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
Orchardgrass in the
Willamette Valley

Dactylis
glomerata

Approx. 20,000
acres in the
Willamettte
Valley


Seed Crop
Forage Crop
Structure of Grass
Blade (leaf)
Seed
Head
Tillers
Seed
Stalk
Single grass plant
Endophyte Association
Fungal
Stroma
Tillers
Seed
Stalk
Endophytic
Fungi
Single grass plant
Sexual Development
of the Fungus
Spermatial
Transfer
-- -
(Egg Hatch)
(Egg Deposition)
-- -
++ ++
Overwintering &
New growth in Spring
(Adult Emergence)
(Larval Feeding)
Harvest
(Pupae Formation)
Choke in orchardgrass
(Epichloe typhina)
Fungal Stoma
Unfertilized
Fertilized Fungus
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
Hypothesis
In this fly-fungal interaction in orchardgrass in the
Willamette Valley, the fly is not the sole factor
for fungal fertilization.
Objective One

To determine whether this flyfungal interaction is mutualistic.

Two treatments
1.
Fly physically excluded, spore allowed
2.
Control (no exclusion)
1
9
10
8
2
3
7
4
6
5
Objective One
Research Plot on Peoria Rd.
Results
Treatment
Exclusion
(Fly Only)
No Exclusion
% Fertilization
56%
ns
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.
Objective Two

Surveying orchardgrass in the
Willamette Valley to determine the
presence of the fly.
Orchardgrass Sites
LR
HP
CH
SR
Corvallis
WD
Benton Co.
PR
AD
IB
KR
RR3
Lane Co.
RR1
RR2
Linn Co.
Relationship between Avg Larva/stroma and % Larval infestation
60
4.5
4
50
40
3
2.5
30
2
20
1.5
1
10
0.5
0
0
RR1 RR2
KR
SR
WD
IB
HP
RR3
LR
AD
Field Site
Larval Infested Stroma
AvgLar/stroma
PR
ND
CH
AvgLar/Stroma
Larval Infestation
3.5
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
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)
In Comparison…

Past Research
1.
2.
3.
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
1.
2.
3.
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
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.
Future Research

Preference Studies


Isolation trials


Fungal host preferences by the fly
How does fertilization occur?
Other factors of fungal fertilization

Wind, other insects, etc.?
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
Questions?