Flooding events and rising water temperatures increase the ... · Flooding events and rising water temperatures increase the significance of the reed pathogen Pythium phragmitis Jan
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Flooding events and rising water temperatures increase the significance of the reed pathogen Pythium phragmitis
Jan Nechwatal, Anna Wielgoss, Kurt Mendgen
Universität Konstanz, Phytopathology, Konstanz, Germany
Reed (Phragmites australis)
Perennial grass
Worldwide distribution
Littoral sites, up to 2m deep water
Economic value
Ecological value
ww
w.B
ioLi
b.de
Reed (Phragmites australis)
Lake Constance (Bodensee)Surface area 536 km²Max. depth 254 mShore length 273 kmMax. length 63 kmMax. breadth 14 km
from
: D
iens
t &
Sch
mie
der,
ww
w.b
oden
see-
ufer
.de
Lake Constance reed belt area loss 1998-2000: approx. 24 % (Germany)
Hypotheses:- mechanical damage (recreation, boats, floating debris) - water eutrophication- animal feeding (insects, birds)- reed damage shown to be related to flood duration, time and depth- oxygen deficiency, anaerobic metabolism
„flood-induced reed dieback“ (Ostendorp, Dienst & Schmieder, 2003)
Reed Decline
The Reed Pathogen: Pythium phragmitis
sporangia oospores
Nec
hwat
al e
t al.,
200
5
P. arrhenomanes Drechsler (1928)
The Reed Pathogen: Pythium phragmitis
Grass-associated clusters B1d and B1e(Lévesque & de Cock, 2004)
Van
der
Pla
ats-
Nite
rink,
198
1
Nec
hwat
al e
t al.,
200
5
© J.N.
… to seedlings
P. phragmitis: The Damage it Causes
oospore
… to mature leaves
… no damage to roots and rhizomes infection mainly via leaves
25 plants (6-8 wks. old) per treatment
2000 ml
20 cm
P. phragmitis: The Role of Flooding Events
+ P. phragmitis– P. phragmitis
+ P. phragmitis– P. phragmitis
0
20
40
60
80
100
11 13 15 18 20 22
days post inoculation
% li
ve p
lant
s
Regeneration shooting, 2 wks. after harvesting (= 36 dpi)Control: 5-8 cm per plantPythium: 0
1. plants fully submerged, all leaves below water line, 3 weeks
control
Pythium
P. phragmitis: The Role of Flooding Events
2. plants partly submerged, 50 or 75% of plant height, 4 weeks
0
10
20
30
40
50
Contro
l 50%
Pythium
50%
Contro
l 75%
Pythium
75%
[cm
]
Mean shoot length (live shoots)
0
10
20
30
40
50
contr
ol 50
%
Pythium 5
0%
contr
ol 75
%
Pythium 75
%
% d
ead
shoo
ts
% dead shoots
a ab b
P. phragmitis: The Role of Flooding Events
3. plants clipped before flooding to 6 or 12cm above soil line, 4 weeks
0
2
4
6
8
10
12
14
Contro
l 6
Pythium 6
Contro
l 12
Pythium 12
[cm
]
Mean regenerative shoot length, after 4 wks.
Plant death, after 4 wks.:Control 6: 0Control 12: 0Pythium 6: 36%Pythium 12: 40%
a ab b
P. phragmitis: The Role of Flooding Events
water level 12 cm
water level 6 cm
control Pythium control Pythium
3. plants clipped before flooding to 6 or 12cm above soil line, 4 weeks
P. phragmitis: The Role of Flooding Events
Nec
hwat
al e
t al.,
200
8
Sch
mie
der e
t al.,
200
2: L
imno
logi
ca 3
2, 1
31-1
46
- Reed damage shown to be related to flood duration, time and depth- High susceptibility of submerged leaves to P. phragmitis- No damage in the absence of the pathogen
P. phragmitis as a contributing factor in „flood-induced reed decline“
flood
Mean water level1951-2000
P. phragmitis: The Role of Flooding Events
0
5
10
15
20
25
30
35
6 15 19 25 30 33 37 40temperature [°C]
mm
/ d
growth rate
Straile et al., 2003: Limnol. Oceanogr. 48, 1432–1438
0
2
4
6
8
10
15 18 20 25
Temperature [°C]
Lesi
on le
ngth
[cm
]
leaf necrosis size
0
5
10
15
20
15 20 25
Temperature [°C]
No.
of i
nfec
ted
bait
ends
zoospore production
P. phragmitis: The Influence of Temperature
Nec
hwat
al e
t al.,
200
8: H
ydro
biol
ogia
613
, 109
-115
0
5
10
15
20
25
30M
ärz
Mär
zM
ärz
Apr
ilA
pril
Apr
ilM
aiM
ai
Mai
Juni
Juni
Juni
Juli
Juli
Juli
Aug
ust
Aug
ust
Aug
ust
Sep
tS
ept
Sep
tO
ktO
ktO
kt
Nov
Nov
Nov
Dez
Dez
Dez Jan
Jan
Jan
Jan
°C
Logger 4 TÜ
Logger 8 Ü
Logger 1 T
Logger 2 T
Logger 3 T
Logger 6 Ü
Temperature logger data 2005 (littoral water and sediment)
Mean temperature above 15°C ≈ mean highest lake water line (June – Sept.)optimum infection conditions
P. phragmitis: The Influence of Temperature
young leaves flooded wind-bent, matureplants flooded
- Pythium phragmitis as an aggressive pathogen of common reed
- seedlings as well as mature leaves are susceptible
- negative impact of flooding on reed only in the presence of the pathogen
- flooding periods often equal periods of optimum temperature for the pathogen
- optimum infection conditions
- loss of plant vigour
- losses in reed belt area
- symptoms of reed decline
-`climate change`: effect on flooding events (earlier in the year – younger plants!)
-`climate change`: temperature effect on pathogen (growth, sporulation, virulence)
Flooding events and rising water temperatures increase the significance of the reed pathogen Pythium phragmitis
‚Littoral Zone of Lake Constance‘
The role of fungi during development and decay of reed (Phragmites australis)
Thank you …
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