The endophyte-infected wild barleys originated from the Asian areas of origin of D. noxia (ancestral range of M. dirhodum is unknown). In other experiments, R. padi exhibited differential survival on different tall fescue (Festuca arundinaceae)-Neotyphodium associations originating from non-agricultural settings in Tunisia. The Palearctic home ranges of R. padi and tall fescue overlap. The observed aphid responses were likely the result of variable alkaloid production by an experimental suite of diverse host grass (species, genotype)-Neotyphodium (species, strain) associations. This research documents wide variability in plant- endophyte-insect interactions involving wild host grasses and aphids with overlapping home ranges. |
