A Multitrophic Interaction between a Fly, a Fungus and Orchardgrass in the Willamette Valley

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A Multitrophic Interaction between a Fly, a
Fungus and Orchardgrass in the Willamette Valley

• Undergraduate Researcher Denise Baumann
• Mentor Dr. Sujaya Rao
• Oregon State University
• Summer 2003

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Orchardgrass in the Willamette Valley

• Dactylis glomerata
• Approx. 20,000 acres in the Willamettte Valley
• Seed Crop
• Forage Crop

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Structure of Grass
Seed Head
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Endophyte Association
Fungal Stroma
Tillers
Seed Stalk
Endophytic Fungi
Single grass plant
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Sexual Development of the Fungus (Egg Hatch)
Spermatial Transfer (Egg Deposition)
Overwintering New growth in Spring (Adult
Emergence)
(Larval Feeding)
Harvest (Pupae Formation)
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Choke in orchardgrass(Epichloe typhina)
Fungal Stoma
Unfertilized
Fertilized Fungus
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Past Research

• Bultman and White (midwest)
• Trials carried out in the wild (isolated grass
  plants)
• 0-7 larvae per fungal stroma
• 63.8 of stromata collected had 1 larva only
  and less than 6 had gt3 larvae per stroma
• Stomata with mesh bag had NO perithecia
  uncovered stromata had 86.6 perithecia
• Fly is necessary for fungal fertilization

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Hypothesis

• In this fly-fungal interaction in orchardgrass in
  the Willamette Valley, the fly is not the sole
  factor for fungal fertilization.

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Objective One

• To determine whether this fly-fungal interaction
  is mutualistic.
• Two treatments
• Fly physically excluded, spore allowed
• Control (no exclusion)

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1
9
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10
2
3
7
4
6
5
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Objective One
Research Plot on Peoria Rd.
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Results
Treatment Fertilization
Exclusion (Fly Only) 56 ns
No Exclusion 69 ns
ns no significant difference
Conclusion The fly is not necessary for fungal
fertilization in a grass field setting here in
the Willamette Valley.
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Objective Two

• Surveying orchardgrass in the Willamette Valley
  to determine the presence of the fly.

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Orchardgrass Sites
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(No Transcript)
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Results

• 0-10 larvae per fungal stroma
• 49.2 of stromata collected had 1 larva/stroma
  and 15 had gt3 larva/stroma
• When 10 larvae were present, gt90 of the
  fertilized stroma was consumed
• 100 of stromata fertilized irrespective of
  larval presence

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Results continued

• Perithecial development at 3 sites
• SR 94 (Average of .62 larva/stroma)
• CH 97 (no fly found at this site)
• RR1 95.7 (Average of 4.16 larva/stroma)

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In Comparison

• My Research
• Shows that there may be other factors besides the
  fly fertilizing the fungus here in the Valley
• 49.2 of stromata collected had 1 larva/stroma
  and 15 had gt3 larva/stroma
• 100 of fungal stroma developed perithecia
  irrespective of fly presence

• Past Research
• Stated that the fly was obligatory for fungal
  fertilization
• 63.8 of stromata collected had 1 larva only and
  less than 6 had gt3 larvae per stroma
• Without presence of the fly 0 fungal stroma
  developed perithecia

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Final Summation
It appears the fly benefits from this interaction
in the Willamette Valley however it is unclear
whether there is a positive or negative effect on
the fungus.
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Future Research

• Preference Studies
• Fungal host preferences by the fly
• Isolation trials
• How does fertilization occur?
• Other factors of fungal fertilization
• Wind, other insects, etc.?

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Acknowledgements

• Howard Hughes Medical Institute (HHMI)
• Undergraduate Research Innovation, Scholarship,
  Creativity (URISC)
• Sujaya Rao, Jon Umble, Devorah Shamah, Bill
  Pfender, Steve Alderman, Mark Mellbye, Glenn
  Fisher, Lynn Royce
• Orchardgrass Growers, especially James VanLeeuwen

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Questions?