o23 nechwatal
DESCRIPTION
2008 Phytophthora Workshop in ItalyTRANSCRIPT
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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
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Reed (Phragmites australis)
Perennial grass
Worldwide distribution
Littoral sites, up to 2m deep water
Economic value
Ecological value
ww
w.B
ioLi
b.de
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Reed (Phragmites australis)
Lake Constance (Bodensee)Surface area 536 km²Max. depth 254 mShore length 273 kmMax. length 63 kmMax. breadth 14 km
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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
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The Reed Pathogen: Pythium phragmitis
sporangia oospores
Nec
hwat
al e
t al.,
200
5
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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
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© J.N.
… to seedlings
P. phragmitis: The Damage it Causes
oospore
… to mature leaves
… no damage to roots and rhizomes infection mainly via leaves
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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
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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
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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
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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
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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
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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
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0
5
10
15
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25
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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
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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
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30M
ärz
Mär
zM
ärz
Apr
ilA
pril
Apr
ilM
aiM
ai
Mai
Juni
Juni
Juni
Juli
Juli
Juli
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tS
ept
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tO
ktO
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kt
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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
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- 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
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‚Littoral Zone of Lake Constance‘
The role of fungi during development and decay of reed (Phragmites australis)
Thank you …