Scholarship at Parkland

Oomycetes are eukaryotic microbes that are pathogenic to plants and animals. Pythiaceae is a family of oomycetes that can infect a variety of hosts causing Pythium Root Rot. Phenotypic differences between isolates of the same species may indicate aggressiveness. These isolates were used in in vitro plate experiments, growth rates, and in oogonia counts. In planta these isolates were used to infect maize from line B73.
Hypotheses:   There is phenotypic diversity across different isolates of oomycetes within the same species when grown on different media. Some phenotypes are correlated with increased disease severity or aggressiveness in maize

Hagemann, Kimberly

Mideros, Santiago

Hall, Harrison

Kimberly Hagemann1, Harrison Hall2, and Santiago Mideros2
1Lincoln Land Community College, Springfield, Illinois 
2Department of Crop Sciences, College of ACES, University of Illinois at Urbana-Champaign
In Vitro Phenotypes of Pythium Isolates are Correlated with Disease Symptoms in the Greenhouse
Acknowledgments
Financial support was provided by the National Science Foundation under grant #NSF 
REU 1950819/1950786, as part of the Phenotypic Plasticity Research Experience for 
Community College Students, through the University of Illinois at Urbana-Champaign 
Institute for Genomic Biology and Parkland College. http://precs.igb.illinois.edu/
I would like to thank the Mideros and Jamann labs for helping me along 
the way. Especially my mentor, Harrison Hall. Also, I would like to thank my family and 
friends for always supporting me.
References
Kamoun, S., Furzer, O., Jones, J. D. G., Judelson, H. S., Ali, G. S., Dalio, R. J. D., Roy, S. 
G., Schena, L., Zambounis, A., Panabières, F., Cahill, D., Ruocco, M., Figueiredo, A., 
Chen, X.-R., Hulvey, J., Stam, R., Lamour, K., Gijzen, M., Tyler, B. M., … Govers, F. 
(2015). The Top 10 oomycete pathogens in molecular plant pathology. Molecular 
Plant Pathology, 16(4), Article 4. https://doi.org/10.1111/mpp.12190
Van Der Plaats-Niterink, J. (1981, December 22). Monograph of the genus Pythium. 
Studies in Mycology. No. 21, Centraalbureau Voor Schimmelcultures, Baarn. 
https://www.studiesinmycology.org/sim/Sim21/full%20text.htm
Introduction
Oomycetes are eukaryotic microbes that are pathogenic to 
plants and animals. Pythiaceae is a family of oomycetes that can 
infect a variety of hosts causing Pythium Root Rot. Phenotypic 
differences between isolates of the same species may 
indicate aggressiveness. These isolates were used in in 
vitro plate experiments, growth rates, and in oogonia counts. In 
planta these isolates were used to infect maize from line B73.
 
Hypotheses:
• There is phenotypic diversity across different 
isolates of oomycetes within the same species 
when grown on different media.
• Some phenotypes are correlated with 
increased disease severity or aggressiveness 
in maize.
Material and Methods
9 isolates were available: 2 isolates from Pythium irregulare, 
2 isolates from P. aphanidermatum, 3 isolates from P. ultimum 
var. ultimum, and 2 isolates from Phytophthora sojae (Non-
pathogen on maize).
In vitro assay:
 Media: lima bean V8, potato carrot, potato dextrose, 
cornmeal agar.
 Growth rate: Isolates grown on PDA or LBDV8 for P. sojae, 
measured daily with callipers, slope & total growth analyzed
 Oogonia count: Potato carrot agar plates, measured with 
microscope and hand counter.
In planta assay:
 • 9 isolates + 1 control: 10 flasks of inoculated cornmeal and 
sand mixture
 • Conetainers, pots, coffee filters, aluminium foil, B73 seeds
 • Grown 11 days on BM2 soil, measured root lengths, 
masses, disease severity
 
