Grants and Contracts Details
Description
Asexual, seed born endophytes in the genus Neotyphodium are well known for conferring
a wide range of benefits to agronomic grass hosts, like tall fescue and perennial ryegrass.
These benefits include increased resistance to drought, vertebrate and invertebrate
herbivores and seed predators, pathogens and root feeders as well as increasing
germination rates, nutrient uptake, and allelopathic interactions with competitors. The
role of systemic endophytic infections in native pooid grasses, however, is largely
unknown. Many native pooid grasses are infected, but infection frequencies are much
more variable within and between populations and between species than in agronomic
grasses. From past NSF support, we have tested multiple conventional hypotheses
regarding the maintenance and cost and benefits of Neotyphodium infections in Arizona
fescue (Festuca arizonica), a widespread native grass. Our results indicate that the
endophyte does not generally provide the aforementioned benefits to the host under
typical, ambient environments. However, the endophyte does increase growth,
reproduction and competitive abilities, but only at the extreme ranges of water
availability. We propose here to continue this research with Arizona fescue and another
highly infected native grass, sleepy grass (Achnatherum robustum).
Our overarching hypothesis is that the costs and benefits of Neotyphodium infection
depend on plant and endophyte genotypes, water availability, and herbivory. Genotype
and environmental factors, in turn, influence alkaloid production, which is the major
avenue for costs and benefits of infection. We will implement two major field
experiments that control plant genotype and endophyte infection, soil moisture levels and
herbivory by invertebrates and vertebrates. We will also test three other novel and
unconventional hypotheses to explain variability in infections in natural populations.
These include tests of transmission mode of the endophyte, how infection alters sex ratio
of the host plant, and whether Neotyphodium infections allow more pathogenic microbes
to invade the host.
This research is among the first to comprehensively test the cost and benefits of
systemic and symbiotic endophytes in non-agronomic, native grass species. The research
addresses basic questions of how species interactions, especially mutualisms, vary with
genotype and environments. Although basic in nature, the research has important
implications for restoration and maintenance of native semi-arid grasslands, especially
those altered by anthropogenic factors.
Status | Finished |
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Effective start/end date | 2/1/04 → 1/31/05 |
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