1. 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

2. Orchardgrass in the Willamette Valley
Dactylis glomerata
Approx. 20,000 acres in the Willamettte Valley
Seed Crop
Forage Crop

3. Structure of Grass Seed Head Blade (leaf) Tillers Seed Stalk
Single grass plant
Seed Stalk
Tillers
Blade (leaf)

4. Endophyte Association
Fungal Stroma
Tillers
Seed Stalk
Endophytic Fungi
Single grass plant

5. - - + Sexual Development of the Fungus (Egg Hatch) Spermatial Transfer
(Egg Deposition) +
Overwintering &
New growth in Spring
(Adult Emergence)
(Larval Feeding)
Harvest
(Pupae Formation)

6. Choke in orchardgrass (Epichloe typhina)
Fungal Stoma
Unfertilized
Fertilized Fungus

7. 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 >3 larvae per stroma
Stomata with mesh bag had NO perithecia; uncovered stromata had 86.6 % perithecia
Fly is necessary for fungal fertilization

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

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

10. 1 9 8 10 2 3 7 4 6 5

11. Research Plot on Peoria Rd.
Objective One
Research Plot on Peoria Rd.

12. 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.

13. Objective Two
Surveying orchardgrass in the Willamette Valley to determine the presence of the fly.

14. Orchardgrass Sites Corvallis Benton Co. Linn Co. Lane Co. SR HP LR CHWD AD KR IB PR ND
RR3
RR2
RR1

16. Results 0-10 larvae per fungal stroma
49.2 % of stromata collected had 1 larva/stroma and 15 % had >3 larva/stroma
When 10 larvae were present, >90% of the fertilized stroma was consumed
100 % of stromata fertilized irrespective of larval presence

17. 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)

18. In Comparison… My Research 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 >3 larvae per stroma
Without presence of the fly 0% fungal stroma developed perithecia
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 >3 larva/stroma
100% of fungal stroma developed perithecia irrespective of fly presence

19. 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.

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

21. 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

22. Questions?