  Figure 1: One replication of in vitro plate experiment
Analysis: 
ANOVA in R Studio measured phenotype differences. TukeyHSD 
determined significance between isolates and species. cor.test 
assessed phenotype correlations. Data were normal.
 Significance codes:  
p < 0.001 = ‘***’ ; p < 0.01 = ‘**’ ; p < 0.05 = ‘*’ ;  p < 0.1 = ‘.’
Conclusions
• Significant difference of growth rates 
between isolates of P. ultimum var. ultimum; 
significant difference of oogonia production 
between isolates of P. aphanidermatum
 
• Oogonia production was significantly 
correlated with disease in plants: more 
oogonia associated with less disease  
 
• Faster in vitro growth rate was significantly 
correlated with disease in plants: slower in 
vitro growth associated with more disease
Figure 4 (right): 120 seeds of B73 were inoculated and 
planted into conetainers in the greenhouse. (A) Infected 
seedling compared control. (B) Percent root necrosis, 
controls were less diseased than inoculated. (C) Root 
lengths as a percent of mock inoculated controls.
(D) Root mass as a percent of mock inoculated controls
Figure 2: (A) Oogonia counts by isolate separated by species, P. aphanidermatum isolates were significantly different. (B) P. irregulare 
darkened circle around older growth. (C) Oogonia under microscope. 
Future Work
• Additional replications using more isolates and species 
of Pythium & Globisporangium
• Continuing Koch’s Postulates with greenhouse plants
B
A
In vitro oogonia counts
In Planta greenhouse phenotypes 
Figure 3: Race tubes were used to measure growth rate (A) Depicts sample size. (B) Growth rate of all isolates after 10 days, letters in 
legend adjacent to isolate ID indicate significant differences between isolates. (C) Diseased greenhouse plant inoculated with 
17PR013A (left) next to mock-inoculated control (right). (D) Total growth of isolates by species, letters below species name indicate 
significant differences of growth rate between species.
C
A Control
Inoculated
***
0
25000
50000
75000
100000
Oogonia count per plate by isolate
Phytophthora sojae
(Non-pathogen control)
Pythium aphanidermatum P. irregulare P. ultimum var. ultimum
A
In vitro growth rates
0
50
100
150
200
1 3 5 7 9
T
o
ta
l 
G
ro
w
th
 P
e
r 
D
a
y
 (
m
m
)
Average Total Growth per Day by Isolate
a a
b
b
c
c
d
e
e
P. irregulare P. ultimum var. ultimum
Phytophthora sojae P. aphanidermatum
1 3 5 7 9 1 3 5 7 9
0
50
100
150
200
0
50
100
150
200
T
o
ta
l 
G
ro
w
th
 P
e
r 
D
a
y
 (
m
m
)
Average Total Growth per Day 
by Species and Isolate
a b
c d
D
B
0
50
100
150
200
Root mass as a percent of control - by isolate
Control P. aphanidermatum P. irregulare P. ultimum var. ultimum Phytophthora sojae (Non-pathogen on maize)
0
50
100
150
Root length as a percent of control - by isolate
0
30
60
90
% Root necrosis by isolate
Figure 5 : Significant correlations were found between 
root phenotypes; root length with in vitro phenotypes. 
B C D
r = 0.83
p = 0.000
r = 0.71
p = 0.000
r = 0.32
p = 0.005
r = -0.26
p = 0.027
r = 0.77
p = 0.000
r = 0.16
p = 0.175
r = -0.15
p = 0.207
r = 0.17
p = 0.134
r = -0.13
p = 0.277
r = -0.56
p = 0.000
Root 
Length
Root 
Mass
% Root 
Necrosis
Oogonia 
Per Plate
Race Tube 
Growth 
Rate
R
o
o
t 
L
e
n
g
th
R
o
o
t 
M
a
s
s
%
 R
o
o
t 
N
e
c
ro
s
is O
o
g
o
n
ia
 
P
e
r 
P
la
te
R
a
c
e
 T
u
b
e
 
G
ro
w
th
 R
a
te
Correlation and P-Values
***
*** ***
**
* ***
Isolate
16PR010.1
17PR004J.1
17PR007A
17PR010.C.1
17PR011G
17PR013A
17PR016B
18PR001
Pi354
C


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